[PATCH] D74698: [CodeGen] -pg shouldn't add "frame-pointer"="all" fn attr w/ -mfentry

[Fangrui Song via Phabricator via cfe-commits]

MaskRay added a comment.

When -mfentry is specified, why should frame pointers be disabled? Is that because the Linux kernel has assumption about the exact code sequence? `call __fentry__` is the first instruction. Isn't that sufficient?

(There is another difference. GCC emits `call *__fentry__ at GOTPCREL(%rip)` in -fpie/-fpic mode. At first glance, this looks suboptimal to me. I don't expect `__fentry__` to be interposed.)
(This may be another example demonstrating that piggybacking an option (-mfentry) on top of an existing one (-pg) can turn out to be a bad idea...)


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  https://reviews.llvm.org/D74698/new/

https://reviews.llvm.org/D74698