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Re: [PATCH][4.3] Deprecate -ftrapv

From: Paolo Bonzini <bonzini at gnu dot org>
To: gcc-patches at gcc dot gnu dot org
Cc: gcc at gcc dot gnu dot org
Date: Sat, 01 Mar 2008 14:57:50 +0100
Subject: Re: [PATCH][4.3] Deprecate -ftrapv
References: <Pine.LNX.4.64.0803010041110.4133@zhemvz.fhfr.qr> <47C89DB1.6030200@codesourcery.com> <10803010013.AA29088@vlsi1.ultra.nyu.edu> <47C8B9D4.1000906@adacore.com> <Pine.LNX.4.64.0803010210150.23648@digraph.polyomino.org.uk> <47C8C060.70503@adacore.com> <Pine.LNX.4.64.0803011310290.26609@digraph.polyomino.org.uk>

Well presumably one would want to use target dependent stuff for
detecting overflow where it exists (sticky overflow bits on
power, O flag on PC, trapping add on MIPS etc).
On the whole I think you'd want to benefit from tree-ssa optimizing overflow checks where possible (including optimizing them away with VRP), if you hope for a -ftrapv that could be turned on by default for Ada with performance impact as small as possible. That would suggest back ends matching overflow-check patterns and converting them into such instructions.

Yes, fully fully agreed.

Paolo

References:
- Re: [PATCH][4.3] Deprecate -ftrapv
  - From: Mark Mitchell
- Re: [PATCH][4.3] Deprecate -ftrapv
  - From: Richard Kenner
- Re: [PATCH][4.3] Deprecate -ftrapv
  - From: Robert Dewar
- Re: [PATCH][4.3] Deprecate -ftrapv
  - From: Joseph S. Myers
- Re: [PATCH][4.3] Deprecate -ftrapv
  - From: Robert Dewar
- Re: [PATCH][4.3] Deprecate -ftrapv
  - From: Joseph S. Myers

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