[llvm] [ctxprof] Use the flattened contextual profile pre-thinlink (PR #134723)

[Snehasish Kumar via llvm-commits]

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@@ -299,20 +310,27 @@ void PGOContextualProfile::visit(ConstVisitor V, const Function *F) const {
 
 const CtxProfFlatProfile PGOContextualProfile::flatten() const {
   CtxProfFlatProfile Flat;
+  auto Accummulate = +[](SmallVectorImpl<uint64_t> &Into,
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snehasish wrote:

Do you need the `+` to cast it to a c-style function pointer? I don't see any usage which requires this.

https://github.com/llvm/llvm-project/pull/134723