[llvm] [LV] Use SCEVPatternMatch to improve code (NFC) (PR #154568)

[Florian Hahn via llvm-commits]

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@@ -107,14 +107,25 @@ struct specificscev_ty {
 /// Match if we have a specific specified SCEV.
 inline specificscev_ty m_scev_Specific(const SCEV *S) { return S; }
 
-struct is_specific_cst {
-  uint64_t CV;
-  is_specific_cst(uint64_t C) : CV(C) {}
-  bool isValue(const APInt &C) const { return C == CV; }
+template <typename ITy> struct is_specific_cst {
+  ITy CV;
+  is_specific_cst(ITy C) : CV(C) {}
+  bool isValue(const APInt &C) const {
+    if constexpr (std::is_unsigned_v<ITy>)
+      return C.tryZExtValue() == CV;
+    return C.trySExtValue() == CV;
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fhahn wrote:

Could we leave `m_scev_SpecificInt` as-is, and just add a seperate matcher that makes clear we are matching the sign-extended value?

https://github.com/llvm/llvm-project/pull/154568