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

1 files changed, 11 insertions, 6 deletions

diff --git a/llvm/lib/Transforms/Utils/DemoteRegToStack.cpp b/llvm/lib/Transforms/Utils/DemoteRegToStack.cpp
index 75a1dde57c4..0eee6e19efa 100644
--- a/llvm/lib/Transforms/Utils/DemoteRegToStack.cpp
+++ b/llvm/lib/Transforms/Utils/DemoteRegToStack.cpp
@@ -28,15 +28,17 @@ AllocaInst *llvm::DemoteRegToStack(Instruction &I, bool VolatileLoads,
     return nullptr;
   }
 
+  Function *F = I.getParent()->getParent();
+  const DataLayout &DL = F->getParent()->getDataLayout();
+
   // Create a stack slot to hold the value.
   AllocaInst *Slot;
   if (AllocaPoint) {
-    Slot = new AllocaInst(I.getType(), nullptr,
+    Slot = new AllocaInst(I.getType(), DL.getAllocaAddrSpace(), nullptr,
                           I.getName()+".reg2mem", AllocaPoint);
   } else {
-    Function *F = I.getParent()->getParent();
-    Slot = new AllocaInst(I.getType(), nullptr, I.getName() + ".reg2mem",
-                          &F->getEntryBlock().front());
+    Slot = new AllocaInst(I.getType(), DL.getAllocaAddrSpace(), nullptr,
+                          I.getName() + ".reg2mem", &F->getEntryBlock().front());
   }
 
   // We cannot demote invoke instructions to the stack if their normal edge
@@ -110,14 +112,17 @@ AllocaInst *llvm::DemotePHIToStack(PHINode *P, Instruction *AllocaPoint) {
     return nullptr;
   }
 
+  const DataLayout &DL = P->getModule()->getDataLayout();
+
   // Create a stack slot to hold the value.
   AllocaInst *Slot;
   if (AllocaPoint) {
-    Slot = new AllocaInst(P->getType(), nullptr,
+    Slot = new AllocaInst(P->getType(), DL.getAllocaAddrSpace(), nullptr,
                           P->getName()+".reg2mem", AllocaPoint);
   } else {
     Function *F = P->getParent()->getParent();
-    Slot = new AllocaInst(P->getType(), nullptr, P->getName() + ".reg2mem",
+    Slot = new AllocaInst(P->getType(), DL.getAllocaAddrSpace(), nullptr,
+                          P->getName() + ".reg2mem",
                           &F->getEntryBlock().front());
   }