[VectorCombine] Add option to only run scalarization transforms.

fhahn · fhahn · commit 9594c697967e · 2021-10-17T23:04:52.000+01:00
This patch adds a pass option to only run transforms that scalarize vector operations and do not create new vector instructions. When running VectorCombine early in the pipeline introducing new vector operations can have negative effects, like blocking loop or SLP vectorization. To avoid regressions, restrict the early VectorCombine run (when using -enable-matrix) to only perform scalarization and not introduce new vector operations. This is done as option to the pass directly, which is then set when adding the pass to the pipeline. This is done for the new pass manager only. Reviewed By: spatel Differential Revision: https://reviews.llvm.org/D111800 (cherry-picked from 4a1d63d)
diff --git a/llvm/include/llvm/Transforms/Vectorize/VectorCombine.h b/llvm/include/llvm/Transforms/Vectorize/VectorCombine.h
@@ -20,10 +20,16 @@
 namespace llvm {
 
 /// Optimize scalar/vector interactions in IR using target cost models.
-struct VectorCombinePass : public PassInfoMixin<VectorCombinePass> {
+class VectorCombinePass : public PassInfoMixin<VectorCombinePass> {
+  /// If true only perform scalarization combines and do not introduce new
+  /// vector operations.
+  bool ScalarizationOnly;
+
 public:
+  VectorCombinePass(bool ScalarizationOnly = false)
+      : ScalarizationOnly(ScalarizationOnly) {}
+
   PreservedAnalyses run(Function &F, FunctionAnalysisManager &);
 };
-
 }
 #endif // LLVM_TRANSFORMS_VECTORIZE_VECTORCOMBINE_H
diff --git a/llvm/lib/Passes/PassBuilder.cpp b/llvm/lib/Passes/PassBuilder.cpp
@@ -809,7 +809,7 @@ PassBuilder::buildFunctionSimplificationPipeline(OptimizationLevel Level,
   // The matrix extension can introduce large vector operations early, which can
   // benefit from running vector-combine early on.
   if (EnableMatrix)
-    FPM.addPass(VectorCombinePass());
+    FPM.addPass(VectorCombinePass(/*ScalarizationOnly=*/true));
 
   // Eliminate redundancies.
   FPM.addPass(MergedLoadStoreMotionPass());
diff --git a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
@@ -63,8 +63,10 @@ namespace {
 class VectorCombine {
 public:
   VectorCombine(Function &F, const TargetTransformInfo &TTI,
-                const DominatorTree &DT, AAResults &AA, AssumptionCache &AC)
-      : F(F), Builder(F.getContext()), TTI(TTI), DT(DT), AA(AA), AC(AC) {}
+                const DominatorTree &DT, AAResults &AA, AssumptionCache &AC,
+                bool ScalarizationOnly)
+      : F(F), Builder(F.getContext()), TTI(TTI), DT(DT), AA(AA), AC(AC),
+        ScalarizationOnly(ScalarizationOnly) {}
 
   bool run();
 
@@ -75,6 +77,11 @@ class VectorCombine {
   const DominatorTree &DT;
   AAResults &AA;
   AssumptionCache &AC;
+
+  /// If true only perform scalarization combines and do not introduce new
+  /// vector operations.
+  bool ScalarizationOnly;
+
   InstructionWorklist Worklist;
 
   bool vectorizeLoadInsert(Instruction &I);
@@ -1063,11 +1070,13 @@ bool VectorCombine::run() {
   bool MadeChange = false;
   auto FoldInst = [this, &MadeChange](Instruction &I) {
     Builder.SetInsertPoint(&I);
-    MadeChange |= vectorizeLoadInsert(I);
-    MadeChange |= foldExtractExtract(I);
-    MadeChange |= foldBitcastShuf(I);
+    if (!ScalarizationOnly) {
+      MadeChange |= vectorizeLoadInsert(I);
+      MadeChange |= foldExtractExtract(I);
+      MadeChange |= foldBitcastShuf(I);
+      MadeChange |= foldExtractedCmps(I);
+    }
     MadeChange |= scalarizeBinopOrCmp(I);
-    MadeChange |= foldExtractedCmps(I);
     MadeChange |= scalarizeLoadExtract(I);
     MadeChange |= foldSingleElementStore(I);
   };
@@ -1129,7 +1138,7 @@ class VectorCombineLegacyPass : public FunctionPass {
     auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
     auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
     auto &AA = getAnalysis<AAResultsWrapperPass>().getAAResults();
-    VectorCombine Combiner(F, TTI, DT, AA, AC);
+    VectorCombine Combiner(F, TTI, DT, AA, AC, false);
     return Combiner.run();
   }
 };
@@ -1153,7 +1162,7 @@ PreservedAnalyses VectorCombinePass::run(Function &F,
   TargetTransformInfo &TTI = FAM.getResult<TargetIRAnalysis>(F);
   DominatorTree &DT = FAM.getResult<DominatorTreeAnalysis>(F);
   AAResults &AA = FAM.getResult<AAManager>(F);
-  VectorCombine Combiner(F, TTI, DT, AA, AC);
+  VectorCombine Combiner(F, TTI, DT, AA, AC, ScalarizationOnly);
   if (!Combiner.run())
     return PreservedAnalyses::all();
   PreservedAnalyses PA;
diff --git a/llvm/test/Transforms/PhaseOrdering/AArch64/matrix-extract-insert.ll b/llvm/test/Transforms/PhaseOrdering/AArch64/matrix-extract-insert.ll
@@ -308,18 +308,16 @@ declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture) #1
 
