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From: "roger at nextmovesoftware dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/107812] [11/12/13/14 Regression] RTL SSA forwprop
 introduced regression since r11-6188
Date: Mon, 29 May 2023 16:17:13 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107812

Roger Sayle <roger at nextmovesoftware dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |roger at nextmovesoftware =
dot com

--- Comment #3 from Roger Sayle <roger at nextmovesoftware dot com> ---
Things are better but not perfect on trunk (GCC 14.0.0):
        pushl   %esi
        pushl   %ebx
        movl    16(%esp), %eax  ; y
        movl    20(%esp), %ecx  ; z
        movl    12(%esp), %edx  ; x
        movl    4(%eax), %ebx   ; y[1]
        movl    (%eax), %esi    ; y[0]
        movl    %ebx, %eax
        shrdl   %esi, %eax
        movl    %eax, (%edx)
        popl    %ebx
        popl    %esi
        ret
So the xorl and orl are gone, and we're down to two pushs/pops.
It looks like the additional spill is just a difference in register allocat=
ion.

Perhaps i386.md's *concatsidi3_3 could be cleverer (to avoid the early clob=
ber
&r when both operands are mem, and their addressing mode is sufficently
simple).
i.e.
        movl    (%eax), %esi    ; y[0]
        movl    4(%eax), %eax   ; y[1]
instead of
        movl    4(%eax), %ebx   ; y[1]
        movl    (%eax), %esi    ; y[0]
        movl    %ebx, %eax=