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Re: Fix twolf -funroll-loops -O3 miscompilation (a semi-latent web.c bug)

From: Eric Botcazou <ebotcazou at adacore dot com>
To: Steven Bosscher <stevenb dot gcc at gmail dot com>
Cc: gcc-patches at gcc dot gnu dot org, Paolo Bonzini <bonzini at gnu dot org>, Dominique Dhumieres <dominiq at lps dot ens dot fr>, hubicka at ucw dot cz, Richard Henderson <rth at redhat dot com>, Jeff Law <law at redhat dot com>
Date: Wed, 28 Nov 2012 00:47:41 +0100
Subject: Re: Fix twolf -funroll-loops -O3 miscompilation (a semi-latent web.c bug)
References: <20121118231540.726263BABA@mailhost.lps.ens.fr> <34723155.BbVgJcJOVM@polaris> <CABu31nM9+0Uf7BUkFxKGHmhdzK9jPx+zayDFU-=3+WRzhTyFCg@mail.gmail.com>

> Count me in, too.  So let's avoid it:
> 
>         * gcse.c (struct reg_use): Remove unused struct.
>         (gcse_emit_move_after): Do not create REG_EQUAL notes that reference
> the SET_DEST of the instruction the note would be attached to.

OK (with PR rtl-optimization/55006) if it passes bootstrap & regtest, thanks.

> And perhaps a bit in emit-rtl.c for good measure? I'll see if/where
> this causes breakage...

I think this would need to be wrapped in a #ifdef ENABLE_CHECKING/#endif pair.

-- 
Eric Botcazou

Follow-Ups:
- Re: Fix twolf -funroll-loops -O3 miscompilation (a semi-latent web.c bug)
  - From: Steven Bosscher

References:
- Re: Fix twolf -funroll-loops -O3 miscompilation (a semi-latent web.c bug)
  - From: Dominique Dhumieres
- Re: Fix twolf -funroll-loops -O3 miscompilation (a semi-latent web.c bug)
  - From: Eric Botcazou
- Re: Fix twolf -funroll-loops -O3 miscompilation (a semi-latent web.c bug)
  - From: Steven Bosscher

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