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729eb14ae8
"I have been working my way through the JIT and Kaleidoscope tutorials in my (minuscule) spare time. Thanks again for writing them! I have attached a patch containing some minor changes, ranging from spelling and grammar fixes to adding a "Next: <next tutorial section>" hyperlink to the bottom of each page. Every page has been given the "next link" treatment, but otherwise I'm only half way through the Kaleidoscope tutorial. I will send a follow-on patch if time permits." git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46933 91177308-0d34-0410-b5e6-96231b3b80d8
2160 lines
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HTML
2160 lines
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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"http://www.w3.org/TR/html4/strict.dtd">
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<html>
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<head>
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<title>Kaleidoscope: Extending the Language: Mutable Variables / SSA
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construction</title>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<meta name="author" content="Chris Lattner">
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<link rel="stylesheet" href="../llvm.css" type="text/css">
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</head>
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<body>
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<div class="doc_title">Kaleidoscope: Extending the Language: Mutable Variables</div>
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<ul>
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<li><a href="index.html">Up to Tutorial Index</a></li>
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<li>Chapter 7
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<ol>
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<li><a href="#intro">Chapter 7 Introduction</a></li>
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<li><a href="#why">Why is this a hard problem?</a></li>
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<li><a href="#memory">Memory in LLVM</a></li>
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<li><a href="#kalvars">Mutable Variables in Kaleidoscope</a></li>
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<li><a href="#adjustments">Adjusting Existing Variables for
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Mutation</a></li>
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<li><a href="#assignment">New Assignment Operator</a></li>
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<li><a href="#localvars">User-defined Local Variables</a></li>
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<li><a href="#code">Full Code Listing</a></li>
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</ol>
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</li>
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<li><a href="LangImpl8.html">Chapter 8</a>: Conclusion and other useful LLVM
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tidbits</li>
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</ul>
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<div class="doc_author">
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<p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a></p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section"><a name="intro">Chapter 7 Introduction</a></div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>Welcome to Chapter 7 of the "<a href="index.html">Implementing a language
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with LLVM</a>" tutorial. In chapters 1 through 6, we've built a very
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respectable, albeit simple, <a
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href="http://en.wikipedia.org/wiki/Functional_programming">functional
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programming language</a>. In our journey, we learned some parsing techniques,
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how to build and represent an AST, how to build LLVM IR, and how to optimize
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the resultant code as well as JIT compile it.</p>
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<p>While Kaleidoscope is interesting as a functional language, the fact that it
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is functional makes it "too easy" to generate LLVM IR for it. In particular, a
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functional language makes it very easy to build LLVM IR directly in <a
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href="http://en.wikipedia.org/wiki/Static_single_assignment_form">SSA form</a>.
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Since LLVM requires that the input code be in SSA form, this is a very nice
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property and it is often unclear to newcomers how to generate code for an
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imperative language with mutable variables.</p>
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<p>The short (and happy) summary of this chapter is that there is no need for
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your front-end to build SSA form: LLVM provides highly tuned and well tested
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support for this, though the way it works is a bit unexpected for some.</p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section"><a name="why">Why is this a hard problem?</a></div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>
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To understand why mutable variables cause complexities in SSA construction,
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consider this extremely simple C example:
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</p>
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<div class="doc_code">
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<pre>
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int G, H;
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int test(_Bool Condition) {
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int X;
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if (Condition)
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X = G;
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else
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X = H;
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return X;
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}
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</pre>
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</div>
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<p>In this case, we have the variable "X", whose value depends on the path
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executed in the program. Because there are two different possible values for X
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before the return instruction, a PHI node is inserted to merge the two values.
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The LLVM IR that we want for this example looks like this:</p>
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<div class="doc_code">
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<pre>
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@G = weak global i32 0 ; type of @G is i32*
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@H = weak global i32 0 ; type of @H is i32*
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define i32 @test(i1 %Condition) {
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entry:
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br i1 %Condition, label %cond_true, label %cond_false
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cond_true:
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%X.0 = load i32* @G
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br label %cond_next
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cond_false:
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%X.1 = load i32* @H
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br label %cond_next
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cond_next:
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%X.2 = phi i32 [ %X.1, %cond_false ], [ %X.0, %cond_true ]
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ret i32 %X.2
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}
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</pre>
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</div>
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<p>In this example, the loads from the G and H global variables are explicit in
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the LLVM IR, and they live in the then/else branches of the if statement
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(cond_true/cond_false). In order to merge the incoming values, the X.2 phi node
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in the cond_next block selects the right value to use based on where control
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flow is coming from: if control flow comes from the cond_false block, X.2 gets
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the value of X.1. Alternatively, if control flow comes from cond_true, it gets
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the value of X.0. The intent of this chapter is not to explain the details of
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SSA form. For more information, see one of the many <a
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href="http://en.wikipedia.org/wiki/Static_single_assignment_form">online
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references</a>.</p>
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<p>The question for this article is "who places the phi nodes when lowering
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assignments to mutable variables?". The issue here is that LLVM
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<em>requires</em> that its IR be in SSA form: there is no "non-ssa" mode for it.
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However, SSA construction requires non-trivial algorithms and data structures,
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so it is inconvenient and wasteful for every front-end to have to reproduce this
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logic.</p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section"><a name="memory">Memory in LLVM</a></div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>The 'trick' here is that while LLVM does require all register values to be
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in SSA form, it does not require (or permit) memory objects to be in SSA form.
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In the example above, note that the loads from G and H are direct accesses to
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G and H: they are not renamed or versioned. This differs from some other
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compiler systems, which do try to version memory objects. In LLVM, instead of
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encoding dataflow analysis of memory into the LLVM IR, it is handled with <a
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href="../WritingAnLLVMPass.html">Analysis Passes</a> which are computed on
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demand.</p>
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<p>
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With this in mind, the high-level idea is that we want to make a stack variable
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(which lives in memory, because it is on the stack) for each mutable object in
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a function. To take advantage of this trick, we need to talk about how LLVM
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represents stack variables.
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</p>
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<p>In LLVM, all memory accesses are explicit with load/store instructions, and
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it is carefully designed not to have (or need) an "address-of" operator. Notice
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how the type of the @G/@H global variables is actually "i32*" even though the
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variable is defined as "i32". What this means is that @G defines <em>space</em>
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for an i32 in the global data area, but its <em>name</em> actually refers to the
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address for that space. Stack variables work the same way, except that instead of
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being declared with global variable definitions, they are declared with the
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<a href="../LangRef.html#i_alloca">LLVM alloca instruction</a>:</p>
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<div class="doc_code">
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<pre>
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define i32 @example() {
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entry:
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%X = alloca i32 ; type of %X is i32*.
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...
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%tmp = load i32* %X ; load the stack value %X from the stack.
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%tmp2 = add i32 %tmp, 1 ; increment it
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store i32 %tmp2, i32* %X ; store it back
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...
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</pre>
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</div>
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<p>This code shows an example of how you can declare and manipulate a stack
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variable in the LLVM IR. Stack memory allocated with the alloca instruction is
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fully general: you can pass the address of the stack slot to functions, you can
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store it in other variables, etc. In our example above, we could rewrite the
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example to use the alloca technique to avoid using a PHI node:</p>
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<div class="doc_code">
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<pre>
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@G = weak global i32 0 ; type of @G is i32*
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@H = weak global i32 0 ; type of @H is i32*
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define i32 @test(i1 %Condition) {
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entry:
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%X = alloca i32 ; type of %X is i32*.
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br i1 %Condition, label %cond_true, label %cond_false
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cond_true:
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%X.0 = load i32* @G
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store i32 %X.0, i32* %X ; Update X
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br label %cond_next
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cond_false:
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%X.1 = load i32* @H
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store i32 %X.1, i32* %X ; Update X
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br label %cond_next
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cond_next:
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%X.2 = load i32* %X ; Read X
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ret i32 %X.2
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}
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</pre>
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</div>
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<p>With this, we have discovered a way to handle arbitrary mutable variables
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without the need to create Phi nodes at all:</p>
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<ol>
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<li>Each mutable variable becomes a stack allocation.</li>
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<li>Each read of the variable becomes a load from the stack.</li>
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<li>Each update of the variable becomes a store to the stack.</li>
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<li>Taking the address of a variable just uses the stack address directly.</li>
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</ol>
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<p>While this solution has solved our immediate problem, it introduced another
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one: we have now apparently introduced a lot of stack traffic for very simple
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and common operations, a major performance problem. Fortunately for us, the
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LLVM optimizer has a highly-tuned optimization pass named "mem2reg" that handles
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this case, promoting allocas like this into SSA registers, inserting Phi nodes
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as appropriate. If you run this example through the pass, for example, you'll
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get:</p>
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<div class="doc_code">
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<pre>
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$ <b>llvm-as < example.ll | opt -mem2reg | llvm-dis</b>
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@G = weak global i32 0
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@H = weak global i32 0
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define i32 @test(i1 %Condition) {
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entry:
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br i1 %Condition, label %cond_true, label %cond_false
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cond_true:
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%X.0 = load i32* @G
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br label %cond_next
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cond_false:
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%X.1 = load i32* @H
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br label %cond_next
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cond_next:
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%X.01 = phi i32 [ %X.1, %cond_false ], [ %X.0, %cond_true ]
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ret i32 %X.01
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}
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</pre>
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</div>
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<p>The mem2reg pass implements the standard "iterated dominance frontier"
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algorithm for constructing SSA form and has a number of optimizations that speed
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up (very common) degenerate cases. The mem2reg optimization pass is the answer to dealing
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with mutable variables, and we highly recommend that you depend on it. Note that
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mem2reg only works on variables in certain circumstances:</p>
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<ol>
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<li>mem2reg is alloca-driven: it looks for allocas and if it can handle them, it
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promotes them. It does not apply to global variables or heap allocations.</li>
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<li>mem2reg only looks for alloca instructions in the entry block of the
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function. Being in the entry block guarantees that the alloca is only executed
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once, which makes analysis simpler.</li>
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<li>mem2reg only promotes allocas whose uses are direct loads and stores. If
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the address of the stack object is passed to a function, or if any funny pointer
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arithmetic is involved, the alloca will not be promoted.</li>
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<li>mem2reg only works on allocas of <a
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href="../LangRef.html#t_classifications">first class</a>
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values (such as pointers, scalars and vectors), and only if the array size
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of the allocation is 1 (or missing in the .ll file). mem2reg is not capable of
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promoting structs or arrays to registers. Note that the "scalarrepl" pass is
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more powerful and can promote structs, "unions", and arrays in many cases.</li>
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</ol>
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<p>
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All of these properties are easy to satisfy for most imperative languages, and
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we'll illustrate it below with Kaleidoscope. The final question you may be
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asking is: should I bother with this nonsense for my front-end? Wouldn't it be
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better if I just did SSA construction directly, avoiding use of the mem2reg
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optimization pass? In short, we strongly recommend that you use this technique
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for building SSA form, unless there is an extremely good reason not to. Using
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this technique is:</p>
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<ul>
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<li>Proven and well tested: llvm-gcc and clang both use this technique for local
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mutable variables. As such, the most common clients of LLVM are using this to
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handle a bulk of their variables. You can be sure that bugs are found fast and
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fixed early.</li>
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<li>Extremely Fast: mem2reg has a number of special cases that make it fast in
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common cases as well as fully general. For example, it has fast-paths for
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variables that are only used in a single block, variables that only have one
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assignment point, good heuristics to avoid insertion of unneeded phi nodes, etc.
