[llvm] [X86] Fix duplicated compute in recursive search. (PR #130226)

[Phoebe Wang via llvm-commits]

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@@ -44745,31 +44746,59 @@ bool X86TargetLowering::isSplatValueForTargetNode(SDValue Op,
 
 // Helper to peek through bitops/trunc/setcc to determine size of source vector.
 // Allows combineBitcastvxi1 to determine what size vector generated a <X x i1>.
-static bool checkBitcastSrcVectorSize(SDValue Src, unsigned Size,
-                                      bool AllowTruncate) {
+static bool
+checkBitcastSrcVectorSize(SDValue Src, unsigned Size, bool AllowTruncate,
+                          std::map<std::tuple<SDValue, unsigned, bool>, bool>
+                              &BitcastSrcVectorSizeMap) {
+  auto Tp = std::make_tuple(Src, Size, AllowTruncate);
+  if (BitcastSrcVectorSizeMap.count(Tp))
+    return BitcastSrcVectorSizeMap[Tp];
   switch (Src.getOpcode()) {
   case ISD::TRUNCATE:
-    if (!AllowTruncate)
+    if (!AllowTruncate) {
+      BitcastSrcVectorSizeMap[Tp] = false;
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phoebewang wrote:

How about define a `bool Result = false;` to avoid repeat `BitcastSrcVectorSizeMap[Tp] =`?

https://github.com/llvm/llvm-project/pull/130226