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Re: [PATCH] postreload: Invalidate reg_state info@barrier/volatile insns

From: Eric Botcazou <ebotcazou at adacore dot com>
To: Andreas Krebbel <krebbel at linux dot vnet dot ibm dot com>
Cc: gcc-patches at gcc dot gnu dot org
Date: Tue, 22 Nov 2011 19:10:57 +0100
Subject: Re: [PATCH] postreload: Invalidate reg_state info@barrier/volatile insns
References: <20111114172842.GA8835@bart> <201111211312.16842.ebotcazou@adacore.com> <4ECA5078.6070006@linux.vnet.ibm.com>

> Wouldn't this prevent optimizations in cases like:
>
> insn 1: r1 = r2 + r3
> insn 2: r4 = r1, r1 dead
> insn 3: unspec_volatile
>
> With the proposal above we would mark r1 with an invalid use when passing
> insn 3. But for registers which are already dead we should not do this.

You're right.  The patch is OK, thanks for explaining.

-- 
Eric Botcazou

References:
- [PATCH] postreload: Invalidate reg_state info at barrier/volatile insns
  - From: Andreas Krebbel
- Re: [PATCH] postreload: Invalidate reg_state info@barrier/volatile insns
  - From: Eric Botcazou
- Re: [PATCH] postreload: Invalidate reg_state info@barrier/volatile insns
  - From: Andreas Krebbel

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