fix wrong boundary check

Author: ParkHanbum

llvm/lib/Transforms/Vectorize/VectorCombine.cpp

@@ -689,7 +689,8 @@ bool VectorCombine::foldInsExtFNeg(Instruction &I) {
   // one element
   unsigned NumDstElts = DstVecTy->getNumElements();
   unsigned NumSrcElts = SrcVecTy->getNumElements();
-  if (InsIdx >= NumDstElts || ExtIdx >= NumSrcElts || NumDstElts == 1)
+  if (ExtIdx > NumSrcElts || InsIdx >= NumDstElts ||
+      NumDstElts == 1)
     return false;
 
   // We are inserting the negated element into the same lane that we extracted

llvm/test/Transforms/VectorCombine/X86/extract-fneg-insert.ll

@@ -47,9 +47,9 @@ define <4 x float> @ext2_v4f32(<4 x float> %x, <4 x float> %y) {
 
 define <4 x float> @ext2_v2f32v4f32(<2 x float> %x, <4 x float> %y) {
 ; CHECK-LABEL: @ext2_v2f32v4f32(
-; CHECK-NEXT:    [[E:%.*]] = extractelement <2 x float> [[X:%.*]], i32 2
-; CHECK-NEXT:    [[N:%.*]] = fneg float [[E]]
-; CHECK-NEXT:    [[R:%.*]] = insertelement <4 x float> [[Y:%.*]], float [[N]], i32 2
+; CHECK-NEXT:    [[TMP1:%.*]] = fneg <2 x float> [[X:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = shufflevector <2 x float> [[TMP1]], <2 x float> poison, <4 x i32> <i32 poison, i32 poison, i32 2, i32 poison>
+; CHECK-NEXT:    [[R:%.*]] = shufflevector <4 x float> [[Y:%.*]], <4 x float> [[TMP2]], <4 x i32> <i32 0, i32 1, i32 6, i32 3>
 ; CHECK-NEXT:    ret <4 x float> [[R]]
 ;
   %e = extractelement <2 x float> %x, i32 2