[clang] [Clang][RVV][SVE] Cache getScalableVectorType lookups (PR #160108)

[Paul Walker via cfe-commits]

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@@ -4567,6 +4567,11 @@ QualType ASTContext::getWebAssemblyExternrefType() const {
 /// type.
 QualType ASTContext::getScalableVectorType(QualType EltTy, unsigned NumElts,
                                            unsigned NumFields) const {
+  auto K = llvm::ScalableVecTyKey{
+      reinterpret_cast<uintptr_t>(EltTy.getAsOpaquePtr()), NumElts, NumFields};
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paulwalker-arm wrote:

My knowledge here is not great, is it safe to assume the opaque ptr is unique? Why not use QualType directly.  I can see this done in other places (e.g. NullableQualTypeDenseMapInfo).

https://github.com/llvm/llvm-project/pull/160108