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From: "ubizjak at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/114591] [12/13/14 Regression] register allocators
 introduce an extra load operation since gcc-12
Date: Wed, 10 Apr 2024 09:07:12 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114591

--- Comment #10 from Uro=C5=A1 Bizjak <ubizjak at gmail dot com> ---
(In reply to Hongtao Liu from comment #5)
> > My experience is memory cost for the operand with rm or separate r, m is
> > different which impacts RA decision.
> >=20
> > https://gcc.gnu.org/pipermail/gcc-patches/2022-May/595573.html
>=20
> Change operands[1] alternative 2 from m -> rm, then RA makes perfect
> decision.

Yes, I can confirm this oddity:

        movl    v1(%rip), %edx  # 5     [c=3D6 l=3D6]  *zero_extendsidi2/3
        movq    %rdx, v2(%rip)  # 16    [c=3D4 l=3D7]  *movdi_internal/5
        movq    %rdx, %rax      # 18    [c=3D4 l=3D3]  *movdi_internal/3
        ret             # 21    [c=3D0 l=3D1]  simple_return_internal

But even there is room for improvement. The last move can be eliminated by
allocating %eax in the first instruction.=