[AMDGPU] stop buffer_store being moved illegally

Summary:
The machine instruction scheduler was illegally moving a buffer store
past a buffer load with the same descriptor and offset. Fixed by marking
buffer ops as mayAlias and isAliased. This may be overly conservative,
and we may need to revisit.

Subscribers: arsenm, kzhuravl, wdng, nhaehnle, yaxunl, dstuttard, t-tye, llvm-commits

Differential Revision: https://reviews.llvm.org/D43332

Change-Id: Iff3173d9e0653e830474546276ab9d30318b8ef7
llvm-svn: 325567

1 files changed, 2 insertions, 6 deletions

diff --git a/llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.h b/llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.h
index 6eed4fcd8ad..781eea0f94b 100644
--- a/llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.h
+++ b/llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.h
@@ -70,15 +70,11 @@ public:
   }
 
   bool isAliased(const MachineFrameInfo *) const override {
-    // FIXME: If we ever change image intrinsics to accept fat pointers, then
-    // this could be true for some cases.
-    return false;
+    return true;
   }
 
   bool mayAlias(const MachineFrameInfo *) const override {
-    // FIXME: If we ever change image intrinsics to accept fat pointers, then
-    // this could be true for some cases.
-    return false;
+    return true;
   }
 };