[Bug rtl-optimization/50078] [4.6/4.7 Regression] combine wrong code: volatile accesses optimized out

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50078

--- Comment #8 from Steven Bosscher <steven at gcc dot gnu.org> 2011-09-11 
15:47:21 UTC ---
(In reply to comment #7)
> Comes from SSA expand => Matz

Comes from SSA expand because it is already wrong in the .expand dump:
;; MEM[(volatile unsigned int *)&var][arg_1(D)] ={v} v_2;

(insn 9 8 10 (set (reg:DI 63)
        (sign_extend:DI (reg/v:SI 60 [ argD.1604 ]))) t.c:6 -1
     (nil))

(insn 10 9 11 (set (reg/f:DI 64)
        (symbol_ref:DI ("var") <var_decl 0x7f4b8054f140 var>)) t.c:6 -1
     (nil))

(insn 11 10 0 (set (mem/s:SI (plus:DI (mult:DI (reg:DI 63)
                    (const_int 4 [0x4]))
                (reg/f:DI 64)) [2 varD.1603 S4 A32])
        (reg/v:SI 59 [ vD.1607 ])) t.c:6 -1
     (nil))

It seems to me that the MEM in insn 11 should be mem/s/v.