[llvm] [PowerPC] Fix vector_shuffle combines when inputs are scalar_to_vector of differing types. (PR #80784)

[zhijian lin via llvm-commits]

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@@ -15687,16 +15687,20 @@ static SDValue isScalarToVec(SDValue Op) {
 // On little endian, that's just the corresponding element in the other
 // half of the vector. On big endian, it is in the same half but right
 // justified rather than left justified in that half.
-static void fixupShuffleMaskForPermutedSToV(SmallVectorImpl<int> &ShuffV,
-                                            int LHSMaxIdx, int RHSMinIdx,
-                                            int RHSMaxIdx, int HalfVec,
-                                            unsigned ValidLaneWidth,
-                                            const PPCSubtarget &Subtarget) {
-  for (int i = 0, e = ShuffV.size(); i < e; i++) {
-    int Idx = ShuffV[i];
-    if ((Idx >= 0 && Idx < LHSMaxIdx) || (Idx >= RHSMinIdx && Idx < RHSMaxIdx))
-      ShuffV[i] +=
-          Subtarget.isLittleEndian() ? HalfVec : HalfVec - ValidLaneWidth;
+static void fixupShuffleMaskForPermutedSToV(
+    SmallVectorImpl<int> &ShuffV, int LHSFirstElt, int LHSLastElt,
+    int RHSFirstElt, int RHSLastElt, int HalfVec, unsigned LHSNumValidElts,
+    unsigned RHSNumValidElts, const PPCSubtarget &Subtarget) {
+  int LHSEltFixup =
+      Subtarget.isLittleEndian() ? HalfVec : HalfVec - LHSNumValidElts;
+  int RHSEltFixup =
+      Subtarget.isLittleEndian() ? HalfVec : HalfVec - RHSNumValidElts;
+  for (int I = 0, E = ShuffV.size(); I < E; ++I) {
+    int Idx = ShuffV[I];
+    if (Idx >= LHSFirstElt && Idx <= LHSLastElt)
+      ShuffV[I] += LHSEltFixup;
+    if (Idx >= RHSFirstElt && Idx <= RHSLastElt)
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diggerlin wrote:

nit: change to 
  `else  if (Idx >= RHSFirstElt && Idx <= RHSLastElt)`

https://github.com/llvm/llvm-project/pull/80784