makes it so that it constant folds instructions on the fly. This is good
for several reasons:
0. Many instructions are constant foldable after inlining, particularly if
inlining a call with constant arguments.
1. Without this, the inliner has to allocate memory for all of the instructions
that can be constant folded, then a subsequent pass has to delete them. This
gets the job done without this extra work.
2. This makes the inliner *pass* a bit more aggressive: in particular, it
partially solves a phase order issue where the inliner would inline lots
of code that folds away to nothing, but think that the resultant function
is big because of this code that will be gone. Now the code never exists.
This is the first part of a 2-step process. The second part will be smart
enough to see when this implicit constant folding propagates a constant into
a branch or switch instruction, making CFG edges dead.
This implements Transforms/Inline/inline_constprop.ll
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it doesn't contain any calls. This is a fairly common case for C++ code,
so it will probably speed up the inliner marginally in these cases.
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function was not an alloca, we wouldn't check the entry block for any allocas,
leading to increased stack space in some cases. In practice, allocas are almost
always at the top of the block, so this was never noticed.
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using Function::arg_{iterator|begin|end}. Likewise Module::g* -> Module::global_*.
This patch is contributed by Gabor Greif, thanks!
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If a function had no return instruction in it, and the result of the inlined
call instruction was used, we would crash.
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Basically we were using SimplifyCFG as a huge sledgehammer for a simple
optimization. Because simplifycfg does so many things, we can't use it
for this purpose.
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allowed in invoke instructions. Thus, if we are inlining a call to an intrinsic
function into an invoke site, we don't need to turn the call into an invoke!
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1. Don't scan to the end of alloca instructions in the caller function to
insert inlined allocas, just insert at the top. This saves a lot of
time inlining into functions with a lot of allocas.
2. Use splice to move the alloca instructions over, instead of remove/insert.
This allows us to transfer a block at a time, and eliminates a bunch of
silly symbol table manipulations.
This speeds up the inliner on the testcase in PR209 from 1.73s -> 1.04s (67%)
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and that basic block ends with a return instruction. In this case, we can just splice
the cloned "body" of the function directly into the source basic block, avoiding a lot
of rearrangement and splitBasicBlock's linear scan over the split block. This speeds up
the inliner on the testcase in PR209 from 2.3s to 1.7s, a 35% reduction.
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before we delete the original call site, allowing slight simplifications of
code, but nothing exciting.
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process. The only optimization we did so far is to avoid creating a
PHI node, then immediately destroying it in the common case where the
callee has one return statement. Instead, we just don't create the return
value. This has no noticable performance impact, but paves the way for
future improvements.
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PHI node entries for unwind instructions just like for call instructions which
became invokes! This fixes PR57, tested by
Inline/2003-10-26-InlineInvokeExceptionDestPhi.ll
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break dominance relationships, and is otherwise bad. This fixes bug:
Inline/2003-10-13-AllocaDominanceProblem.ll. This also fixes miscompilation
of 3 176.gcc source files (reload1.c, global.c, flow.c)
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Running the inliner on 252.eon used to take 48.4763s, now it takes 14.4148s.
In release mode, it went from taking 25.8741s to taking 11.5712s.
This also fixes a FIXME.
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... by making sure to update PHI nodes to take into consideration the
extra edges we get if we inline a call instruction through an invoke.
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