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Re: Missing guard in ira-color.c ?


On May 10, 2012, at 10:41 PM, Vladimir Makarov wrote:

> On 05/10/2012 09:10 AM, Tristan Gingold wrote:
>> Hi,
>> 
>> I am getting a segfault in ira-color.c:2945 on the trunk:
>> 
>> Program received signal SIGSEGV, Segmentation fault.
>> 0x0000000000a79f37 in move_spill_restore () at ../../src/gcc/ira-color.c:2945
>> 2945		      || ira_reg_equiv_const[regno] != NULL_RTX
>> (gdb) l
>> 2940		      /* don't do the optimization because it can create
>> 2941			 copies and the reload pass can spill the allocno set
>> 2942			 by copy although the allocno will not get memory
>> 2943			 slot.  */
>> 2944		      || ira_reg_equiv_invariant_p[regno]
>> 2945		      || ira_reg_equiv_const[regno] != NULL_RTX
>> 2946		      || !bitmap_bit_p (loop_node->border_allocnos, ALLOCNO_NUM (a)))
>> 2947		    continue;
>> 2948		  mode = ALLOCNO_MODE (a);
>> 2949		  rclass = ALLOCNO_CLASS (a);
>> 
>> while building gcc (gnatcmd.adb file) for ia64-vms using a cross compiler (target=ia64-vms, host=x86_64-linux).
>> 
>> The reason looks to be an out of bounds access:
>> 
>> (gdb) print regno
>> $10 = 18476
>> (gdb) print ira_reg_equiv_len
>> $11 = 17984
>> 
>> (I suppose this setup is not easy at all to reproduce, but I can provide any files, if necessary).
> Tristan, thanks for reporting this.
>> Wild guess, as I don't know IRA at all:  looks like in this file most accesses to ira_reg_equiv_* are guarded.  Is it expected that they aren't at this point ?
> Yes, I guess.  It is possible to have the pseudos which are out of range ira_reg_equiv_const.  It should be hard to reproduce such error because they are generated when we need to break circular dependence (e.g. when hard register 1 should be moved to hard register 2 and hard register 2 to hard register 1).
> 
> Your solution is perfectly fine.  So you can commit the patch into the trunk as pre-approved.

Now committed, after reg-testing on GNU/Linux x86_64.

Tristan.


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