[PATCH] D126137: [X86] Add support for `-mharden-sls=all`

Mon May 23 01:24:52 PDT 2022

kristof.beyls added a comment.

See https://gcc.gnu.org/onlinedocs/gcc/AArch64-Options.html, documentation for "mharden-sls": For AArch64, the options available on the command line are "retbr", "blr", "none" and "all".
I don't think the options necessarily have to be the same for x86.
But assuming I understand this patch correctly, it seems to me that with this patch -mharden-sls=all would mean fundamentally slightly different things for x86 vs arm and aarch64, which could be confusing to users.
IIUC this patch correctly, this patch implements the equivalent of aarch64/arm's -mharden-sls=retbr (i.e. add a straight-line-speculation mitigation for returns and indirect jumps, but not for indirect function calls).
Therefore, I wonder if it wouldn't be better to name this -mharden-sls=retbr for more consistency across architectures?
Or is the indirect function call case not relevant for x86 (sorry - I'm not up to speed on the details on the x86 side)?

Or does `MBB.back().getDesc().isIndirectBranch()` also return True for indirect calls, in which case my whole remark here can probably be ignored?

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D126137/new/

https://reviews.llvm.org/D126137