Re: [x86 PATCH] PR target/106122: Don't update %esp via the stack with -Oz.

[Uros Bizjak <ubizjak@gmail.com>]

On Fri, Jul 1, 2022 at 1:00 AM Roger Sayle <roger@nextmovesoftware.com> wrote:
>
>
> When optimizing for size with -Oz, setting a register can be minimized by
> pushing an immediate value to the stack and popping it to the destination.
> Alas the one general register that shouldn't be updated via the stack is
> the stack pointer itself, where "pop %esp" can't be represented in GCC's
> RTL ("use of a register mentioned in pre_inc, pre_dec, post_inc or
> post_dec is not permitted within the same instruction").  This patch
> fixes PR target/106122 by explicitly checking for SP_REG in the
> problematic peephole2.
>
> This patch has been tested on x86_64-pc-linux-gnu with make bootstrap
> and make -k check, both with and without --target_board=unix{-m32}
> with no new failures.  Ok for mainline?
>
>
> 2022-06-30  Roger Sayle  <roger@nextmovesoftware.com>
>
> gcc/ChangeLog
>         PR target/106122
>         * config/i386/i386.md (peephole2): Avoid generating pop %esp
>         when optimizing for size.
>
> gcc/testsuite/ChangeLog
>         PR target/106122
>         * gcc.target/i386/pr106122.c: New test case.

OK for mainline and backport.

Thanks,
Uros.

>
>
> Thanks in advance,
> Roger
> --
>