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Re: A + B CMP A -> A CMP' CST' match.pd patterns [was [PATCH] avoid calling memset et al. with excessively large sizes (PR 79095)]

From: Marc Glisse <marc dot glisse at inria dot fr>
To: Richard Biener <richard dot guenther at gmail dot com>
Cc: Jeff Law <law at redhat dot com>, Martin Sebor <msebor at gmail dot com>, Jakub Jelinek <jakub at redhat dot com>, Gcc Patch List <gcc-patches at gcc dot gnu dot org>
Date: Tue, 24 Jan 2017 15:29:27 +0100 (CET)
Subject: Re: A + B CMP A -> A CMP' CST' match.pd patterns [was [PATCH] avoid calling memset et al. with excessively large sizes (PR 79095)]
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On Tue, 24 Jan 2017, Richard Biener wrote:

That was my thought as well, but AFAICT we only call into match.pd
from VRP if we changed the insn.


Yes - there was thoughts to change that (but it comes at an expense).
Basically we'd like to re-fold stmts that indirectly use stmts we
changed.  We certainly don't want to re-fold everything all the time.


VRP is kind of a special case, every variable for which it finds a
new/improved range could be considered changed, since it may trigger
some extra transformation in match.pd (same for CCP and the nonzero
mask).

--
Marc Glisse

Follow-Ups:
- Re: A + B CMP A -> A CMP' CST' match.pd patterns [was [PATCH] avoid calling memset et al. with excessively large sizes (PR 79095)]
  - From: Jeff Law

References:
- [PATCH] avoid calling memset et al. with excessively large sizes (PR 79095)
  - From: Martin Sebor
- Re: [PATCH] avoid calling memset et al. with excessively large sizes (PR 79095)
  - From: Jakub Jelinek
- Re: [PATCH] avoid calling memset et al. with excessively large sizes (PR 79095)
  - From: Martin Sebor
- Re: [PATCH] avoid calling memset et al. with excessively large sizes (PR 79095)
  - From: Jeff Law
- Re: [PATCH] avoid calling memset et al. with excessively large sizes (PR 79095)
  - From: Jakub Jelinek
- Re: [PATCH] avoid calling memset et al. with excessively large sizes (PR 79095)
  - From: Martin Sebor
- Re: [PATCH] avoid calling memset et al. with excessively large sizes (PR 79095)
  - From: Jeff Law
- A + B CMP A -> A CMP' CST' match.pd patterns [was [PATCH] avoid calling memset et al. with excessively large sizes (PR 79095)]
  - From: Jeff Law
- Re: A + B CMP A -> A CMP' CST' match.pd patterns [was [PATCH] avoid calling memset et al. with excessively large sizes (PR 79095)]
  - From: Marc Glisse
- Re: A + B CMP A -> A CMP' CST' match.pd patterns [was [PATCH] avoid calling memset et al. with excessively large sizes (PR 79095)]
  - From: Jeff Law
- Re: A + B CMP A -> A CMP' CST' match.pd patterns [was [PATCH] avoid calling memset et al. with excessively large sizes (PR 79095)]
  - From: Richard Biener

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