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Re: Ping^3 : [PATCH] [gcc, combine] PR46164: Don't combine the insns if a volatile register is contained.

On Wed, Apr 22, 2015 at 9:44 AM, Segher Boessenkool
<> wrote:
> On Tue, Apr 21, 2015 at 03:13:38PM +0800, Terry Guo wrote:
>> > Did you fix the comment?  REG_USERVAR_P and HARD_REGISTER_P can be
>> > set for more than just register asm.
>> Sorry for missing the patch. I believe that I addressed your patch.
>> Please review it again to make sure my understanding is correct.
>> +  /* Use REG_USERVAR_P and HARD_REGISTER_P to check whether DEST is a user
>> +     specified register, and do not eliminate such register if it is in an
>> +     asm input.  Otherwise if allow such elimination, we may break the
>> +     register asm usage defined in GCC manual.  */
>> +  if (REG_P (dest) && REG_USERVAR_P (dest) && HARD_REGISTER_P (dest)
>> +      && extract_asm_operands (PATTERN (i3)))
>> +    return 0;
> The "to check whether DEST is a user-specified register" part is not
> correct; this check can for example also match for function arguments
> (which are hard regs) that were combined into any "normal" user var.
> I don't see how we would do a better check, and disallowing combination
> in this case is harmless (or even good); but the comment is misleading.
> Segher

Thanks for reviewing. Patch is updated per you suggestion. The
ChangeLog is also updated as below:

2015-04-22 Hale Wang <>
                    Terry Guo  <>

       PR rtl-optimization/64818
       * combine.c (can_combine_p): Don't combine user-specified register if
       it is in an asm input.

2015-04-22 Hale Wang <>
                    Terry Guo  <>

       PR rtl-optimization/64818
       * New.

Attachment: pr64818-combine-user-specified-register-v6.txt
Description: Text document

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