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</li>
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<li>Needed for debug info generation: <a href="../SourceLevelDebugging.html">
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Debug information in LLVM</a> relies on having the address of the variable
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exposed so that debug info can be attached to it. This technique dovetails
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very naturally with this style of debug info.</li>
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</ul>
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<p>If nothing else, this makes it much easier to get your front-end up and
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running, and is very simple to implement. Lets extend Kaleidoscope with mutable
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variables now!
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</p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section"><a name="kalvars">Mutable Variables in
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Kaleidoscope</a></div>
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<!-- *********************************************************************** -->
|
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<div class="doc_text">
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<p>Now that we know the sort of problem we want to tackle, lets see what this
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looks like in the context of our little Kaleidoscope language. We're going to
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add two features:</p>
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<ol>
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<li>The ability to mutate variables with the '=' operator.</li>
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<li>The ability to define new variables.</li>
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|
</ol>
|
|
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<p>While the first item is really what this is about, we only have variables
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for incoming arguments as well as for induction variables, and redefining those only
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goes so far :). Also, the ability to define new variables is a
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useful thing regardless of whether you will be mutating them. Here's a
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motivating example that shows how we could use these:</p>
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<div class="doc_code">
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<pre>
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# Define ':' for sequencing: as a low-precedence operator that ignores operands
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# and just returns the RHS.
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def binary : 1 (x y) y;
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# Recursive fib, we could do this before.
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def fib(x)
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if (x < 3) then
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1
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else
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fib(x-1)+fib(x-2);
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|
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# Iterative fib.
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def fibi(x)
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<b>var a = 1, b = 1, c in</b>
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(for i = 3, i < x in
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<b>c = a + b</b> :
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<b>a = b</b> :
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<b>b = c</b>) :
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b;
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# Call it.
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fibi(10);
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</pre>
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</div>
|
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<p>
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In order to mutate variables, we have to change our existing variables to use
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the "alloca trick". Once we have that, we'll add our new operator, then extend
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Kaleidoscope to support new variable definitions.
|
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</p>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
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<div class="doc_section"><a name="adjustments">Adjusting Existing Variables for
|
|
Mutation</a></div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>
|
|
The symbol table in Kaleidoscope is managed at code generation time by the
|
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'<tt>NamedValues</tt>' map. This map currently keeps track of the LLVM "Value*"
|
|
that holds the double value for the named variable. In order to support
|
|
mutation, we need to change this slightly, so that it <tt>NamedValues</tt> holds
|
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the <em>memory location</em> of the variable in question. Note that this
|
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change is a refactoring: it changes the structure of the code, but does not
|
|
(by itself) change the behavior of the compiler. All of these changes are
|
|
isolated in the Kaleidoscope code generator.</p>
|
|
|
|
<p>
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|
At this point in Kaleidoscope's development, it only supports variables for two
|
|
things: incoming arguments to functions and the induction variable of 'for'
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|
loops. For consistency, we'll allow mutation of these variables in addition to
|
|
other user-defined variables. This means that these will both need memory
|
|
locations.
|
|
</p>
|
|
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<p>To start our transformation of Kaleidoscope, we'll change the NamedValues
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|
map so that it maps to AllocaInst* instead of Value*. Once we do this, the C++
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compiler will tell us what parts of the code we need to update:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
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|
static std::map<std::string, AllocaInst*> NamedValues;
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</pre>
|
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</div>
|
|
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<p>Also, since we will need to create these alloca's, we'll use a helper
|
|
function that ensures that the allocas are created in the entry block of the
|
|
function:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
/// CreateEntryBlockAlloca - Create an alloca instruction in the entry block of
|
|
/// the function. This is used for mutable variables etc.
|
|
static AllocaInst *CreateEntryBlockAlloca(Function *TheFunction,
|
|
const std::string &VarName) {
|
|
LLVMBuilder TmpB(&TheFunction->getEntryBlock(),
|
|
TheFunction->getEntryBlock().begin());
|
|
return TmpB.CreateAlloca(Type::DoubleTy, 0, VarName.c_str());
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}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>This funny looking code creates an LLVMBuilder object that is pointing at
|
|
the first instruction (.begin()) of the entry block. It then creates an alloca
|
|
with the expected name and returns it. Because all values in Kaleidoscope are
|
|
doubles, there is no need to pass in a type to use.</p>
|
|
|
|
<p>With this in place, the first functionality change we want to make is to
|
|
variable references. In our new scheme, variables live on the stack, so code
|
|
generating a reference to them actually needs to produce a load from the stack
|
|
slot:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
Value *VariableExprAST::Codegen() {
|
|
// Look this variable up in the function.
|
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Value *V = NamedValues[Name];
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|
if (V == 0) return ErrorV("Unknown variable name");
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|
|
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<b>// Load the value.
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return Builder.CreateLoad(V, Name.c_str());</b>
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}
|
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</pre>
|
|
</div>
|
|
|
|
<p>As you can see, this is pretty straightforward. Now we need to update the
|
|
things that define the variables to set up the alloca. We'll start with
|
|
<tt>ForExprAST::Codegen</tt> (see the <a href="#code">full code listing</a> for
|
|
the unabridged code):</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
Function *TheFunction = Builder.GetInsertBlock()->getParent();
|
|
|
|
<b>// Create an alloca for the variable in the entry block.
|
|
AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);</b>
|
|
|
|
// Emit the start code first, without 'variable' in scope.
|
|
Value *StartVal = Start->Codegen();
|
|
if (StartVal == 0) return 0;
|
|
|
|
<b>// Store the value into the alloca.
|
|
Builder.CreateStore(StartVal, Alloca);</b>
|
|
...
|
|
|
|
// Compute the end condition.
|
|
Value *EndCond = End->Codegen();
|
|
if (EndCond == 0) return EndCond;
|
|
|
|
<b>// Reload, increment, and restore the alloca. This handles the case where
|
|
// the body of the loop mutates the variable.
|
|
Value *CurVar = Builder.CreateLoad(Alloca);
|
|
Value *NextVar = Builder.CreateAdd(CurVar, StepVal, "nextvar");
|
|
Builder.CreateStore(NextVar, Alloca);</b>
|
|
...
|
|
</pre>
|
|
</div>
|
|
|
|
<p>This code is virtually identical to the code <a
|
|
href="LangImpl5.html#forcodegen">before we allowed mutable variables</a>. The
|
|
big difference is that we no longer have to construct a PHI node, and we use
|
|
load/store to access the variable as needed.</p>
|
|
|
|
<p>To support mutable argument variables, we need to also make allocas for them.
|
|
The code for this is also pretty simple:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
/// CreateArgumentAllocas - Create an alloca for each argument and register the
|
|
/// argument in the symbol table so that references to it will succeed.
|
|
void PrototypeAST::CreateArgumentAllocas(Function *F) {
|
|
Function::arg_iterator AI = F->arg_begin();
|
|
for (unsigned Idx = 0, e = Args.size(); Idx != e; ++Idx, ++AI) {
|
|
// Create an alloca for this variable.
|
|
AllocaInst *Alloca = CreateEntryBlockAlloca(F, Args[Idx]);
|
|
|
|
// Store the initial value into the alloca.
|
|
Builder.CreateStore(AI, Alloca);
|
|
|
|
// Add arguments to variable symbol table.
|
|
NamedValues[Args[Idx]] = Alloca;
|
|
}
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>For each argument, we make an alloca, store the input value to the function
|
|
into the alloca, and register the alloca as the memory location for the
|
|
argument. This method gets invoked by <tt>FunctionAST::Codegen</tt> right after
|
|
it sets up the entry block for the function.</p>
|
|
|
|
<p>The final missing piece is adding the mem2reg pass, which allows us to get
|
|
good codegen once again:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
// Set up the optimizer pipeline. Start with registering info about how the
|
|
// target lays out data structures.
