[PATCH] D62613: [DAGCombiner] Replace gathers with a zero mask with the passthru value

[Benjamin Kramer via Phabricator via llvm-commits]

bkramer updated this revision to Diff 202009.
bkramer added a comment.

Use isBuildVectorAllZeros, drop isNullOrNullSplat change.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D62613/new/

https://reviews.llvm.org/D62613

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/test/CodeGen/X86/avx2-masked-gather.ll


Index: llvm/test/CodeGen/X86/avx2-masked-gather.ll
===================================================================
--- llvm/test/CodeGen/X86/avx2-masked-gather.ll
+++ llvm/test/CodeGen/X86/avx2-masked-gather.ll
@@ -769,3 +769,24 @@
   ret <2 x double> %res
 }
 
+
+define <2 x double> @masked_gather_zeromask(<2 x double*>* %ptr, <2 x double> %dummy, <2 x double> %passthru) {
+; X86-LABEL: masked_gather_zeromask:
+; X86:       # %bb.0: # %entry
+; X86-NEXT:    vmovaps %xmm1, %xmm0
+; X86-NEXT:    retl
+;
+; X64-LABEL: masked_gather_zeromask:
+; X64:       # %bb.0: # %entry
+; X64-NEXT:    vmovaps %xmm1, %xmm0
+; X64-NEXT:    retq
+;
+; NOGATHER-LABEL: masked_gather_zeromask:
+; NOGATHER:       # %bb.0: # %entry
+; NOGATHER-NEXT:    vmovaps %xmm1, %xmm0
+; NOGATHER-NEXT:    retq
+entry:
+  %ld  = load <2 x double*>, <2 x double*>* %ptr
+  %res = call <2 x double> @llvm.masked.gather.v2double(<2 x double*> %ld, i32 0, <2 x i1> zeroinitializer, <2 x double> %passthru)
+  ret <2 x double> %res
+}
Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -8084,13 +8084,17 @@
 }
 
 SDValue DAGCombiner::visitMGATHER(SDNode *N) {
-  if (Level >= AfterLegalizeTypes)
-    return SDValue();
-
   MaskedGatherSDNode *MGT = cast<MaskedGatherSDNode>(N);
   SDValue Mask = MGT->getMask();
   SDLoc DL(N);
 
+  // Zap gathers with a zero mask.
+  if (ISD::isBuildVectorAllZeros(Mask.getNode()))
+    return CombineTo(N, MGT->getPassThru(), MGT->getChain());
+
+  if (Level >= AfterLegalizeTypes)
+    return SDValue();
+
   // If the MGATHER result requires splitting and the mask is provided by a
   // SETCC, then split both nodes and its operands before legalization. This
   // prevents the type legalizer from unrolling SETCC into scalar comparisons


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