[SLP][REVEC] The vectorized result for ShuffleVector may not be ShuffleVectorInst.

[HanKuanChen]

No description provided.

[llvmbot]

@llvm/pr-subscribers-vectorizers

@llvm/pr-subscribers-llvm-transforms

Author: Han-Kuan Chen (HanKuanChen)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/116940.diff

2 Files Affected:

• (modified) llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp (+12-9)
• (modified) llvm/test/Transforms/SLPVectorizer/revec-shufflevector.ll (+16)

diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index dc0dffd9fcbf81..22f66da190c41f 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -15713,16 +15713,19 @@ Value *BoUpSLP::vectorizeTree(TreeEntry *E, bool PostponedPHIs) {
           LLVM_DEBUG(dbgs() << "SLP: Diamond merged for " << *VL0 << ".\n");
           return E->VectorizedValue;
         }
-        assert(isa<ShuffleVectorInst>(Src) &&
-               "Not supported shufflevector usage.");
-        auto *SVSrc = cast<ShuffleVectorInst>(Src);
-        assert(isa<PoisonValue>(SVSrc->getOperand(1)) &&
-               "Not supported shufflevector usage.");
         SmallVector<int> ThisMask(calculateShufflevectorMask(E->Scalars));
-        SmallVector<int> NewMask(ThisMask.size());
-        transform(ThisMask, NewMask.begin(),
-                  [&SVSrc](int Mask) { return SVSrc->getShuffleMask()[Mask]; });
-        V = Builder.CreateShuffleVector(SVSrc->getOperand(0), NewMask);
+        if (isa<ShuffleVectorInst>(Src)) {
+          auto *SVSrc = cast<ShuffleVectorInst>(Src);
+          assert(isa<PoisonValue>(SVSrc->getOperand(1)) &&
+                 "Not supported shufflevector usage.");
+          SmallVector<int> NewMask(ThisMask.size());
+          transform(ThisMask, NewMask.begin(), [&SVSrc](int Mask) {
+            return SVSrc->getShuffleMask()[Mask];
+          });
+          V = Builder.CreateShuffleVector(SVSrc->getOperand(0), NewMask);
+        } else {
+          V = Builder.CreateShuffleVector(Src, ThisMask);
+        }
         propagateIRFlags(V, E->Scalars, VL0);
         if (auto *I = dyn_cast<Instruction>(V))
           V = propagateMetadata(I, E->Scalars);
diff --git a/llvm/test/Transforms/SLPVectorizer/revec-shufflevector.ll b/llvm/test/Transforms/SLPVectorizer/revec-shufflevector.ll
index 8091c218addfab..a2673d81068d8d 100644
--- a/llvm/test/Transforms/SLPVectorizer/revec-shufflevector.ll
+++ b/llvm/test/Transforms/SLPVectorizer/revec-shufflevector.ll
@@ -105,3 +105,19 @@ entry:
   store <4 x i32> %2, ptr %6, align 4
   ret void
 }
+
+define void @test5(ptr %out) {
+; CHECK-LABEL: @test5(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    store <8 x i32> zeroinitializer, ptr [[OUT:%.*]], align 4
+; CHECK-NEXT:    ret void
+;
+entry:
+  %0 = shufflevector <8 x i32> zeroinitializer, <8 x i32> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
+  %1 = shufflevector <8 x i32> zeroinitializer, <8 x i32> poison, <4 x i32> <i32 4, i32 5, i32 6, i32 7>
+  %2 = getelementptr inbounds i32, ptr %out, i64 0
+  %3 = getelementptr inbounds i32, ptr %out, i64 4
+  store <4 x i32> %0, ptr %2, align 4
+  store <4 x i32> %1, ptr %3, align 4
+  ret void
+}

[alexey-bataev]

Does it just copy the original shuffle mask for SVSrc and create a copy of SVSrc?

[HanKuanChen]

No. SVSrc has its own mask. But the current shufflevector has its own mask (from calculateShufflevectorMask(E->Scalars)) too. We are trying to blend the mask from calculateShufflevectorMask and SVSrc.