[SLP][REVEC] Use VL.front()->getType() as ScalarTy. (#102437)

VL.front()->getType() may be FixedVectorType when revec is enabled.

Fix "Expected item in MinBWs.".

Author: HanKuanChen

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -12586,8 +12586,15 @@ Value *BoUpSLP::vectorizeOperand(TreeEntry *E, unsigned NodeIdx,
     }
     if (IsSameVE) {
       auto FinalShuffle = [&](Value *V, ArrayRef<int> Mask) {
+        // V may be affected by MinBWs.
+        // We want ShuffleInstructionBuilder to correctly support REVEC. The key
+        // factor is the number of elements, not their type.
+        Type *ScalarTy = cast<VectorType>(V->getType())->getElementType();
+        unsigned NumElements = getNumElements(VL.front()->getType());
         ShuffleInstructionBuilder ShuffleBuilder(
-            cast<VectorType>(V->getType())->getElementType(), Builder, *this);
+            NumElements != 1 ? FixedVectorType::get(ScalarTy, NumElements)
+                             : ScalarTy,
+            Builder, *this);
         ShuffleBuilder.add(V, Mask);
         return ShuffleBuilder.finalize(std::nullopt);
       };

llvm/test/Transforms/SLPVectorizer/revec.ll

@@ -238,3 +238,37 @@ define void @test7() {
   store <8 x i16> %3, ptr null, align 2
   ret void
 }
+
+define void @test8() {
+; CHECK-LABEL: @test8(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = call <8 x float> @llvm.vector.insert.v8f32.v2f32(<8 x float> poison, <2 x float> zeroinitializer, i64 0)
+; CHECK-NEXT:    [[TMP1:%.*]] = call <8 x float> @llvm.vector.insert.v8f32.v2f32(<8 x float> [[TMP0]], <2 x float> zeroinitializer, i64 2)
+; CHECK-NEXT:    [[TMP2:%.*]] = call <8 x float> @llvm.vector.insert.v8f32.v2f32(<8 x float> [[TMP1]], <2 x float> zeroinitializer, i64 4)
+; CHECK-NEXT:    [[TMP3:%.*]] = call <8 x float> @llvm.vector.insert.v8f32.v2f32(<8 x float> [[TMP2]], <2 x float> zeroinitializer, i64 6)
+; CHECK-NEXT:    [[TMP4:%.*]] = call <4 x float> @llvm.vector.insert.v4f32.v2f32(<4 x float> poison, <2 x float> zeroinitializer, i64 0)
+; CHECK-NEXT:    [[TMP5:%.*]] = call <4 x float> @llvm.vector.insert.v4f32.v2f32(<4 x float> [[TMP4]], <2 x float> zeroinitializer, i64 2)
+; CHECK-NEXT:    br i1 false, label [[FOR0:%.*]], label [[FOR_BODY:%.*]]
+; CHECK:       for0:
+; CHECK-NEXT:    [[TMP6:%.*]] = phi <8 x float> [ [[TMP3]], [[ENTRY:%.*]] ], [ [[TMP8:%.*]], [[FOR_BODY]] ]
+; CHECK-NEXT:    ret void
+; CHECK:       for.body:
+; CHECK-NEXT:    [[TMP7:%.*]] = phi <4 x float> [ [[TMP7]], [[FOR_BODY]] ], [ [[TMP5]], [[ENTRY]] ]
+; CHECK-NEXT:    [[TMP8]] = shufflevector <4 x float> [[TMP7]], <4 x float> poison, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 0, i32 1, i32 2, i32 3>
+; CHECK-NEXT:    br i1 false, label [[FOR0]], label [[FOR_BODY]]
+;
+entry:
+  br i1 false, label %for0, label %for.body
+
+for0:
+  %0 = phi <2 x float> [ zeroinitializer, %entry ], [ %4, %for.body ]
+  %1 = phi <2 x float> [ zeroinitializer, %entry ], [ %5, %for.body ]
+  %2 = phi <2 x float> [ zeroinitializer, %entry ], [ %4, %for.body ]
+  %3 = phi <2 x float> [ zeroinitializer, %entry ], [ %5, %for.body ]
+  ret void
+
+for.body:
+  %4 = phi <2 x float> [ %4, %for.body ], [ zeroinitializer, %entry ]
+  %5 = phi <2 x float> [ %5, %for.body ], [ zeroinitializer, %entry ]
+  br i1 false, label %for0, label %for.body
+}