On Thu, Mar 5, 2026 at 9:50 AM Jakub Jelinek <[email protected]> wrote:
>
> Hi!
>
> While in this case it is not an assemble failure nor wrong-code,
> because say xchgl %eax, %edx and xchg eax, edx do the same thing,
> they are encoded differently, so if we want consistency between
> -masm=att and -masm=intel emitted code (my understanding is that
> is what is Zdenek testing right now, fuzzing code, compiling
> with both -masm=att and -masm=intel and making sure if the former
> assembles, the latter does too and they result in identical
> *.o files), we should use different order of the operands
> even here (and it doesn't matter which order we pick).
Makes a lot of sense in this regard.
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> I've grepped the *.md files with
> grep '\\t%[0-9], %[0-9]' *.md | grep -v '%0, %0'
> i386.md: "xchg{<imodesuffix>}\t%1, %0"
> i386.md: xchg{<imodesuffix>}\t%1, %0
> i386.md: "wrss<mskmodesuffix>\t%0, %1"
> i386.md: "wruss<mskmodesuffix>\t%0, %1"
> (before this and PR124366 fix) and later on also with
> grep '\\t%[a-z0-9_<>]*[0-9], %[a-z0-9_<>]*[0-9]' *.md | grep -v '%0, %0'
> and checked all the output and haven't found anything else problematic.
>
> 2026-03-05 Jakub Jelinek <[email protected]>
>
> * config/i386/i386.md (swap<mode>): Swap operand order for
> -masm=intel.
OK.
Thanks,
Uros.
> --- gcc/config/i386/i386.md.jj 2026-03-03 15:47:04.230275241 +0100
> +++ gcc/config/i386/i386.md 2026-03-04 21:52:33.409720768 +0100
> @@ -3360,7 +3360,7 @@ (define_insn "swap<mode>"
> (set (match_dup 1)
> (match_dup 0))]
> ""
> - "xchg{<imodesuffix>}\t%1, %0"
> + "xchg{<imodesuffix>}\t{%1, %0|%0, %1}"
> [(set_attr "type" "imov")
> (set_attr "mode" "<MODE>")
> (set_attr "pent_pair" "np")
> @@ -3375,8 +3375,8 @@ (define_insn "*swap<mode>"
> (match_dup 0))]
> ""
> "@
> - xchg{<imodesuffix>}\t%1, %0
> - xchg{l}\t%k1, %k0"
> + xchg{<imodesuffix>}\t{%1, %0|%0, %1}
> + xchg{l}\t{%k1, %k0|%k0, %k1}"
> [(set_attr "type" "imov")
> (set_attr "mode" "<MODE>,SI")
> (set (attr "preferred_for_size")
>
> Jakub
>
