[LoadStoreVectorizer] Fix one-element vector handling

This is the followup of llvm#168135

Author: cmc-rep

llvm/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp

@@ -953,15 +953,15 @@ bool Vectorizer::vectorizeChain(Chain &C) {
       unsigned EOffset =
           (E.OffsetFromLeader - C[0].OffsetFromLeader).getZExtValue();
       unsigned VecIdx = 8 * EOffset / DL.getTypeSizeInBits(VecElemTy);
-      if (auto *VT = dyn_cast<FixedVectorType>(T)) {
+      if (VecTy == VecElemTy) {
+        V = VecInst;
+      } else if (auto *VT = dyn_cast<FixedVectorType>(T)) {
         auto Mask = llvm::to_vector<8>(
             llvm::seq<int>(VecIdx, VecIdx + VT->getNumElements()));
         V = Builder.CreateShuffleVector(VecInst, Mask, I->getName());
-      } else if (VecTy != VecElemTy) {
+      } else {
         V = Builder.CreateExtractElement(VecInst, Builder.getInt32(VecIdx),
                                          I->getName());
-      } else {
-        V = VecInst;
       }
       if (V->getType() != I->getType())
         V = Builder.CreateBitOrPointerCast(V, I->getType());

llvm/test/Transforms/LoadStoreVectorizer/AMDGPU/vectorize-redund-loads.ll

@@ -1,6 +1,33 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
 ; RUN: opt -mtriple=amdgcn-amd-amdhsa -passes=load-store-vectorizer -S -o - %s | FileCheck %s
 
+define void @onevec(ptr %ptr) {
+; CHECK-LABEL: define void @onevec(
+; CHECK-SAME: ptr [[PTR:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = load i32, ptr [[PTR]], align 4
+; CHECK-NEXT:    [[TMP2:%.*]] = bitcast i32 [[TMP1]] to <1 x i32>
+; CHECK-NEXT:    [[GEP1:%.*]] = getelementptr inbounds i8, ptr [[PTR]], i32 16
+; CHECK-NEXT:    [[TMP3:%.*]] = load i32, ptr [[GEP1]], align 4
+; CHECK-NEXT:    [[TMP4:%.*]] = bitcast i32 [[TMP3]] to <1 x i32>
+; CHECK-NEXT:    [[GEP2:%.*]] = getelementptr inbounds i8, ptr [[PTR]], i32 32
+; CHECK-NEXT:    [[TMP5:%.*]] = load i32, ptr [[GEP2]], align 4
+; CHECK-NEXT:    [[TMP6:%.*]] = bitcast i32 [[TMP5]] to <1 x i32>
+; CHECK-NEXT:    [[TMP7:%.*]] = bitcast i32 [[TMP5]] to <1 x i32>
+; CHECK-NEXT:    ret void
+;
+  %ld0 = load <1 x i32>, ptr %ptr, align 4
+  %ld1 = load i32, ptr %ptr, align 4
+
+  %gep1 = getelementptr inbounds i8, ptr %ptr, i32 16
+  %ld2 = load i32, ptr %gep1, align 4
+  %ld3 = load <1 x i32>, ptr %gep1, align 4
+
+  %gep2 = getelementptr inbounds i8, ptr %ptr, i32 32
+  %ld4 = load <1 x i32>, ptr %gep2, align 4
+  %ld5 = load <1 x i32>, ptr %gep2, align 4
+  ret void
+}
+
 define void @test(ptr %ptr) {
 ; CHECK-LABEL: define void @test(
 ; CHECK-SAME: ptr [[PTR:%.*]]) {