|
|
OurFPM.add(new TargetData(*TheExecutionEngine->getTargetData()));
|
|
<b>// Promote allocas to registers.
|
|
OurFPM.add(createPromoteMemoryToRegisterPass());</b>
|
|
// Do simple "peephole" optimizations and bit-twiddling optzns.
|
|
OurFPM.add(createInstructionCombiningPass());
|
|
// Reassociate expressions.
|
|
OurFPM.add(createReassociatePass());
|
|
</pre>
|
|
</div>
|
|
|
|
<p>It is interesting to see what the code looks like before and after the
|
|
mem2reg optimization runs. For example, this is the before/after code for our
|
|
recursive fib function. Before the optimization:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
define double @fib(double %x) {
|
|
entry:
|
|
<b>%x1 = alloca double
|
|
store double %x, double* %x1
|
|
%x2 = load double* %x1</b>
|
|
%cmptmp = fcmp ult double %x2, 3.000000e+00
|
|
%booltmp = uitofp i1 %cmptmp to double
|
|
%ifcond = fcmp one double %booltmp, 0.000000e+00
|
|
br i1 %ifcond, label %then, label %else
|
|
|
|
then: ; preds = %entry
|
|
br label %ifcont
|
|
|
|
else: ; preds = %entry
|
|
<b>%x3 = load double* %x1</b>
|
|
%subtmp = sub double %x3, 1.000000e+00
|
|
%calltmp = call double @fib( double %subtmp )
|
|
<b>%x4 = load double* %x1</b>
|
|
%subtmp5 = sub double %x4, 2.000000e+00
|
|
%calltmp6 = call double @fib( double %subtmp5 )
|
|
%addtmp = add double %calltmp, %calltmp6
|
|
br label %ifcont
|
|
|
|
ifcont: ; preds = %else, %then
|
|
%iftmp = phi double [ 1.000000e+00, %then ], [ %addtmp, %else ]
|
|
ret double %iftmp
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Here there is only one variable (x, the input argument) but you can still
|
|
see the extremely simple-minded code generation strategy we are using. In the
|
|
entry block, an alloca is created, and the initial input value is stored into
|
|
it. Each reference to the variable does a reload from the stack. Also, note
|
|
that we didn't modify the if/then/else expression, so it still inserts a PHI
|
|
node. While we could make an alloca for it, it is actually easier to create a
|
|
PHI node for it, so we still just make the PHI.</p>
|
|
|
|
<p>Here is the code after the mem2reg pass runs:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
define double @fib(double %x) {
|
|
entry:
|
|
%cmptmp = fcmp ult double <b>%x</b>, 3.000000e+00
|
|
%booltmp = uitofp i1 %cmptmp to double
|
|
%ifcond = fcmp one double %booltmp, 0.000000e+00
|
|
br i1 %ifcond, label %then, label %else
|
|
|
|
then:
|
|
br label %ifcont
|
|
|
|
else:
|
|
%subtmp = sub double <b>%x</b>, 1.000000e+00
|
|
%calltmp = call double @fib( double %subtmp )
|
|
%subtmp5 = sub double <b>%x</b>, 2.000000e+00
|
|
%calltmp6 = call double @fib( double %subtmp5 )
|
|
%addtmp = add double %calltmp, %calltmp6
|
|
br label %ifcont
|
|
|
|
ifcont: ; preds = %else, %then
|
|
%iftmp = phi double [ 1.000000e+00, %then ], [ %addtmp, %else ]
|
|
ret double %iftmp
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>This is a trivial case for mem2reg, since there are no redefinitions of the
|
|
variable. The point of showing this is to calm your tension about inserting
|
|
such blatent inefficiencies :).</p>
|
|
|
|
<p>After the rest of the optimizers run, we get:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
define double @fib(double %x) {
|
|
entry:
|
|
%cmptmp = fcmp ult double %x, 3.000000e+00
|
|
%booltmp = uitofp i1 %cmptmp to double
|
|
%ifcond = fcmp ueq double %booltmp, 0.000000e+00
|
|
br i1 %ifcond, label %else, label %ifcont
|
|
|
|
else:
|
|
%subtmp = sub double %x, 1.000000e+00
|
|
%calltmp = call double @fib( double %subtmp )
|
|
%subtmp5 = sub double %x, 2.000000e+00
|
|
%calltmp6 = call double @fib( double %subtmp5 )
|
|
%addtmp = add double %calltmp, %calltmp6
|
|
ret double %addtmp
|
|
|
|
ifcont:
|
|
ret double 1.000000e+00
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Here we see that the simplifycfg pass decided to clone the return instruction
|
|
into the end of the 'else' block. This allowed it to eliminate some branches
|
|
and the PHI node.</p>
|
|
|
|
<p>Now that all symbol table references are updated to use stack variables,
|
|
we'll add the assignment operator.</p>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section"><a name="assignment">New Assignment Operator</a></div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>With our current framework, adding a new assignment operator is really
|
|
simple. We will parse it just like any other binary operator, but handle it
|
|
internally (instead of allowing the user to define it). The first step is to
|
|
set a precedence:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
int main() {
|
|
// Install standard binary operators.
|
|
// 1 is lowest precedence.
|
|
<b>BinopPrecedence['='] = 2;</b>
|
|
BinopPrecedence['<'] = 10;
|
|
BinopPrecedence['+'] = 20;
|
|
BinopPrecedence['-'] = 20;
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Now that the parser knows the precedence of the binary operator, it takes
|
|
care of all the parsing and AST generation. We just need to implement codegen
|
|
for the assignment operator. This looks like:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
Value *BinaryExprAST::Codegen() {
|
|
// Special case '=' because we don't want to emit the LHS as an expression.
|
|
if (Op == '=') {
|
|
// Assignment requires the LHS to be an identifier.
|
|
VariableExprAST *LHSE = dynamic_cast<VariableExprAST*>(LHS);
|
|
if (!LHSE)
|
|
return ErrorV("destination of '=' must be a variable");
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Unlike the rest of the binary operators, our assignment operator doesn't
|
|
follow the "emit LHS, emit RHS, do computation" model. As such, it is handled
|
|
as a special case before the other binary operators are handled. The other
|
|
strange thing is that it requires the LHS to be a variable. It is invalid to
|
|
have "(x+1) = expr" - only things like "x = expr" are allowed.
|
|
</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
// Codegen the RHS.
|
|
Value *Val = RHS->Codegen();
|
|
if (Val == 0) return 0;
|
|
|
|
// Look up the name.
|
|
Value *Variable = NamedValues[LHSE->getName()];
|
|
if (Variable == 0) return ErrorV("Unknown variable name");
|
|
|
|
Builder.CreateStore(Val, Variable);
|
|
return Val;
|
|
}
|
|
...
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Once we have the variable, codegen'ing the assignment is straightforward:
|
|
we emit the RHS of the assignment, create a store, and return the computed
|
|
value. Returning a value allows for chained assignments like "X = (Y = Z)".</p>
|
|
|
|
<p>Now that we have an assignment operator, we can mutate loop variables and
|
|
arguments. For example, we can now run code like this:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
# Function to print a double.
|
|
extern printd(x);
|
|
|
|
# Define ':' for sequencing: as a low-precedence operator that ignores operands
|
|
# and just returns the RHS.
|
|
def binary : 1 (x y) y;
|
|
|
|
def test(x)
|
|
printd(x) :
|
|
x = 4 :
|
|
printd(x);
|
|
|
|
test(123);
|
|
</pre>
|
|
</div>
|
|
|
|
<p>When run, this example prints "123" and then "4", showing that we did
|
|
actually mutate the value! Okay, we have now officially implemented our goal:
|
|
getting this to work requires SSA construction in the general case. However,
|
|
to be really useful, we want the ability to define our own local variables, lets
|
|
add this next!
|
|
</p>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section"><a name="localvars">User-defined Local
|
|
Variables</a></div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>Adding var/in is just like any other other extensions we made to
|
|
Kaleidoscope: we extend the lexer, the parser, the AST and the code generator.
|
|
The first step for adding our new 'var/in' construct is to extend the lexer.
|
|
As before, this is pretty trivial, the code looks like this:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
enum Token {
|
|
...
|
|
<b>// var definition
|
|
tok_var = -13</b>
|
|
...
|
|
}
|
|
...
|
|
static int gettok() {
|
|
...
|
|
if (IdentifierStr == "in") return tok_in;
|
|
if (IdentifierStr == "binary") return tok_binary;
|
|
if (IdentifierStr == "unary") return tok_unary;
|
|
<b>if (IdentifierStr == "var") return tok_var;</b>
|
|
return tok_identifier;
|
|
...
|
|
</pre>
|
|
</div>
|
|
|
|
<p>The next step is to define the AST node that we will construct. For var/in,
|
|
it looks like this:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
/// VarExprAST - Expression class for var/in
|
|
class VarExprAST : public ExprAST {
|
|
std::vector<std::pair<std::string, ExprAST*> > VarNames;
|
|
ExprAST *Body;
|
|
public:
|
|
VarExprAST(const std::vector<std::pair<std::string, ExprAST*> > &varnames,
|
|
ExprAST *body)
|
|
: VarNames(varnames), Body(body) {}
|
|
|
|
virtual Value *Codegen();
|
|
};
|
|
</pre>
|
|
</div>
|
|
|
|
<p>var/in allows a list of names to be defined all at once, and each name can
|
|
optionally have an initializer value. As such, we capture this information in
|
|
the VarNames vector. Also, var/in has a body, this body is allowed to access
|
|
the variables defined by the var/in.</p>
|
|
|
|
<p>With this in place, we can define the parser pieces. The first thing we do is add
|
|
it as a primary expression:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
/// primary
|
|
/// ::= identifierexpr
|
|
/// ::= numberexpr
|
|
/// ::= parenexpr
|
|
/// ::= ifexpr
|
|
/// ::= forexpr
|
|
<b>/// ::= varexpr</b>
|
|
static ExprAST *ParsePrimary() {
|
|
switch (CurTok) {
|
|
default: return Error("unknown token when expecting an expression");
|
|
case tok_identifier: return ParseIdentifierExpr();
|
|
case tok_number: return ParseNumberExpr();
|
|
case '(': return ParseParenExpr();
|
|
case tok_if: return ParseIfExpr();
|
|
case tok_for: return ParseForExpr();
|
|
<b>case tok_var: return ParseVarExpr();</b>
|
|
}
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Next we define ParseVarExpr:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
/// varexpr ::= 'var' identifier ('=' expression)?
