Re: [PATCH v9] pgo: add clang's Profile Guided Optimization infrastructure
From: Nick Desaulniers <hidden>
Date: 2021-06-14 20:50:45
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linux-doc, linux-toolchains, lkml
On Mon, Jun 14, 2021 at 11:07 AM Nick Desaulniers [off-list ref] wrote:
On Mon, Jun 14, 2021 at 9:23 AM Kees Cook [off-list ref] wrote:quoted
On Mon, Jun 14, 2021 at 05:35:45PM +0200, Peter Zijlstra wrote:quoted
On Mon, Jun 14, 2021 at 08:26:01AM -0700, Kees Cook wrote:quoted
So, AFAICT, the original blocking issue ("PGO does not respect noinstr") is not actually an issue (noinstr contains notrace, which IS respected by PGO[2]), I think this is fine to move forward.It is *NOT*: https://godbolt.org/z/9c7xdvGd9 Look at how both compilers generate instrumentation in the no_instr() function.Well that's disappointing. I'll put this on hold until Clang can grow an appropriate attribute (or similar work-around). Thanks for catching that.Cross referencing since these two threads are related. https://lore.kernel.org/lkml/CAKwvOdmPTi93n2L0_yQkrzLdmpxzrOR7zggSzonyaw2PGshApw@mail.gmail.com/ (local)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80223 looked appropriate to me, so I commented on it. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80223#c6 Patches for: PGO: https://reviews.llvm.org/D104253 GCOV: https://reviews.llvm.org/D104257 -- Thanks, ~Nick Desaulniers