Allow DataLayout to specify addrspace for allocas.

LLVM makes several assumptions about address space 0. However,
alloca is presently constrained to always return this address space.
There's no real way to avoid using alloca, so without this
there is no way to opt out of these assumptions.

The problematic assumptions include:
- That the pointer size used for the stack is the same size as
  the code size pointer, which is also the maximum sized pointer.

- That 0 is an invalid, non-dereferencable pointer value.

These are problems for AMDGPU because alloca is used to
implement the private address space, which uses a 32-bit
index as the pointer value. Other pointers are 64-bit
and behave more like LLVM's notion of generic address
space. By changing the address space used for allocas,
we can change our generic pointer type to be LLVM's generic
pointer type which does have similar properties.

llvm-svn: 299888

2 files changed, 51 insertions, 4 deletions

diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index d8f6c1c5146..941ee347a78 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -1852,6 +1852,34 @@ bool LLParser::ParseOptionalCommaAlign(unsigned &Alignment,
   return false;
 }
 
+/// ParseOptionalCommaAddrSpace
+///   ::=
+///   ::= ',' addrspace(1)
+///
+/// This returns with AteExtraComma set to true if it ate an excess comma at the
+/// end.
+bool LLParser::ParseOptionalCommaAddrSpace(unsigned &AddrSpace,
+                                           LocTy &Loc,
+                                           bool &AteExtraComma) {
+  AteExtraComma = false;
+  while (EatIfPresent(lltok::comma)) {
+    // Metadata at the end is an early exit.
+    if (Lex.getKind() == lltok::MetadataVar) {
+      AteExtraComma = true;
+      return false;
+    }
+
+    Loc = Lex.getLoc();
+    if (Lex.getKind() != lltok::kw_addrspace)
+      return Error(Lex.getLoc(), "expected metadata or 'addrspace'");
+
+    if (ParseOptionalAddrSpace(AddrSpace))
+      return true;
+  }
+
+  return false;
+}
+
 bool LLParser::parseAllocSizeArguments(unsigned &BaseSizeArg,
                                        Optional<unsigned> &HowManyArg) {
   Lex.Lex();
@@ -6033,8 +6061,9 @@ bool LLParser::ParseCall(Instruction *&Inst, PerFunctionState &PFS,
 ///       (',' 'align' i32)?
 int LLParser::ParseAlloc(Instruction *&Inst, PerFunctionState &PFS) {
   Value *Size = nullptr;
-  LocTy SizeLoc, TyLoc;
+  LocTy SizeLoc, TyLoc, ASLoc;
   unsigned Alignment = 0;
+  unsigned AddrSpace = 0;
   Type *Ty = nullptr;
 
   bool IsInAlloca = EatIfPresent(lltok::kw_inalloca);
@@ -6048,12 +6077,21 @@ int LLParser::ParseAlloc(Instruction *&Inst, PerFunctionState &PFS) {
   bool AteExtraComma = false;
   if (EatIfPresent(lltok::comma)) {
     if (Lex.getKind() == lltok::kw_align) {
-      if (ParseOptionalAlignment(Alignment)) return true;
+      if (ParseOptionalAlignment(Alignment))
+        return true;
+      if (ParseOptionalCommaAddrSpace(AddrSpace, ASLoc, AteExtraComma))
+        return true;
+    } else if (Lex.getKind() == lltok::kw_addrspace) {
+      ASLoc = Lex.getLoc();
+      if (ParseOptionalAddrSpace(AddrSpace))
+        return true;
     } else if (Lex.getKind() == lltok::MetadataVar) {
       AteExtraComma = true;
     } else {
       if (ParseTypeAndValue(Size, SizeLoc, PFS) ||
-          ParseOptionalCommaAlign(Alignment, AteExtraComma))
+          ParseOptionalCommaAlign(Alignment, AteExtraComma) ||
+          (!AteExtraComma &&
+           ParseOptionalCommaAddrSpace(AddrSpace, ASLoc, AteExtraComma)))
         return true;
     }
   }
@@ -6061,7 +6099,14 @@ int LLParser::ParseAlloc(Instruction *&Inst, PerFunctionState &PFS) {
   if (Size && !Size->getType()->isIntegerTy())
     return Error(SizeLoc, "element count must have integer type");
 
-  AllocaInst *AI = new AllocaInst(Ty, Size, Alignment);
+  const DataLayout &DL = M->getDataLayout();
+  unsigned AS = DL.getAllocaAddrSpace();
+  if (AS != AddrSpace) {
+    // TODO: In the future it should be possible to specify addrspace per-alloca.
+    return Error(ASLoc, "address space must match datalayout");
+  }
+
+  AllocaInst *AI = new AllocaInst(Ty, AS, Size, Alignment);
   AI->setUsedWithInAlloca(IsInAlloca);
   AI->setSwiftError(IsSwiftError);
   Inst = AI;
diff --git a/llvm/lib/AsmParser/LLParser.h b/llvm/lib/AsmParser/LLParser.h
index 3a794142172..5293bda1b70 100644
--- a/llvm/lib/AsmParser/LLParser.h
+++ b/llvm/lib/AsmParser/LLParser.h
@@ -246,6 +246,8 @@ namespace llvm {
     bool ParseOrdering(AtomicOrdering &Ordering);
     bool ParseOptionalStackAlignment(unsigned &Alignment);
     bool ParseOptionalCommaAlign(unsigned &Alignment, bool &AteExtraComma);
+    bool ParseOptionalCommaAddrSpace(unsigned &AddrSpace, LocTy &Loc,
+                                     bool &AteExtraComma);
     bool ParseOptionalCommaInAlloca(bool &IsInAlloca);
     bool parseAllocSizeArguments(unsigned &ElemSizeArg,
                                  Optional<unsigned> &HowManyArg);