|
|
// (',' identifier ('=' expression)?)* 'in' expression
|
|
static ExprAST *ParseVarExpr() {
|
|
getNextToken(); // eat the var.
|
|
|
|
std::vector<std::pair<std::string, ExprAST*> > VarNames;
|
|
|
|
// At least one variable name is required.
|
|
if (CurTok != tok_identifier)
|
|
return Error("expected identifier after var");
|
|
</pre>
|
|
</div>
|
|
|
|
<p>The first part of this code parses the list of identifier/expr pairs into the
|
|
local <tt>VarNames</tt> vector.
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
while (1) {
|
|
std::string Name = IdentifierStr;
|
|
getNextToken(); // eat identifier.
|
|
|
|
// Read the optional initializer.
|
|
ExprAST *Init = 0;
|
|
if (CurTok == '=') {
|
|
getNextToken(); // eat the '='.
|
|
|
|
Init = ParseExpression();
|
|
if (Init == 0) return 0;
|
|
}
|
|
|
|
VarNames.push_back(std::make_pair(Name, Init));
|
|
|
|
// End of var list, exit loop.
|
|
if (CurTok != ',') break;
|
|
getNextToken(); // eat the ','.
|
|
|
|
if (CurTok != tok_identifier)
|
|
return Error("expected identifier list after var");
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Once all the variables are parsed, we then parse the body and create the
|
|
AST node:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
// At this point, we have to have 'in'.
|
|
if (CurTok != tok_in)
|
|
return Error("expected 'in' keyword after 'var'");
|
|
getNextToken(); // eat 'in'.
|
|
|
|
ExprAST *Body = ParseExpression();
|
|
if (Body == 0) return 0;
|
|
|
|
return new VarExprAST(VarNames, Body);
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Now that we can parse and represent the code, we need to support emission of
|
|
LLVM IR for it. This code starts out with:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
Value *VarExprAST::Codegen() {
|
|
std::vector<AllocaInst *> OldBindings;
|
|
|
|
Function *TheFunction = Builder.GetInsertBlock()->getParent();
|
|
|
|
// Register all variables and emit their initializer.
|
|
for (unsigned i = 0, e = VarNames.size(); i != e; ++i) {
|
|
const std::string &VarName = VarNames[i].first;
|
|
ExprAST *Init = VarNames[i].second;
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Basically it loops over all the variables, installing them one at a time.
|
|
For each variable we put into the symbol table, we remember the previous value
|
|
that we replace in OldBindings.</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
// Emit the initializer before adding the variable to scope, this prevents
|
|
// the initializer from referencing the variable itself, and permits stuff
|
|
// like this:
|
|
// var a = 1 in
|
|
// var a = a in ... # refers to outer 'a'.
|
|
Value *InitVal;
|
|
if (Init) {
|
|
InitVal = Init->Codegen();
|
|
if (InitVal == 0) return 0;
|
|
} else { // If not specified, use 0.0.
|
|
InitVal = ConstantFP::get(Type::DoubleTy, APFloat(0.0));
|
|
}
|
|
|
|
AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
|
|
Builder.CreateStore(InitVal, Alloca);
|
|
|
|
// Remember the old variable binding so that we can restore the binding when
|
|
// we unrecurse.
|
|
OldBindings.push_back(NamedValues[VarName]);
|
|
|
|
// Remember this binding.
|
|
NamedValues[VarName] = Alloca;
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>There are more comments here than code. The basic idea is that we emit the
|
|
initializer, create the alloca, then update the symbol table to point to it.
|
|
Once all the variables are installed in the symbol table, we evaluate the body
|
|
of the var/in expression:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
// Codegen the body, now that all vars are in scope.
|
|
Value *BodyVal = Body->Codegen();
|
|
if (BodyVal == 0) return 0;
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Finally, before returning, we restore the previous variable bindings:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
// Pop all our variables from scope.
|
|
for (unsigned i = 0, e = VarNames.size(); i != e; ++i)
|
|
NamedValues[VarNames[i].first] = OldBindings[i];
|
|
|
|
// Return the body computation.
|
|
return BodyVal;
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<p>The end result of all of this is that we get properly scoped variable
|
|
definitions, and we even (trivially) allow mutation of them :).</p>
|
|
|
|
<p>With this, we completed what we set out to do. Our nice iterative fib
|
|
example from the intro compiles and runs just fine. The mem2reg pass optimizes
|
|
all of our stack variables into SSA registers, inserting PHI nodes where needed,
|
|
and our front-end remains simple: no "iterated dominance frontier" computation
|
|
anywhere in sight.</p>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section"><a name="code">Full Code Listing</a></div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>
|
|
Here is the complete code listing for our running example, enhanced with mutable
|
|
variables and var/in support. To build this example, use:
|
|
</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
# Compile
|
|
g++ -g toy.cpp `llvm-config --cppflags --ldflags --libs core jit native` -O3 -o toy
|
|
# Run
|
|
./toy
|
|
</pre>
|
|
</div>
|
|
|
|
<p>Here is the code:</p>
|
|
|
|
<div class="doc_code">
|
|
<pre>
|
|
#include "llvm/DerivedTypes.h"
|
|
#include "llvm/ExecutionEngine/ExecutionEngine.h"
|
|
#include "llvm/Module.h"
|
|
#include "llvm/ModuleProvider.h"
|
|
#include "llvm/PassManager.h"
|
|
#include "llvm/Analysis/Verifier.h"
|
|
#include "llvm/Target/TargetData.h"
|
|
#include "llvm/Transforms/Scalar.h"
|
|
#include "llvm/Support/LLVMBuilder.h"
|
|
#include <cstdio>
|
|
#include <string>
|
|
#include <map>
|
|
#include <vector>
|
|
using namespace llvm;
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// Lexer
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
// The lexer returns tokens [0-255] if it is an unknown character, otherwise one
|
|
// of these for known things.
|
|
enum Token {
|
|
tok_eof = -1,
|
|
|
|
// commands
|
|
tok_def = -2, tok_extern = -3,
|
|
|
|
// primary
|
|
tok_identifier = -4, tok_number = -5,
|
|
|
|
// control
|
|
tok_if = -6, tok_then = -7, tok_else = -8,
|
|
tok_for = -9, tok_in = -10,
|
|
|
|
// operators
|
|
tok_binary = -11, tok_unary = -12,
|
|
|
|
// var definition
|
|
tok_var = -13
|
|
};
|
|
|
|
static std::string IdentifierStr; // Filled in if tok_identifier
|
|
static double NumVal; // Filled in if tok_number
|
|
|
|
/// gettok - Return the next token from standard input.
|
|
static int gettok() {
|
|
static int LastChar = ' ';
|
|
|
|
// Skip any whitespace.
|
|
while (isspace(LastChar))
|
|
LastChar = getchar();
|
|
|
|
if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
|
|
IdentifierStr = LastChar;
|
|
while (isalnum((LastChar = getchar())))
|
|
IdentifierStr += LastChar;
|
|
|
|
if (IdentifierStr == "def") return tok_def;
|
|
if (IdentifierStr == "extern") return tok_extern;
|
|
if (IdentifierStr == "if") return tok_if;
|
|
if (IdentifierStr == "then") return tok_then;
|
|
if (IdentifierStr == "else") return tok_else;
|
|
if (IdentifierStr == "for") return tok_for;
|
|
if (IdentifierStr == "in") return tok_in;
|
|
if (IdentifierStr == "binary") return tok_binary;
|
|
if (IdentifierStr == "unary") return tok_unary;
|
|
if (IdentifierStr == "var") return tok_var;
|
|
return tok_identifier;
|
|
}
|
|
|
|
if (isdigit(LastChar) || LastChar == '.') { // Number: [0-9.]+
|
|
std::string NumStr;
|
|
do {
|
|
NumStr += LastChar;
|
|
LastChar = getchar();
|
|
} while (isdigit(LastChar) || LastChar == '.');
|
|
|
|
NumVal = strtod(NumStr.c_str(), 0);
|
|
return tok_number;
|
|
}
|
|
|
|
if (LastChar == '#') {
|
|
// Comment until end of line.
|
|
do LastChar = getchar();
|
|
while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
|
|
|
|
if (LastChar != EOF)
|
|
return gettok();
|
|
}
|
|
|
|
// Check for end of file. Don't eat the EOF.
|
|
if (LastChar == EOF)
|
|
return tok_eof;
|
|
|
|
// Otherwise, just return the character as its ascii value.
|
|
int ThisChar = LastChar;
|
|
LastChar = getchar();
|
|
return ThisChar;
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// Abstract Syntax Tree (aka Parse Tree)
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
/// ExprAST - Base class for all expression nodes.
