AMDGPU: Fix emitting multiple stack loads for stack passed workitems

The same stack is loaded for each workitem ID, and each use. Nothing
prevents you from creating multiple fixed stack objects with the same
offsets, so this was creating a load for each unique frame index,
despite them being the same offset. Re-use the same frame index so the
loads are CSEable.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@371148 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/AMDGPU/AMDGPUISelLowering.cpp b/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
index a9596b95c367926c5c866fb0fa2f95d37294b488..04f1da23872c13d61ef0c3ac4c1c3d344bdc8059 100644 (file)
--- a/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
+++ b/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
@@ -4162,14 +4162,28 @@ SDValue AMDGPUTargetLowering::CreateLiveInRegister(SelectionDAG &DAG,
   return DAG.getCopyFromReg(DAG.getEntryNode(), SL, VReg, VT);
 }
 
+// This may be called multiple times, and nothing prevents creating multiple
+// objects at the same offset. See if we already defined this object.
+static int getOrCreateFixedStackObject(MachineFrameInfo &MFI, unsigned Size,
+                                       int64_t Offset) {
+  for (int I = MFI.getObjectIndexBegin(); I < 0; ++I) {
+    if (MFI.getObjectOffset(I) == Offset) {
+      assert(MFI.getObjectSize(I) == Size);
+      return I;
+    }
+  }
+
+  return MFI.CreateFixedObject(Size, Offset, true);
+}
+
 SDValue AMDGPUTargetLowering::loadStackInputValue(SelectionDAG &DAG,
                                                   EVT VT,
                                                   const SDLoc &SL,
                                                   int64_t Offset) const {
   MachineFunction &MF = DAG.getMachineFunction();
   MachineFrameInfo &MFI = MF.getFrameInfo();
+  int FI = getOrCreateFixedStackObject(MFI, VT.getStoreSize(), Offset);
 
-  int FI = MFI.CreateFixedObject(VT.getStoreSize(), Offset, true);
   auto SrcPtrInfo = MachinePointerInfo::getStack(MF, Offset);
   SDValue Ptr = DAG.getFrameIndex(FI, MVT::i32);
 

diff --git a/test/CodeGen/AMDGPU/callee-special-input-vgprs.ll b/test/CodeGen/AMDGPU/callee-special-input-vgprs.ll
index 2df3ad9cdefb095b288df2b1351814dd3066d1a9..d5211ceede3c454abcb71665f01ea1a817cfe259 100644 (file)
--- a/test/CodeGen/AMDGPU/callee-special-input-vgprs.ll
+++ b/test/CodeGen/AMDGPU/callee-special-input-vgprs.ll
@@ -543,19 +543,25 @@ define void @func_call_too_many_args_use_workitem_id_x_byval() #1 {
   ret void
 }
 
+; Only one stack load should be emitted for all 3 values.
 ; GCN-LABEL: {{^}}too_many_args_use_workitem_id_xyz:
-; GCN: buffer_store_dword v32, off, s[0:3], s32 offset:4 ; 4-byte Folded Spill
-; GCN: buffer_load_dword v32, off, s[0:3], s32{{$}}
-; GCN: v_and_b32_e32 v32, 0x3ff, v32
-; GCN: {{flat|global}}_store_dword v{{\[[0-9]+:[0-9]+]}}, v32
-; GCN: buffer_load_dword v32, off, s[0:3], s32{{$}}
-; GCN: v_bfe_u32 v32, v32, 10, 10
-; GCN: {{flat|global}}_store_dword v{{\[[0-9]+:[0-9]+]}}, v32
+; GCN: buffer_store_dword v32, off, s[0:3], s32 offset:8 ; 4-byte Folded Spill
+; GCN: buffer_store_dword v33, off, s[0:3], s32 offset:4 ; 4-byte Folded Spill
+; GCN-NOT: buffer_load_dword v{{[0-9]+}}, off, s[0:3], s32{{$}}
 ; GCN: buffer_load_dword v32, off, s[0:3], s32{{$}}
-; GCN: v_bfe_u32 v32, v32, 20, 10
-; GCN: {{flat|global}}_store_dword v{{\[[0-9]+:[0-9]+]}}, v32
-
-; GCN: buffer_load_dword v32, off, s[0:3], s32 offset:4 ; 4-byte Folded Reload
+; GCN-NOT: buffer_load_dword
+
+; GCN: v_and_b32_e32 [[AND_X:v[0-9]+]], 0x3ff, v32
+; GCN-NOT: buffer_load_dword
+; GCN: {{flat|global}}_store_dword v{{\[[0-9]+:[0-9]+]}}, [[AND_X]]
+; GCN-NOT: buffer_load_dword
+; GCN: v_bfe_u32 [[BFE_Y:v[0-9]+]], v32, 10, 10
+; GCN-NEXT: v_bfe_u32 [[BFE_Z:v[0-9]+]], v32, 20, 10
+; GCN-NEXT: {{flat|global}}_store_dword v{{\[[0-9]+:[0-9]+]}}, [[BFE_Y]]
+; GCN-NEXT: {{flat|global}}_store_dword v{{\[[0-9]+:[0-9]+]}}, [[BFE_Z]]
+
+; GCN: buffer_load_dword v33, off, s[0:3], s32 offset:4 ; 4-byte Folded Reload
+; GCN: buffer_load_dword v32, off, s[0:3], s32 offset:8 ; 4-byte Folded Reload
 ; GCN-NEXT: s_waitcnt
 ; GCN-NEXT: s_setpc_b64
 define void @too_many_args_use_workitem_id_xyz(