 define <4 x float> @reverse_hadd_v4f32(<4 x float> %a, <4 x float> %b) {
 ; CHECK-LABEL: @reverse_hadd_v4f32(
-; CHECK-NEXT:    [[SHIFT:%.*]] = shufflevector <4 x float> [[A:%.*]], <4 x float> poison, <4 x i32> <i32 1, i32 undef, i32 undef, i32 undef>
-; CHECK-NEXT:    [[TMP1:%.*]] = fadd <4 x float> [[SHIFT]], [[A]]
-; CHECK-NEXT:    [[SHIFT1:%.*]] = shufflevector <4 x float> [[A]], <4 x float> poison, <4 x i32> <i32 undef, i32 undef, i32 3, i32 undef>
-; CHECK-NEXT:    [[TMP2:%.*]] = fadd <4 x float> [[SHIFT1]], [[A]]
-; CHECK-NEXT:    [[TMP3:%.*]] = shufflevector <4 x float> [[TMP1]], <4 x float> [[TMP2]], <4 x i32> <i32 undef, i32 undef, i32 6, i32 0>
-; CHECK-NEXT:    [[SHIFT2:%.*]] = shufflevector <4 x float> [[B:%.*]], <4 x float> poison, <4 x i32> <i32 1, i32 undef, i32 undef, i32 undef>
-; CHECK-NEXT:    [[TMP4:%.*]] = fadd <4 x float> [[SHIFT2]], [[B]]
-; CHECK-NEXT:    [[TMP5:%.*]] = shufflevector <4 x float> [[TMP3]], <4 x float> [[TMP4]], <4 x i32> <i32 undef, i32 4, i32 2, i32 3>
-; CHECK-NEXT:    [[SHIFT3:%.*]] = shufflevector <4 x float> [[B]], <4 x float> poison, <4 x i32> <i32 undef, i32 undef, i32 3, i32 undef>
-; CHECK-NEXT:    [[TMP6:%.*]] = fadd <4 x float> [[SHIFT3]], [[B]]
-; CHECK-NEXT:    [[TMP7:%.*]] = shufflevector <4 x float> [[TMP5]], <4 x float> [[TMP6]], <4 x i32> <i32 6, i32 1, i32 2, i32 3>
-; CHECK-NEXT:    ret <4 x float> [[TMP7]]
+; CHECK-NEXT:    [[TMP1:%.*]] = shufflevector <4 x float> [[A:%.*]], <4 x float> undef, <2 x i32> <i32 2, i32 0>
+; CHECK-NEXT:    [[TMP2:%.*]] = shufflevector <4 x float> [[A]], <4 x float> undef, <2 x i32> <i32 3, i32 1>
+; CHECK-NEXT:    [[TMP3:%.*]] = fadd <2 x float> [[TMP1]], [[TMP2]]
+; CHECK-NEXT:    [[TMP4:%.*]] = shufflevector <2 x float> [[TMP3]], <2 x float> poison, <4 x i32> <i32 undef, i32 undef, i32 0, i32 1>
+; CHECK-NEXT:    [[TMP5:%.*]] = shufflevector <4 x float> [[B:%.*]], <4 x float> undef, <2 x i32> <i32 2, i32 0>
+; CHECK-NEXT:    [[TMP6:%.*]] = shufflevector <4 x float> [[B]], <4 x float> undef, <2 x i32> <i32 3, i32 1>
+; CHECK-NEXT:    [[TMP7:%.*]] = fadd <2 x float> [[TMP5]], [[TMP6]]
+; CHECK-NEXT:    [[TMP8:%.*]] = shufflevector <2 x float> [[TMP7]], <2 x float> poison, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
+; CHECK-NEXT:    [[TMP9:%.*]] = shufflevector <4 x float> [[TMP8]], <4 x float> [[TMP4]], <4 x i32> <i32 0, i32 1, i32 6, i32 7>
+; CHECK-NEXT:    ret <4 x float> [[TMP9]]
 ;
   %vecext = extractelement <4 x float> %a, i32 0
   %vecext1 = extractelement <4 x float> %a, i32 1
