[PATCH] D19855: [PGO] Don't value-instrument llvm.global_ctors and llvm.global_dtors functions

[Sean Silva via llvm-commits]

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silvas added a comment.

In http://reviews.llvm.org/D19855#420069, @davidxl wrote:

> This does not work well for O0 compilation. __cxx_global_var_init also needs to be skipped, but it is not directly referenced by llvm.global_ctors.  Probably just skip functions in startup section.


I don't think that is a good solution. The name of that section is not always applied and varies from platform to platform even when it is applied (see getStaticInitSectionSpecifier in clang and its overrides; duplicating that information in this pass is undesirable).

Maybe we could do a CG walk from the `llvm.global_[cd]tors` functions or something? A naive walk is probably not sufficient (would find too many things). But maybe functions used transitively by `llvm.global_[cd]tors` and that is the only use?


http://reviews.llvm.org/D19855