|
|
class ExprAST {
|
|
public:
|
|
virtual ~ExprAST() {}
|
|
virtual Value *Codegen() = 0;
|
|
};
|
|
|
|
/// NumberExprAST - Expression class for numeric literals like "1.0".
|
|
class NumberExprAST : public ExprAST {
|
|
double Val;
|
|
public:
|
|
NumberExprAST(double val) : Val(val) {}
|
|
virtual Value *Codegen();
|
|
};
|
|
|
|
/// VariableExprAST - Expression class for referencing a variable, like "a".
|
|
class VariableExprAST : public ExprAST {
|
|
std::string Name;
|
|
public:
|
|
VariableExprAST(const std::string &name) : Name(name) {}
|
|
const std::string &getName() const { return Name; }
|
|
virtual Value *Codegen();
|
|
};
|
|
|
|
/// UnaryExprAST - Expression class for a unary operator.
|
|
class UnaryExprAST : public ExprAST {
|
|
char Opcode;
|
|
ExprAST *Operand;
|
|
public:
|
|
UnaryExprAST(char opcode, ExprAST *operand)
|
|
: Opcode(opcode), Operand(operand) {}
|
|
virtual Value *Codegen();
|
|
};
|
|
|
|
/// BinaryExprAST - Expression class for a binary operator.
|
|
class BinaryExprAST : public ExprAST {
|
|
char Op;
|
|
ExprAST *LHS, *RHS;
|
|
public:
|
|
BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
|
|
: Op(op), LHS(lhs), RHS(rhs) {}
|
|
virtual Value *Codegen();
|
|
};
|
|
|
|
/// CallExprAST - Expression class for function calls.
|
|
class CallExprAST : public ExprAST {
|
|
std::string Callee;
|
|
std::vector<ExprAST*> Args;
|
|
public:
|
|
CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
|
|
: Callee(callee), Args(args) {}
|
|
virtual Value *Codegen();
|
|
};
|
|
|
|
/// IfExprAST - Expression class for if/then/else.
|
|
class IfExprAST : public ExprAST {
|
|
ExprAST *Cond, *Then, *Else;
|
|
public:
|
|
IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
|
|
: Cond(cond), Then(then), Else(_else) {}
|
|
virtual Value *Codegen();
|
|
};
|
|
|
|
/// ForExprAST - Expression class for for/in.
|
|
class ForExprAST : public ExprAST {
|
|
std::string VarName;
|
|
ExprAST *Start, *End, *Step, *Body;
|
|
public:
|
|
ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
|
|
ExprAST *step, ExprAST *body)
|
|
: VarName(varname), Start(start), End(end), Step(step), Body(body) {}
|
|
virtual Value *Codegen();
|
|
};
|
|
|
|
/// VarExprAST - Expression class for var/in
|
|
class VarExprAST : public ExprAST {
|
|
std::vector<std::pair<std::string, ExprAST*> > VarNames;
|
|
ExprAST *Body;
|
|
public:
|
|
VarExprAST(const std::vector<std::pair<std::string, ExprAST*> > &varnames,
|
|
ExprAST *body)
|
|
: VarNames(varnames), Body(body) {}
|
|
|
|
virtual Value *Codegen();
|
|
};
|
|
|
|
/// PrototypeAST - This class represents the "prototype" for a function,
|
|
/// which captures its argument names as well as if it is an operator.
|
|
class PrototypeAST {
|
|
std::string Name;
|
|
std::vector<std::string> Args;
|
|
bool isOperator;
|
|
unsigned Precedence; // Precedence if a binary op.
|
|
public:
|
|
PrototypeAST(const std::string &name, const std::vector<std::string> &args,
|
|
bool isoperator = false, unsigned prec = 0)
|
|
: Name(name), Args(args), isOperator(isoperator), Precedence(prec) {}
|
|
|
|
bool isUnaryOp() const { return isOperator && Args.size() == 1; }
|
|
bool isBinaryOp() const { return isOperator && Args.size() == 2; }
|
|
|
|
char getOperatorName() const {
|
|
assert(isUnaryOp() || isBinaryOp());
|
|
return Name[Name.size()-1];
|
|
}
|
|
|
|
unsigned getBinaryPrecedence() const { return Precedence; }
|
|
|
|
Function *Codegen();
|
|
|
|
void CreateArgumentAllocas(Function *F);
|
|
};
|
|
|
|
/// FunctionAST - This class represents a function definition itself.
|
|
class FunctionAST {
|
|
PrototypeAST *Proto;
|
|
ExprAST *Body;
|
|
public:
|
|
FunctionAST(PrototypeAST *proto, ExprAST *body)
|
|
: Proto(proto), Body(body) {}
|
|
|
|
Function *Codegen();
|
|
};
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// Parser
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
/// CurTok/getNextToken - Provide a simple token buffer. CurTok is the current
|
|
/// token the parser it looking at. getNextToken reads another token from the
|
|
/// lexer and updates CurTok with its results.
|
|
static int CurTok;
|
|
static int getNextToken() {
|
|
return CurTok = gettok();
|
|
}
|
|
|
|
/// BinopPrecedence - This holds the precedence for each binary operator that is
|
|
/// defined.
|
|
static std::map<char, int> BinopPrecedence;
|
|
|
|
/// GetTokPrecedence - Get the precedence of the pending binary operator token.
|
|
static int GetTokPrecedence() {
|
|
if (!isascii(CurTok))
|
|
return -1;
|
|
|
|
// Make sure it's a declared binop.
|
|
int TokPrec = BinopPrecedence[CurTok];
|
|
if (TokPrec <= 0) return -1;
|
|
return TokPrec;
|
|
}
|
|
|
|
/// Error* - These are little helper functions for error handling.
|
|
ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
|
|
PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
|
|
FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
|
|
|
|
static ExprAST *ParseExpression();
|
|
|
|
/// identifierexpr
|
|
/// ::= identifier
|
|
/// ::= identifier '(' expression* ')'
|
|
static ExprAST *ParseIdentifierExpr() {
|
|
std::string IdName = IdentifierStr;
|
|
|
|
getNextToken(); // eat identifier.
|
|
|
|
if (CurTok != '(') // Simple variable ref.
|
|
return new VariableExprAST(IdName);
|
|
|
|
// Call.
|
|
getNextToken(); // eat (
|
|
std::vector<ExprAST*> Args;
|
|
if (CurTok != ')') {
|
|
while (1) {
|
|
ExprAST *Arg = ParseExpression();
|
|
if (!Arg) return 0;
|
|
Args.push_back(Arg);
|
|
|
|
if (CurTok == ')') break;
|
|
|
|
if (CurTok != ',')
|
|
return Error("Expected ')'");
|
|
getNextToken();
|
|
}
|
|
}
|
|
|
|
// Eat the ')'.
|
|
getNextToken();
|
|
|
|
return new CallExprAST(IdName, Args);
|
|
}
|
|
|
|
/// numberexpr ::= number
|
|
static ExprAST *ParseNumberExpr() {
|
|
ExprAST *Result = new NumberExprAST(NumVal);
|
|
getNextToken(); // consume the number
|
|
return Result;
|
|
}
|
|
|
|
/// parenexpr ::= '(' expression ')'
|
|
static ExprAST *ParseParenExpr() {
|
|
getNextToken(); // eat (.
|
|
ExprAST *V = ParseExpression();
|
|
if (!V) return 0;
|
|
|
|
if (CurTok != ')')
|
|
return Error("expected ')'");
|
|
getNextToken(); // eat ).
|
|
return V;
|
|
}
|
|
|
|
/// ifexpr ::= 'if' expression 'then' expression 'else' expression
|
|
static ExprAST *ParseIfExpr() {
|
|
getNextToken(); // eat the if.
|
|
|
|
// condition.
|
|
ExprAST *Cond = ParseExpression();
|
|
if (!Cond) return 0;
|
|
|
|
if (CurTok != tok_then)
|
|
return Error("expected then");
|
|
getNextToken(); // eat the then
|
|
|
|
ExprAST *Then = ParseExpression();
|
|
if (Then == 0) return 0;
|
|
|
|
if (CurTok != tok_else)
|
|
return Error("expected else");
|
|
|
|
getNextToken();
|
|
|
|
ExprAST *Else = ParseExpression();
|
|
if (!Else) return 0;
|
|
|
|
return new IfExprAST(Cond, Then, Else);
|
|
}
|
|
|
|
/// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
|
|
static ExprAST *ParseForExpr() {
|
|
getNextToken(); // eat the for.
|
|
|
|
if (CurTok != tok_identifier)
|
|
return Error("expected identifier after for");
|
|
|
|
std::string IdName = IdentifierStr;
|
|
getNextToken(); // eat identifier.
|
|
|
|
if (CurTok != '=')
|
|
return Error("expected '=' after for");
|
|
getNextToken(); // eat '='.
|
|
|
|
|
|
ExprAST *Start = ParseExpression();
|
|
if (Start == 0) return 0;
|
|
if (CurTok != ',')
|
|
return Error("expected ',' after for start value");
|
|
getNextToken();
|
|
|
|
ExprAST *End = ParseExpression();
|
|
if (End == 0) return 0;
|
|
|
|
// The step value is optional.
|
|
ExprAST *Step = 0;
|
|
if (CurTok == ',') {
|
|
getNextToken();
|
|
Step = ParseExpression();
|
|
if (Step == 0) return 0;
|
|
}
|
|
|
|
if (CurTok != tok_in)
|
|
return Error("expected 'in' after for");
|
|
getNextToken(); // eat 'in'.
|
|
|
|
ExprAST *Body = ParseExpression();
|
|
if (Body == 0) return 0;
|
|
|
|
return new ForExprAST(IdName, Start, End, Step, Body);
|
|
}
|
|
|
|
/// varexpr ::= 'var' identifier ('=' expression)?
