[Bug rtl-optimization/47166] [4.5 4.6 Regression] SpecCpu2000 Ammp segfaults for ARM with -O3 -mthumb

[ibolton at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47166

Ian Bolton <ibolton at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2011.01.05 16:45:57
     Ever Confirmed|0                           |1

--- Comment #7 from Ian Bolton <ibolton at gcc dot gnu.org> 2011-01-05 16:45:57 UTC ---
I have altered the source, so that I call both refers_to_regno_p and
reg_mentioned_p and print out when the two disagree.  For the attached rectmm.i
input file, there are only 5 disagreements:

mismatch for regno=2343: refersto=F,mentions=T
reg = (reg/f:SI 2343)
i1 = (insn 3162 1730 3165 99 rectmm.c:1041 (set (reg/f:SI 2343)
        (reg:SI 1 r1)) -1 (nil))

mismatch for regno=2355: refersto=F,mentions=T
reg = (reg/f:SI 2355)
i1 = (insn 3166 1745 3169 99 rectmm.c:1043 (set (reg/f:SI 2355)
        (reg:SI 9 r9)) -1 (nil))

mismatch for regno=2377: refersto=F,mentions=T
reg = (reg/f:SI 2377)
i1 = (insn 3170 1770 1731 99 rectmm.c:1045 (set (reg/f:SI 2377)
        (reg:SI 12 ip)) -1 (nil))

mismatch for regno=2349: refersto=F,mentions=T
reg = (reg/f:SI 2349)
i1 = (insn 3174 1737 3177 99 rectmm.c:1042 (set (reg/f:SI 2349)
        (reg:SI 0 r0)) -1 (nil))

mismatch for regno=2361: refersto=F,mentions=T - reg and i1 follow ...
reg = (reg/f:SI 2361)
il = (insn 3178 1752 1772 99 rectmm.c:1044 (set (reg/f:SI 2361)
        (reg:SI 3 r3)) -1 (nil))

This occurs because reg_mentioned_p looks at output regs, but refers_to_regno_p
does not.

The knock-on effect of this difference must lead to those increments being
lost, but I don't know why yet.