[PATCH] D110869: [X86] Implement -fzero-call-used-regs option

Thu Sep 30 12:55:23 PDT 2021

nickdesaulniers requested changes to this revision.
nickdesaulniers added a comment.
This revision now requires changes to proceed.

We'll probably need to investigate code gen a little.

A mainline linux kernel defconfig built with `CONFIG_ZERO_CALL_USED_REGS=y` enabled doesn't boot, for example.  I consider that a blocker before landing this (much-appreciated) feature; marking it as such.  (Though it's possible that there are TUs in the kernel that may need to be built with `-fzero-call-used-regs=skip` that aren't (yet) failing with GCC).  I don't observe the kernel getting to `start_kernel`, which is the arch-agnostic entry point of the boot; so there's likely x86 specific C code invoked before the generic boot code takes over that may not play well with the instrumentation as implemented.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D110869/new/

https://reviews.llvm.org/D110869