Add default address space for functions to the data layout (1/3)

Summary:
This adds initial support for letting targets specify which address
spaces their functions should reside in by default.

If a function is created by a frontend, it will get the default address space specified in the DataLayout, unless the frontend explicitly uses a more general `llvm::Function` constructor. Function address spaces will become a part of the bitcode and textual IR forms, as we do not have access to a data layout whilst parsing LL.

It will be possible to write IR that explicitly has `addrspace(n)` on a function. In this case, the function will reside in the specified space, ignoring the default in the DL.

This is the first step towards placing functions into the correct
address space for Harvard architectures.

Full patchset
* Add program address space to data layout D37052
* Require address space to be specified when creating functions D37054
* [clang] Require address space to be specified when creating functions D37057

Reviewers: pcc, arsenm, kparzysz, hfinkel, theraven

Reviewed By: theraven

Subscribers: arichardson, simoncook, rengolin, wdng, uabelho, bjope, asb, llvm-commits

Differential Revision: https://reviews.llvm.org/D37052

llvm-svn: 325479

docs/LangRef.rst

@@ -1905,8 +1905,15 @@ as follows:
     must be a multiple of 8-bits. If omitted, the natural stack
     alignment defaults to "unspecified", which does not prevent any
     alignment promotions.
+``P<address space>``
+    Specifies the address space that corresponds to program memory.
+    Harvard architectures can use this to specify what space LLVM
+    should place things such as functions into. If omitted, the
+    program memory space defaults to the default address space of 0,
+    which corresponds to a Von Neumann architecture that has code
+    and data in the same space.
 ``A<address space>``
-    Specifies the address space of  objects created by '``alloca``'.
+    Specifies the address space of objects created by '``alloca``'.
     Defaults to the default address space of 0.
 ``p[n]:<size>:<abi>:<pref>:<idx>``
     This specifies the *size* of a pointer and its ``<abi>`` and

include/llvm/IR/DataLayout.h

@@ -115,6 +115,7 @@ private:
 
   unsigned AllocaAddrSpace;
   unsigned StackNaturalAlign;
+  unsigned ProgramAddrSpace;
 
   enum ManglingModeT {
     MM_None,
@@ -199,6 +200,7 @@ public:
     BigEndian = DL.isBigEndian();
     AllocaAddrSpace = DL.AllocaAddrSpace;
     StackNaturalAlign = DL.StackNaturalAlign;
+    ProgramAddrSpace = DL.ProgramAddrSpace;
     ManglingMode = DL.ManglingMode;
     LegalIntWidths = DL.LegalIntWidths;
     Alignments = DL.Alignments;
@@ -255,6 +257,8 @@ public:
   unsigned getStackAlignment() const { return StackNaturalAlign; }
   unsigned getAllocaAddrSpace() const { return AllocaAddrSpace; }
 
+  unsigned getProgramAddressSpace() const { return ProgramAddrSpace; }
+
   bool hasMicrosoftFastStdCallMangling() const {
     return ManglingMode == MM_WinCOFFX86;
   }

lib/IR/DataLayout.cpp

@@ -184,6 +184,7 @@ void DataLayout::reset(StringRef Desc) {
   BigEndian = false;
   AllocaAddrSpace = 0;
   StackNaturalAlign = 0;
+  ProgramAddrSpace = 0;
   ManglingMode = MM_None;
   NonIntegralAddressSpaces.clear();
 
@@ -224,6 +225,13 @@ static unsigned inBytes(unsigned Bits) {
   return Bits / 8;
 }
 
+static unsigned getAddrSpace(StringRef R) {
+  unsigned AddrSpace = getInt(R);
+  if (!isUInt<24>(AddrSpace))
+    report_fatal_error("Invalid address space, must be a 24-bit integer");
+  return AddrSpace;
+}
+
 void DataLayout::parseSpecifier(StringRef Desc) {
   StringRepresentation = Desc;
   while (!Desc.empty()) {
@@ -372,10 +380,12 @@ void DataLayout::parseSpecifier(StringRef Desc) {
       StackNaturalAlign = inBytes(getInt(Tok));
       break;
     }
+    case 'P': { // Function address space.
+      ProgramAddrSpace = getAddrSpace(Tok);
+      break;
+    }
     case 'A': { // Default stack/alloca address space.
-      AllocaAddrSpace = getInt(Tok);
-      if (!isUInt<24>(AllocaAddrSpace))
-        report_fatal_error("Invalid address space, must be a 24bit integer");
+      AllocaAddrSpace = getAddrSpace(Tok);
       break;
     }
     case 'm':
@@ -422,6 +432,7 @@ bool DataLayout::operator==(const DataLayout &Other) const {
   bool Ret = BigEndian == Other.BigEndian &&
              AllocaAddrSpace == Other.AllocaAddrSpace &&
              StackNaturalAlign == Other.StackNaturalAlign &&
+             ProgramAddrSpace == Other.ProgramAddrSpace &&
              ManglingMode == Other.ManglingMode &&
              LegalIntWidths == Other.LegalIntWidths &&
              Alignments == Other.Alignments && Pointers == Other.Pointers;

test/Assembler/datalayout-program-addrspace.ll

@@ -0,0 +1,5 @@
+; RUN: llvm-as < %s | llvm-dis | FileCheck %s
+
+; CHECK: target datalayout = "P1"
+target datalayout = "P1"
+

test/Assembler/invalid-datalayout-alloca-addrspace.ll

@@ -1,4 +1,4 @@
 ; RUN: not llvm-as < %s 2>&1 | FileCheck %s
 
 target datalayout = "A16777216"
-; CHECK: Invalid address space, must be a 24bit integer
+; CHECK: Invalid address space, must be a 24-bit integer

test/Assembler/invalid-datalayout-program-addrspace.ll

@@ -0,0 +1,4 @@
+; RUN: not llvm-as < %s 2>&1 | FileCheck %s
+
+; CHECK: Invalid address space, must be a 24-bit integer
+target datalayout = "P16777216"