|
|
// (',' identifier ('=' expression)?)* 'in' expression
|
|
static ExprAST *ParseVarExpr() {
|
|
getNextToken(); // eat the var.
|
|
|
|
std::vector<std::pair<std::string, ExprAST*> > VarNames;
|
|
|
|
// At least one variable name is required.
|
|
if (CurTok != tok_identifier)
|
|
return Error("expected identifier after var");
|
|
|
|
while (1) {
|
|
std::string Name = IdentifierStr;
|
|
getNextToken(); // eat identifier.
|
|
|
|
// Read the optional initializer.
|
|
ExprAST *Init = 0;
|
|
if (CurTok == '=') {
|
|
getNextToken(); // eat the '='.
|
|
|
|
Init = ParseExpression();
|
|
if (Init == 0) return 0;
|
|
}
|
|
|
|
VarNames.push_back(std::make_pair(Name, Init));
|
|
|
|
// End of var list, exit loop.
|
|
if (CurTok != ',') break;
|
|
getNextToken(); // eat the ','.
|
|
|
|
if (CurTok != tok_identifier)
|
|
return Error("expected identifier list after var");
|
|
}
|
|
|
|
// At this point, we have to have 'in'.
|
|
if (CurTok != tok_in)
|
|
return Error("expected 'in' keyword after 'var'");
|
|
getNextToken(); // eat 'in'.
|
|
|
|
ExprAST *Body = ParseExpression();
|
|
if (Body == 0) return 0;
|
|
|
|
return new VarExprAST(VarNames, Body);
|
|
}
|
|
|
|
|
|
/// primary
|
|
/// ::= identifierexpr
|
|
/// ::= numberexpr
|
|
/// ::= parenexpr
|
|
/// ::= ifexpr
|
|
/// ::= forexpr
|
|
/// ::= varexpr
|
|
static ExprAST *ParsePrimary() {
|
|
switch (CurTok) {
|
|
default: return Error("unknown token when expecting an expression");
|
|
case tok_identifier: return ParseIdentifierExpr();
|
|
case tok_number: return ParseNumberExpr();
|
|
case '(': return ParseParenExpr();
|
|
case tok_if: return ParseIfExpr();
|
|
case tok_for: return ParseForExpr();
|
|
case tok_var: return ParseVarExpr();
|
|
}
|
|
}
|
|
|
|
/// unary
|
|
/// ::= primary
|
|
/// ::= '!' unary
|
|
static ExprAST *ParseUnary() {
|
|
// If the current token is not an operator, it must be a primary expr.
|
|
if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
|
|
return ParsePrimary();
|
|
|
|
// If this is a unary operator, read it.
|
|
int Opc = CurTok;
|
|
getNextToken();
|
|
if (ExprAST *Operand = ParseUnary())
|
|
return new UnaryExprAST(Opc, Operand);
|
|
return 0;
|
|
}
|
|
|
|
/// binoprhs
|
|
/// ::= ('+' unary)*
|
|
static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
|
|
// If this is a binop, find its precedence.
|
|
while (1) {
|
|
int TokPrec = GetTokPrecedence();
|
|
|
|
// If this is a binop that binds at least as tightly as the current binop,
|
|
// consume it, otherwise we are done.
|
|
if (TokPrec < ExprPrec)
|
|
return LHS;
|
|
|
|
// Okay, we know this is a binop.
|
|
int BinOp = CurTok;
|
|
getNextToken(); // eat binop
|
|
|
|
// Parse the unary expression after the binary operator.
|
|
ExprAST *RHS = ParseUnary();
|
|
if (!RHS) return 0;
|
|
|
|
// If BinOp binds less tightly with RHS than the operator after RHS, let
|
|
// the pending operator take RHS as its LHS.
|
|
int NextPrec = GetTokPrecedence();
|
|
if (TokPrec < NextPrec) {
|
|
RHS = ParseBinOpRHS(TokPrec+1, RHS);
|
|
if (RHS == 0) return 0;
|
|
}
|
|
|
|
// Merge LHS/RHS.
|
|
LHS = new BinaryExprAST(BinOp, LHS, RHS);
|
|
}
|
|
}
|
|
|
|
/// expression
|
|
/// ::= unary binoprhs
|
|
///
|
|
static ExprAST *ParseExpression() {
|
|
ExprAST *LHS = ParseUnary();
|
|
if (!LHS) return 0;
|
|
|
|
return ParseBinOpRHS(0, LHS);
|
|
}
|
|
|
|
/// prototype
|
|
/// ::= id '(' id* ')'
|
|
/// ::= binary LETTER number? (id, id)
|
|
/// ::= unary LETTER (id)
|
|
static PrototypeAST *ParsePrototype() {
|
|
std::string FnName;
|
|
|
|
int Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
|
|
unsigned BinaryPrecedence = 30;
|
|
|
|
switch (CurTok) {
|
|
default:
|
|
return ErrorP("Expected function name in prototype");
|
|
case tok_identifier:
|
|
FnName = IdentifierStr;
|
|
Kind = 0;
|
|
getNextToken();
|
|
break;
|
|
case tok_unary:
|
|
getNextToken();
|
|
if (!isascii(CurTok))
|
|
return ErrorP("Expected unary operator");
|
|
FnName = "unary";
|
|
FnName += (char)CurTok;
|
|
Kind = 1;
|
|
getNextToken();
|
|
break;
|
|
case tok_binary:
|
|
getNextToken();
|
|
if (!isascii(CurTok))
|
|
return ErrorP("Expected binary operator");
|
|
FnName = "binary";
|
|
FnName += (char)CurTok;
|
|
Kind = 2;
|
|
getNextToken();
|
|
|
|
// Read the precedence if present.
|
|
if (CurTok == tok_number) {
|
|
if (NumVal < 1 || NumVal > 100)
|
|
return ErrorP("Invalid precedecnce: must be 1..100");
|
|
BinaryPrecedence = (unsigned)NumVal;
|
|
getNextToken();
|
|
}
|
|
break;
|
|
}
|
|
|
|
if (CurTok != '(')
|
|
return ErrorP("Expected '(' in prototype");
|
|
|
|
std::vector<std::string> ArgNames;
|
|
while (getNextToken() == tok_identifier)
|
|
ArgNames.push_back(IdentifierStr);
|
|
if (CurTok != ')')
|
|
return ErrorP("Expected ')' in prototype");
|
|
|
|
// success.
|
|
getNextToken(); // eat ')'.
|
|
|
|
// Verify right number of names for operator.
|
|
if (Kind && ArgNames.size() != Kind)
|
|
return ErrorP("Invalid number of operands for operator");
|
|
|
|
return new PrototypeAST(FnName, ArgNames, Kind != 0, BinaryPrecedence);
|
|
}
|
|
|
|
/// definition ::= 'def' prototype expression
|
|
static FunctionAST *ParseDefinition() {
|
|
getNextToken(); // eat def.
|
|
PrototypeAST *Proto = ParsePrototype();
|
|
if (Proto == 0) return 0;
|
|
|
|
if (ExprAST *E = ParseExpression())
|
|
return new FunctionAST(Proto, E);
|
|
return 0;
|
|
}
|
|
|
|
/// toplevelexpr ::= expression
|
|
static FunctionAST *ParseTopLevelExpr() {
|
|
if (ExprAST *E = ParseExpression()) {
|
|
// Make an anonymous proto.
|
|
PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
|
|
return new FunctionAST(Proto, E);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/// external ::= 'extern' prototype
|
|
static PrototypeAST *ParseExtern() {
|
|
getNextToken(); // eat extern.
|
|
return ParsePrototype();
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// Code Generation
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
static Module *TheModule;
|
|
static LLVMFoldingBuilder Builder;
|
|
static std::map<std::string, AllocaInst*> NamedValues;
|
|
static FunctionPassManager *TheFPM;
|
|
|
|
Value *ErrorV(const char *Str) { Error(Str); return 0; }
|
|
|
|
/// CreateEntryBlockAlloca - Create an alloca instruction in the entry block of
|
|
/// the function. This is used for mutable variables etc.
|
|
static AllocaInst *CreateEntryBlockAlloca(Function *TheFunction,
|
|
const std::string &VarName) {
|
|
LLVMBuilder TmpB(&TheFunction->getEntryBlock(),
|
|
TheFunction->getEntryBlock().begin());
|
|
return TmpB.CreateAlloca(Type::DoubleTy, 0, VarName.c_str());
|
|
}
|
|
|
|
|
|
Value *NumberExprAST::Codegen() {
|
|
return ConstantFP::get(Type::DoubleTy, APFloat(Val));
|
|
}
|
|
|
|
Value *VariableExprAST::Codegen() {
|
|
// Look this variable up in the function.
|
|
Value *V = NamedValues[Name];
|
|
if (V == 0) return ErrorV("Unknown variable name");
|
|
|
|
// Load the value.
|
|
return Builder.CreateLoad(V, Name.c_str());
|
|
}
|
|
|
|
Value *UnaryExprAST::Codegen() {
|
|
Value *OperandV = Operand->Codegen();
|
|
if (OperandV == 0) return 0;
|
|
|
|
Function *F = TheModule->getFunction(std::string("unary")+Opcode);
|
|
if (F == 0)
|
|
return ErrorV("Unknown unary operator");
|
|
|
|
return Builder.CreateCall(F, OperandV, "unop");
|
|
}
|
|
|
|
|
|
Value *BinaryExprAST::Codegen() {
|
|
// Special case '=' because we don't want to emit the LHS as an expression.
|
|
if (Op == '=') {
|
|
// Assignment requires the LHS to be an identifier.
