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

From: Terry Guo <flameroc at gmail dot com>
To: Segher Boessenkool <segher at kernel dot crashing dot org>
Cc: richard dot sandiford at arm dot com, rdsandiford at googlemail dot com, GCC Patches <gcc-patches at gcc dot gnu dot org>, Hale Wang <hale dot wang at arm dot com>
Date: Tue, 17 Feb 2015 11:39:34 +0800
Subject: Re: Ping : [PATCH] [gcc, combine] PR46164: Don't combine the insns if a volatile register is contained.
Authentication-results: sourceware.org; auth=none
References: <002701d04409$a20efcb0$e62cf610$ at arm dot com> <87pp9fcehe dot fsf at e105548-lin dot cambridge dot arm dot com> <20150212221552 dot GA25883 at gate dot crashing dot org> <87zj8imb7x dot fsf at googlemail dot com> <CAGbRaL6872aHRCwrc28nF5RG-zSAGqza0CjurD+XjT2XVsZMBA at mail dot gmail dot com> <20150215113505 dot GA11983 at gate dot crashing dot org>

On Sun, Feb 15, 2015 at 7:35 PM, Segher Boessenkool
<segher@kernel.crashing.org> wrote:
> Hi Terry,
>
> I still think this is stage1 material.
>
>> +  /* Don't combine if dest contains a user specified register and i3 contains
>> +     ASM_OPERANDS, because the user specified register (same with dest) in i3
>> +     would be replaced by the src of insn which might be different with
>> +     the user's expectation.  */
>
> "Do not eliminate a register asm in an asm input" or similar?  Text
> explaining why REG_USERVAR_P && HARD_REGISTER_P works here would be
> good to have, too.
>
>> +  if (REG_P (dest) && REG_USERVAR_P (dest) && HARD_REGISTER_P (dest)
>> +      && (GET_CODE (PATTERN (i3)) == SET
>> +       && GET_CODE (SET_SRC (PATTERN (i3))) == ASM_OPERANDS))
>> +    return 0;
>
> That works only for asms with exactly one output.  You want
> extract_asm_operands.
>
>
> Segher

Thanks Segher. Patch is updated per you suggestion. Is this one ok for stage 1?

BR,
Terry

Attachment: pr64818-combine-user-specified-register.patch-4
Description: Binary data

Follow-Ups:
- Re: Ping : [PATCH] [gcc, combine] PR46164: Don't combine the insns if a volatile register is contained.
  - From: Segher Boessenkool

References:
- Ping : [PATCH] [gcc, combine] PR46164: Don't combine the insns if a volatile register is contained.
  - From: Hale Wang
- Re: Ping : [PATCH] [gcc, combine] PR46164: Don't combine the insns if a volatile register is contained.
  - From: Richard Sandiford
- Re: Ping : [PATCH] [gcc, combine] PR46164: Don't combine the insns if a volatile register is contained.
  - From: Segher Boessenkool
- Re: Ping : [PATCH] [gcc, combine] PR46164: Don't combine the insns if a volatile register is contained.
  - From: Richard Sandiford
- Re: Ping : [PATCH] [gcc, combine] PR46164: Don't combine the insns if a volatile register is contained.
  - From: Terry Guo
- Re: Ping : [PATCH] [gcc, combine] PR46164: Don't combine the insns if a volatile register is contained.
  - From: Segher Boessenkool

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