[SLP] Fix PR38339: Instruction does not dominate all uses!

Summary:
If the ExtractElement instructions can be optimized out during the
vectorization and we need to reshuffle the parent vector, this
ShuffleInstruction may be inserted in the wrong place causing compiler
to produce incorrect code.

Reviewers: spatel, RKSimon, mkuper, hfinkel, javed.absar

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D49928

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@338380 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Vectorize/SLPVectorizer.cpp b/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 1ea12a38834079eba7e1bfbf3eac73d10e0deca7..5c2efe885e222c8fee86688c9d2f05731e919bea 100644 (file)
--- a/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -3111,6 +3111,12 @@ Value *BoUpSLP::vectorizeTree(TreeEntry *E) {
           // TODO: Merge this shuffle with the ReorderShuffleMask.
           if (!E->ReorderIndices.empty())
             Builder.SetInsertPoint(VL0);
+          else if (auto *I = dyn_cast<Instruction>(V))
+            Builder.SetInsertPoint(I->getParent(),
+                                   std::next(I->getIterator()));
+          else
+            Builder.SetInsertPoint(&F->getEntryBlock(),
+                                   F->getEntryBlock().getFirstInsertionPt());
           V = Builder.CreateShuffleVector(V, UndefValue::get(VecTy),
                                           E->ReuseShuffleIndices, "shuffle");
         }

diff --git a/test/Transforms/SLPVectorizer/AArch64/PR38339.ll b/test/Transforms/SLPVectorizer/AArch64/PR38339.ll
new file mode 100644 (file)
index 0000000..1ab4a13
--- /dev/null
+++ b/test/Transforms/SLPVectorizer/AArch64/PR38339.ll
@@ -0,0 +1,29 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -slp-vectorizer -S -mtriple=aarch64-apple-ios -mcpu=cyclone -o - %s | FileCheck %s
+
+define void @f1(<2 x i16> %x, i16* %a) {
+; CHECK-LABEL: @f1(
+; CHECK-NEXT:    [[SHUFFLE:%.*]] = shufflevector <2 x i16> [[X:%.*]], <2 x i16> undef, <4 x i32> <i32 0, i32 1, i32 1, i32 0>
+; CHECK-NEXT:    [[PTR0:%.*]] = getelementptr inbounds [4 x i16], [4 x i16]* undef, i16 0, i16 0
+; CHECK-NEXT:    [[PTR1:%.*]] = getelementptr inbounds [4 x i16], [4 x i16]* undef, i16 0, i16 1
+; CHECK-NEXT:    [[PTR2:%.*]] = getelementptr inbounds [4 x i16], [4 x i16]* undef, i16 0, i16 2
+; CHECK-NEXT:    [[PTR3:%.*]] = getelementptr inbounds [4 x i16], [4 x i16]* undef, i16 0, i16 3
+; CHECK-NEXT:    [[TMP1:%.*]] = extractelement <4 x i16> [[SHUFFLE]], i32 0
+; CHECK-NEXT:    store i16 [[TMP1]], i16* [[A:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = bitcast i16* [[PTR0]] to <4 x i16>*
+; CHECK-NEXT:    store <4 x i16> [[SHUFFLE]], <4 x i16>* [[TMP2]], align 2
+; CHECK-NEXT:    ret void
+;
+  %t2 = extractelement <2 x i16> %x, i32 0
+  %t3 = extractelement <2 x i16> %x, i32 1
+  %ptr0 = getelementptr inbounds [4 x i16], [4 x i16]* undef, i16 0, i16 0
+  %ptr1 = getelementptr inbounds [4 x i16], [4 x i16]* undef, i16 0, i16 1
+  %ptr2 = getelementptr inbounds [4 x i16], [4 x i16]* undef, i16 0, i16 2
+  %ptr3 = getelementptr inbounds [4 x i16], [4 x i16]* undef, i16 0, i16 3
+  store i16 %t2, i16* %a
+  store i16 %t2, i16* %ptr0
+  store i16 %t3, i16* %ptr1
+  store i16 %t3, i16* %ptr2
+  store i16 %t2, i16* %ptr3
+  ret void
+}