[llvm] r292842 - DAG: Don't fold vector extract into load if target doesn't want to

[Matt Arsenault via llvm-commits]

Author: arsenm
Date: Mon Jan 23 16:48:53 2017
New Revision: 292842

URL: http://llvm.org/viewvc/llvm-project?rev=292842&view=rev
Log:
DAG: Don't fold vector extract into load if target doesn't want to

Fixes turning a 32-bit scalar load into an extending vector load
for AMDGPU when dynamically indexing a vector.

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    llvm/trunk/test/CodeGen/AMDGPU/extract_vector_elt-i16.ll

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=292842&r1=292841&r2=292842&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Mon Jan 23 16:48:53 2017
@@ -12560,6 +12560,11 @@ SDValue DAGCombiner::ReplaceExtractVecto
   if (NewAlign > Align || !TLI.isOperationLegalOrCustom(ISD::LOAD, VecEltVT))
     return SDValue();
 
+  ISD::LoadExtType ExtTy = ResultVT.bitsGT(VecEltVT) ?
+    ISD::NON_EXTLOAD : ISD::EXTLOAD;
+  if (!TLI.shouldReduceLoadWidth(OriginalLoad, ExtTy, VecEltVT))
+    return SDValue();
+
   Align = NewAlign;
 
   SDValue NewPtr = OriginalLoad->getBasePtr();

Modified: llvm/trunk/test/CodeGen/AMDGPU/extract_vector_elt-i16.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AMDGPU/extract_vector_elt-i16.ll?rev=292842&r1=292841&r2=292842&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/AMDGPU/extract_vector_elt-i16.ll (original)
+++ llvm/trunk/test/CodeGen/AMDGPU/extract_vector_elt-i16.ll Mon Jan 23 16:48:53 2017
@@ -15,6 +15,34 @@ define void @extract_vector_elt_v2i16(i1
   ret void
 }
 
+; GCN-LABEL: {{^}}extract_vector_elt_v2i16_dynamic_sgpr:
+; GCN: s_load_dword [[VEC:s[0-9]+]]
+; GCN: s_load_dword [[IDX:s[0-9]+]]
+; GCN: s_lshr_b32 s{{[0-9]+}}, [[IDX]], 16
+; GCN: v_mov_b32_e32 [[VVEC:v[0-9]+]], [[VEC]]
+define void @extract_vector_elt_v2i16_dynamic_sgpr(i16 addrspace(1)* %out, <2 x i16> addrspace(2)* %vec.ptr, i32 %idx) #0 {
+  %vec = load <2 x i16>, <2 x i16> addrspace(2)* %vec.ptr
+  %elt = extractelement <2 x i16> %vec, i32 %idx
+  store i16 %elt, i16 addrspace(1)* %out, align 2
+  ret void
+}
+
+; GCN-LABEL: {{^}}extract_vector_elt_v2i16_dynamic_vgpr:
+; GCN: {{buffer|flat}}_load_dword [[IDX:v[0-9]+]]
+; GCN: buffer_load_dword [[VEC:v[0-9]+]]
+; GCN: v_lshrrev_b32_e32 [[ELT:v[0-9]+]], 16, [[VEC]]
+define void @extract_vector_elt_v2i16_dynamic_vgpr(i16 addrspace(1)* %out, <2 x i16> addrspace(1)* %vec.ptr, i32 addrspace(1)* %idx.ptr) #0 {
+  %tid = call i32 @llvm.amdgcn.workitem.id.x()
+  %tid.ext = sext i32 %tid to i64
+  %gep = getelementptr inbounds i32, i32 addrspace(1)* %idx.ptr, i64 %tid.ext
+  %out.gep = getelementptr inbounds i16, i16 addrspace(1)* %out, i64 %tid.ext
+  %idx = load volatile i32, i32 addrspace(1)* %gep
+  %vec = load <2 x i16>, <2 x i16> addrspace(1)* %vec.ptr
+  %elt = extractelement <2 x i16> %vec, i32 %idx
+  store i16 %elt, i16 addrspace(1)* %out.gep, align 2
+  ret void
+}
+
 ; GCN-LABEL: {{^}}extract_vector_elt_v3i16:
 ; GCN: buffer_load_ushort
 ; GCN: buffer_store_short
@@ -80,4 +108,7 @@ define void @dynamic_extract_vector_elt_
   ret void
 }
 
+declare i32 @llvm.amdgcn.workitem.id.x() #1
+
 attributes #0 = { nounwind }
+attributes #1 = { nounwind readnone }