[SLP]Fix createInsertVector mask emission

Author: alexey-bataev

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -4972,7 +4972,7 @@ static Value *createInsertVector(
     // the subvector length.
     const unsigned VecVF = getNumElements(Vec->getType());
     SmallVector<int> Mask(VecVF, PoisonMaskElem);
-    std::iota(Mask.begin(), std::next(Mask.begin(), Index), 0);
+    std::iota(Mask.begin(), Mask.end(), 0);
     for (unsigned I : seq<unsigned>(SubVecVF))
       Mask[I + Index] = I + VecVF;
     if (Generator) {
@@ -13976,11 +13976,12 @@ Value *BoUpSLP::gather(
     Instruction *InsElt;
     if (auto *VecTy = dyn_cast<FixedVectorType>(Scalar->getType())) {
       assert(SLPReVec && "FixedVectorType is not expected.");
-      Vec = InsElt = cast<Instruction>(createInsertVector(
-          Builder, Vec, Scalar, Pos * getNumElements(VecTy)));
-      auto *II = dyn_cast<IntrinsicInst>(InsElt);
+      Vec =
+          createInsertVector(Builder, Vec, Scalar, Pos * getNumElements(VecTy));
+      auto *II = dyn_cast<IntrinsicInst>(Vec);
       if (!II || II->getIntrinsicID() != Intrinsic::vector_insert)
         return Vec;
+      InsElt = II;
     } else {
       Vec = Builder.CreateInsertElement(Vec, Scalar, Builder.getInt32(Pos));
       InsElt = dyn_cast<InsertElementInst>(Vec);

llvm/test/Transforms/SLPVectorizer/X86/insert-subvector.ll

@@ -17,7 +17,7 @@ define <16 x double> @test(ptr %x, double %v, double %a) {
 ; CHECK-NEXT:    [[TMP9:%.*]] = shufflevector <2 x double> [[TMP8]], <2 x double> poison, <2 x i32> zeroinitializer
 ; CHECK-NEXT:    [[TMP10:%.*]] = call <16 x double> @llvm.vector.insert.v16f64.v6f64(<16 x double> poison, <6 x double> [[TMP1]], i64 0)
 ; CHECK-NEXT:    [[TMP11:%.*]] = shufflevector <4 x double> [[TMP3]], <4 x double> poison, <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison>
-; CHECK-NEXT:    [[TMP12:%.*]] = shufflevector <16 x double> [[TMP10]], <16 x double> [[TMP11]], <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 16, i32 17, i32 18, i32 19, i32 poison, i32 poison>
+; CHECK-NEXT:    [[TMP12:%.*]] = shufflevector <16 x double> [[TMP10]], <16 x double> [[TMP11]], <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 16, i32 17, i32 18, i32 19, i32 14, i32 15>
 ; CHECK-NEXT:    [[TMP13:%.*]] = call <16 x double> @llvm.vector.insert.v16f64.v2f64(<16 x double> [[TMP12]], <2 x double> [[TMP6]], i64 6)
 ; CHECK-NEXT:    [[TMP14:%.*]] = call <16 x double> @llvm.vector.insert.v16f64.v2f64(<16 x double> [[TMP13]], <2 x double> [[TMP7]], i64 8)
 ; CHECK-NEXT:    [[TMP15:%.*]] = call <16 x double> @llvm.vector.insert.v16f64.v2f64(<16 x double> [[TMP14]], <2 x double> [[TMP9]], i64 10)