|
|
VariableExprAST *LHSE = dynamic_cast<VariableExprAST*>(LHS);
|
|
if (!LHSE)
|
|
return ErrorV("destination of '=' must be a variable");
|
|
// Codegen the RHS.
|
|
Value *Val = RHS->Codegen();
|
|
if (Val == 0) return 0;
|
|
|
|
// Look up the name.
|
|
Value *Variable = NamedValues[LHSE->getName()];
|
|
if (Variable == 0) return ErrorV("Unknown variable name");
|
|
|
|
Builder.CreateStore(Val, Variable);
|
|
return Val;
|
|
}
|
|
|
|
|
|
Value *L = LHS->Codegen();
|
|
Value *R = RHS->Codegen();
|
|
if (L == 0 || R == 0) return 0;
|
|
|
|
switch (Op) {
|
|
case '+': return Builder.CreateAdd(L, R, "addtmp");
|
|
case '-': return Builder.CreateSub(L, R, "subtmp");
|
|
case '*': return Builder.CreateMul(L, R, "multmp");
|
|
case '<':
|
|
L = Builder.CreateFCmpULT(L, R, "cmptmp");
|
|
// Convert bool 0/1 to double 0.0 or 1.0
|
|
return Builder.CreateUIToFP(L, Type::DoubleTy, "booltmp");
|
|
default: break;
|
|
}
|
|
|
|
// If it wasn't a builtin binary operator, it must be a user defined one. Emit
|
|
// a call to it.
|
|
Function *F = TheModule->getFunction(std::string("binary")+Op);
|
|
assert(F && "binary operator not found!");
|
|
|
|
Value *Ops[] = { L, R };
|
|
return Builder.CreateCall(F, Ops, Ops+2, "binop");
|
|
}
|
|
|
|
Value *CallExprAST::Codegen() {
|
|
// Look up the name in the global module table.
|
|
Function *CalleeF = TheModule->getFunction(Callee);
|
|
if (CalleeF == 0)
|
|
return ErrorV("Unknown function referenced");
|
|
|
|
// If argument mismatch error.
|
|
if (CalleeF->arg_size() != Args.size())
|
|
return ErrorV("Incorrect # arguments passed");
|
|
|
|
std::vector<Value*> ArgsV;
|
|
for (unsigned i = 0, e = Args.size(); i != e; ++i) {
|
|
ArgsV.push_back(Args[i]->Codegen());
|
|
if (ArgsV.back() == 0) return 0;
|
|
}
|
|
|
|
return Builder.CreateCall(CalleeF, ArgsV.begin(), ArgsV.end(), "calltmp");
|
|
}
|
|
|
|
Value *IfExprAST::Codegen() {
|
|
Value *CondV = Cond->Codegen();
|
|
if (CondV == 0) return 0;
|
|
|
|
// Convert condition to a bool by comparing equal to 0.0.
|
|
CondV = Builder.CreateFCmpONE(CondV,
|
|
ConstantFP::get(Type::DoubleTy, APFloat(0.0)),
|
|
"ifcond");
|
|
|
|
Function *TheFunction = Builder.GetInsertBlock()->getParent();
|
|
|
|
// Create blocks for the then and else cases. Insert the 'then' block at the
|
|
// end of the function.
|
|
BasicBlock *ThenBB = new BasicBlock("then", TheFunction);
|
|
BasicBlock *ElseBB = new BasicBlock("else");
|
|
BasicBlock *MergeBB = new BasicBlock("ifcont");
|
|
|
|
Builder.CreateCondBr(CondV, ThenBB, ElseBB);
|
|
|
|
// Emit then value.
|
|
Builder.SetInsertPoint(ThenBB);
|
|
|
|
Value *ThenV = Then->Codegen();
|
|
if (ThenV == 0) return 0;
|
|
|
|
Builder.CreateBr(MergeBB);
|
|
// Codegen of 'Then' can change the current block, update ThenBB for the PHI.
|
|
ThenBB = Builder.GetInsertBlock();
|
|
|
|
// Emit else block.
|
|
TheFunction->getBasicBlockList().push_back(ElseBB);
|
|
Builder.SetInsertPoint(ElseBB);
|
|
|
|
Value *ElseV = Else->Codegen();
|
|
if (ElseV == 0) return 0;
|
|
|
|
Builder.CreateBr(MergeBB);
|
|
// Codegen of 'Else' can change the current block, update ElseBB for the PHI.
|
|
ElseBB = Builder.GetInsertBlock();
|
|
|
|
// Emit merge block.
|
|
TheFunction->getBasicBlockList().push_back(MergeBB);
|
|
Builder.SetInsertPoint(MergeBB);
|
|
PHINode *PN = Builder.CreatePHI(Type::DoubleTy, "iftmp");
|
|
|
|
PN->addIncoming(ThenV, ThenBB);
|
|
PN->addIncoming(ElseV, ElseBB);
|
|
return PN;
|
|
}
|
|
|
|
Value *ForExprAST::Codegen() {
|
|
// Output this as:
|
|
// var = alloca double
|
|
// ...
|
|
// start = startexpr
|
|
// store start -> var
|
|
// goto loop
|
|
// loop:
|
|
// ...
|
|
// bodyexpr
|
|
// ...
|
|
// loopend:
|
|
// step = stepexpr
|
|
// endcond = endexpr
|
|
//
|
|
// curvar = load var
|
|
// nextvar = curvar + step
|
|
// store nextvar -> var
|
|
// br endcond, loop, endloop
|
|
// outloop:
|
|
|
|
Function *TheFunction = Builder.GetInsertBlock()->getParent();
|
|
|
|
// Create an alloca for the variable in the entry block.
|
|
AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
|
|
|
|
// Emit the start code first, without 'variable' in scope.
|
|
Value *StartVal = Start->Codegen();
|
|
if (StartVal == 0) return 0;
|
|
|
|
// Store the value into the alloca.
|
|
Builder.CreateStore(StartVal, Alloca);
|
|
|
|
// Make the new basic block for the loop header, inserting after current
|
|
// block.
|
|
BasicBlock *PreheaderBB = Builder.GetInsertBlock();
|
|
BasicBlock *LoopBB = new BasicBlock("loop", TheFunction);
|
|
|
|
// Insert an explicit fall through from the current block to the LoopBB.
|
|
Builder.CreateBr(LoopBB);
|
|
|
|
// Start insertion in LoopBB.
|
|
Builder.SetInsertPoint(LoopBB);
|
|
|
|
// Within the loop, the variable is defined equal to the PHI node. If it
|
|
// shadows an existing variable, we have to restore it, so save it now.
|
|
AllocaInst *OldVal = NamedValues[VarName];
|
|
NamedValues[VarName] = Alloca;
|
|
|
|
// Emit the body of the loop. This, like any other expr, can change the
|
|
// current BB. Note that we ignore the value computed by the body, but don't
|
|
// allow an error.
|
|
if (Body->Codegen() == 0)
|
|
return 0;
|
|
|
|
// Emit the step value.
|
|
Value *StepVal;
|
|
if (Step) {
|
|
StepVal = Step->Codegen();
|
|
if (StepVal == 0) return 0;
|
|
} else {
|
|
// If not specified, use 1.0.
|
|
StepVal = ConstantFP::get(Type::DoubleTy, APFloat(1.0));
|
|
}
|
|
|
|
// Compute the end condition.
|
|
Value *EndCond = End->Codegen();
|
|
if (EndCond == 0) return EndCond;
|
|
|
|
// Reload, increment, and restore the alloca. This handles the case where
|
|
// the body of the loop mutates the variable.
|
|
Value *CurVar = Builder.CreateLoad(Alloca, VarName.c_str());
|
|
Value *NextVar = Builder.CreateAdd(CurVar, StepVal, "nextvar");
|
|
Builder.CreateStore(NextVar, Alloca);
|
|
|
|
// Convert condition to a bool by comparing equal to 0.0.
|
|
EndCond = Builder.CreateFCmpONE(EndCond,
|
|
ConstantFP::get(Type::DoubleTy, APFloat(0.0)),
|
|
"loopcond");
|
|
|
|
// Create the "after loop" block and insert it.
|
|
BasicBlock *LoopEndBB = Builder.GetInsertBlock();
|
|
BasicBlock *AfterBB = new BasicBlock("afterloop", TheFunction);
|
|
|
|
// Insert the conditional branch into the end of LoopEndBB.
|
|
Builder.CreateCondBr(EndCond, LoopBB, AfterBB);
|
|
|
|
// Any new code will be inserted in AfterBB.
|
|
Builder.SetInsertPoint(AfterBB);
|
|
|
|
// Restore the unshadowed variable.
|
|
if (OldVal)
|
|
NamedValues[VarName] = OldVal;
|
|
else
|
|
NamedValues.erase(VarName);
|
|
|
|
|
|
// for expr always returns 0.0.
|
|
return Constant::getNullValue(Type::DoubleTy);
|
|
}
|
|
|
|
Value *VarExprAST::Codegen() {
|
|
std::vector<AllocaInst *> OldBindings;
|
|
|
|
Function *TheFunction = Builder.GetInsertBlock()->getParent();
|
|
|
|
// Register all variables and emit their initializer.
|
|
for (unsigned i = 0, e = VarNames.size(); i != e; ++i) {
|
|
const std::string &VarName = VarNames[i].first;
|
|
ExprAST *Init = VarNames[i].second;
|
|
|
|
// Emit the initializer before adding the variable to scope, this prevents
|
|
// the initializer from referencing the variable itself, and permits stuff
|
|
// like this:
|
|
// var a = 1 in
|
|
// var a = a in ... # refers to outer 'a'.
