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Re: s390: Avoid CAS boolean output inefficiency

From: Eric Botcazou <ebotcazou at adacore dot com>
To: Richard Henderson <rth at redhat dot com>
Cc: gcc-patches at gcc dot gnu dot org, Ulrich Weigand <uweigand at de dot ibm dot com>
Date: Thu, 9 Aug 2012 18:54:08 +0200
Subject: Re: s390: Avoid CAS boolean output inefficiency
References: <201208061834.q76IY8HS013445@d06av02.portsmouth.uk.ibm.com> <502047E4.50304@redhat.com>

> This was caused (or perhaps abetted by) the representation of EQ
> as NE ^ 1.  With the subsequent truncation and zero-extend, I
> think combine reached its insn limit of 3 before seeing everything
> it needed to see.

This can be 4 now, if you tweak the initial heuristic.

-- 
Eric Botcazou

References:
- Re: [PATCH 2/2] s390: Convert from sync to atomic optabs
  - From: Ulrich Weigand
- s390: Avoid CAS boolean output inefficiency
  - From: Richard Henderson

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