[Bug rtl-optimization/49847] [4.7 Regression] NULL deref in fold_rtx (prev_insn_cc0 == NULL)

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49847

--- Comment #15 from Mikael Pettersson <mikpe at it dot uu.se> 2012-02-07 
15:48:22 UTC ---
(In reply to comment #12)
> The problem appears to be due to the exception region on a cc0 setter, which
> separates it from the cc0 consumer:
> 
> (insn 4013 4012 8164 949 (set (cc0)
>         (compare (reg:SF 912 [ D.26269 ])
>             (const_double:SF -2147483648 [0x80000000] 2.147483648e+9
> [0x0.8p+32]))) ../../../gcc/libjava/interpret.cc:131 -1
>      (expr_list:REG_EH_REGION (const_int 4 [0x4])
>         (nil)))
> 
> (note 8164 4013 4014 950 [bb 950] NOTE_INSN_BASIC_BLOCK)
> 
> (insn 4014 8164 4015 950 (set (reg:QI 2121)
>         (ge:QI (cc0)
>             (const_int 0 [0]))) ../../../gcc/libjava/interpret.cc:131 -1
>      (nil))
> 
> Happens in trunk since r180192.

r180192 contains two changes: it's the tree-eh.c change that triggers the ICE,
the other tree-ssa-forwprop.c change makes no difference to this PR.