|
|
Value *InitVal;
|
|
if (Init) {
|
|
InitVal = Init->Codegen();
|
|
if (InitVal == 0) return 0;
|
|
} else { // If not specified, use 0.0.
|
|
InitVal = ConstantFP::get(Type::DoubleTy, APFloat(0.0));
|
|
}
|
|
|
|
AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
|
|
Builder.CreateStore(InitVal, Alloca);
|
|
|
|
// Remember the old variable binding so that we can restore the binding when
|
|
// we unrecurse.
|
|
OldBindings.push_back(NamedValues[VarName]);
|
|
|
|
// Remember this binding.
|
|
NamedValues[VarName] = Alloca;
|
|
}
|
|
|
|
// Codegen the body, now that all vars are in scope.
|
|
Value *BodyVal = Body->Codegen();
|
|
if (BodyVal == 0) return 0;
|
|
|
|
// Pop all our variables from scope.
|
|
for (unsigned i = 0, e = VarNames.size(); i != e; ++i)
|
|
NamedValues[VarNames[i].first] = OldBindings[i];
|
|
|
|
// Return the body computation.
|
|
return BodyVal;
|
|
}
|
|
|
|
|
|
Function *PrototypeAST::Codegen() {
|
|
// Make the function type: double(double,double) etc.
|
|
std::vector<const Type*> Doubles(Args.size(), Type::DoubleTy);
|
|
FunctionType *FT = FunctionType::get(Type::DoubleTy, Doubles, false);
|
|
|
|
Function *F = new Function(FT, Function::ExternalLinkage, Name, TheModule);
|
|
|
|
// If F conflicted, there was already something named 'Name'. If it has a
|
|
// body, don't allow redefinition or reextern.
|
|
if (F->getName() != Name) {
|
|
// Delete the one we just made and get the existing one.
|
|
F->eraseFromParent();
|
|
F = TheModule->getFunction(Name);
|
|
|
|
// If F already has a body, reject this.
|
|
if (!F->empty()) {
|
|
ErrorF("redefinition of function");
|
|
return 0;
|
|
}
|
|
|
|
// If F took a different number of args, reject.
|
|
if (F->arg_size() != Args.size()) {
|
|
ErrorF("redefinition of function with different # args");
|
|
return 0;
|
|
}
|
|
}
|
|
|
|
// Set names for all arguments.
|
|
unsigned Idx = 0;
|
|
for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
|
|
++AI, ++Idx)
|
|
AI->setName(Args[Idx]);
|
|
|
|
return F;
|
|
}
|
|
|
|
/// CreateArgumentAllocas - Create an alloca for each argument and register the
|
|
/// argument in the symbol table so that references to it will succeed.
|
|
void PrototypeAST::CreateArgumentAllocas(Function *F) {
|
|
Function::arg_iterator AI = F->arg_begin();
|
|
for (unsigned Idx = 0, e = Args.size(); Idx != e; ++Idx, ++AI) {
|
|
// Create an alloca for this variable.
|
|
AllocaInst *Alloca = CreateEntryBlockAlloca(F, Args[Idx]);
|
|
|
|
// Store the initial value into the alloca.
|
|
Builder.CreateStore(AI, Alloca);
|
|
|
|
// Add arguments to variable symbol table.
|
|
NamedValues[Args[Idx]] = Alloca;
|
|
}
|
|
}
|
|
|
|
|
|
Function *FunctionAST::Codegen() {
|
|
NamedValues.clear();
|
|
|
|
Function *TheFunction = Proto->Codegen();
|
|
if (TheFunction == 0)
|
|
return 0;
|
|
|
|
// If this is an operator, install it.
|
|
if (Proto->isBinaryOp())
|
|
BinopPrecedence[Proto->getOperatorName()] = Proto->getBinaryPrecedence();
|
|
|
|
// Create a new basic block to start insertion into.
|
|
BasicBlock *BB = new BasicBlock("entry", TheFunction);
|
|
Builder.SetInsertPoint(BB);
|
|
|
|
// Add all arguments to the symbol table and create their allocas.
|
|
Proto->CreateArgumentAllocas(TheFunction);
|
|
|
|
if (Value *RetVal = Body->Codegen()) {
|
|
// Finish off the function.
|
|
Builder.CreateRet(RetVal);
|
|
|
|
// Validate the generated code, checking for consistency.
|
|
verifyFunction(*TheFunction);
|
|
|
|
// Optimize the function.
|
|
TheFPM->run(*TheFunction);
|
|
|
|
return TheFunction;
|
|
}
|
|
|
|
// Error reading body, remove function.
|
|
TheFunction->eraseFromParent();
|
|
|
|
if (Proto->isBinaryOp())
|
|
BinopPrecedence.erase(Proto->getOperatorName());
|
|
return 0;
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// Top-Level parsing and JIT Driver
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
static ExecutionEngine *TheExecutionEngine;
|
|
|
|
static void HandleDefinition() {
|
|
if (FunctionAST *F = ParseDefinition()) {
|
|
if (Function *LF = F->Codegen()) {
|
|
fprintf(stderr, "Read function definition:");
|
|
LF->dump();
|
|
}
|
|
} else {
|
|
// Skip token for error recovery.
|
|
getNextToken();
|
|
}
|
|
}
|
|
|
|
static void HandleExtern() {
|
|
if (PrototypeAST *P = ParseExtern()) {
|
|
if (Function *F = P->Codegen()) {
|
|
fprintf(stderr, "Read extern: ");
|
|
F->dump();
|
|
}
|
|
} else {
|
|
// Skip token for error recovery.
|
|
getNextToken();
|
|
}
|
|
}
|
|
|
|
static void HandleTopLevelExpression() {
|
|
// Evaluate a top level expression into an anonymous function.
|
|
if (FunctionAST *F = ParseTopLevelExpr()) {
|
|
if (Function *LF = F->Codegen()) {
|
|
// JIT the function, returning a function pointer.
|
|
void *FPtr = TheExecutionEngine->getPointerToFunction(LF);
|
|
|
|
// Cast it to the right type (takes no arguments, returns a double) so we
|
|
// can call it as a native function.
|
|
double (*FP)() = (double (*)())FPtr;
|
|
fprintf(stderr, "Evaluated to %f\n", FP());
|
|
}
|
|
} else {
|
|
// Skip token for error recovery.
|
|
getNextToken();
|
|
}
|
|
}
|
|
|
|
/// top ::= definition | external | expression | ';'
|
|
static void MainLoop() {
|
|
while (1) {
|
|
fprintf(stderr, "ready> ");
|
|
switch (CurTok) {
|
|
case tok_eof: return;
|
|
case ';': getNextToken(); break; // ignore top level semicolons.
|
|
case tok_def: HandleDefinition(); break;
|
|
case tok_extern: HandleExtern(); break;
|
|
default: HandleTopLevelExpression(); break;
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// "Library" functions that can be "extern'd" from user code.
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
/// putchard - putchar that takes a double and returns 0.
|
|
extern "C"
|
|
double putchard(double X) {
|
|
putchar((char)X);
|
|
return 0;
|
|
}
|
|
|
|
/// printd - printf that takes a double prints it as "%f\n", returning 0.
|
|
extern "C"
|
|
double printd(double X) {
|
|
printf("%f\n", X);
|
|
return 0;
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// Main driver code.
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
int main() {
|
|
// Install standard binary operators.
|
|
// 1 is lowest precedence.
|
|
BinopPrecedence['='] = 2;
|
|
BinopPrecedence['<'] = 10;
|
|
BinopPrecedence['+'] = 20;
|
|
BinopPrecedence['-'] = 20;
|
|
BinopPrecedence['*'] = 40; // highest.
|
|
|
|
// Prime the first token.
|
|
fprintf(stderr, "ready> ");
|
|
getNextToken();
|
|
|
|
// Make the module, which holds all the code.
|
|
TheModule = new Module("my cool jit");
|
|
|
|
// Create the JIT.
|
|
TheExecutionEngine = ExecutionEngine::create(TheModule);
|
|
|
|
{
|
|
ExistingModuleProvider OurModuleProvider(TheModule);
|
|
FunctionPassManager OurFPM(&OurModuleProvider);
|
|
|
|
// Set up the optimizer pipeline. Start with registering info about how the
|
|
// target lays out data structures.
|
|
OurFPM.add(new TargetData(*TheExecutionEngine->getTargetData()));
|
|
// Promote allocas to registers.
|
|
OurFPM.add(createPromoteMemoryToRegisterPass());
|
|
// Do simple "peephole" optimizations and bit-twiddling optzns.
|
|
OurFPM.add(createInstructionCombiningPass());
|
|
// Reassociate expressions.
|
|
OurFPM.add(createReassociatePass());
|
|
// Eliminate Common SubExpressions.
|
|
OurFPM.add(createGVNPass());
|
|
// Simplify the control flow graph (deleting unreachable blocks, etc).
|
|
OurFPM.add(createCFGSimplificationPass());
|
|
|
|
// Set the global so the code gen can use this.
|
|
TheFPM = &OurFPM;
|
|
|
|
// Run the main "interpreter loop" now.
|
|
MainLoop();
|
|
|
|
TheFPM = 0;
|
|
|
|
// Print out all of the generated code.
|
|
TheModule->dump();
|
|
|
|
} // Free module provider (and thus the module) and pass manager.
|
|
|
|
return 0;
|
|
}
|
|
</pre>
|
|
</div>
|
|
|
|
<a href="LangImpl8.html">Next: Conclusion and other useful LLVM tidbits</a>
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</div>
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<address>
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<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
|
|
<a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
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Last modified: $Date: 2007-10-17 11:05:13 -0700 (Wed, 17 Oct 2007) $
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</address>
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