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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug rtl-optimization/57131] [4.8/4.9 Regression] Wrong register assignment?
Date: Wed, 01 May 2013 07:39:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57131

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |vmakarov at gcc dot gnu.org

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-05-01 07:39:41 UTC ---
Apparently went away with the http://gcc.gnu.org/r198432 fix, but it isn't
clear whether that change was meant to fix this or just made the bug latent.
Anyway, still reproduceable on the 4.8 branch.
What I'm seeing before that change is that extendsidi2_1 pattern with MEM
destination LRA chooses %ebx as (clobber (scratch:SI)) register, eventhough
%ebx
is live across that instruction (there is
(insn 14 74 68 2 (set (reg:SI 3 bx [orig:83 D.1395 ] [83])
        (mem/v/c:SI (plus:SI (reg/f:SI 7 sp)
                (const_int 72 [0x48])) [0 x4+0 S4 A64])) pr57131.c:11 85
{*movsi_internal}
     (nil))
(insn 68 14 73 2 (set (reg:SI 3 bx [orig:83 D.1395 ] [83])
        (reg:SI 3 bx [orig:83 D.1395 ] [83])) pr57131.c:11 85 {*movsi_internal}
     (expr_list:REG_DEAD (reg:SI 3 bx [orig:83 D.1395 ] [83])
        (nil)))
some insns before it and:
(insn 65 24 26 2 (set (reg:SI 5 di [orig:83 D.1395 ] [83])
        (reg:SI 3 bx [orig:83 D.1395 ] [83])) pr57131.c:11 85 {*movsi_internal}
     (expr_list:REG_DEAD (reg:SI 3 bx [orig:83 D.1395 ] [83])
        (nil)))
some insns after it.  Not sure if the noop move with REG_DEAD has anything to
do with that.  Vlad, can you please have a look?