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Re: [PATCH] Avoid introducing TREE_OVERFLOWs in (T)(x&cst) -> (T)x & (T)cst optimization (PR middle-end/19857)
- From: kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)
- To: ebotcazou at libertysurf dot fr
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Tue, 15 Feb 05 16:11:45 EST
- Subject: Re: [PATCH] Avoid introducing TREE_OVERFLOWs in (T)(x&cst) -> (T)x & (T)cst optimization (PR middle-end/19857)
Sorry if this has already been mentioned, but I think your patch might
be harmful to the Ada compiler, at least without specific
counter-measures. My understanding is that gigi relies on
TREE_OVERFLOW being set by fold to issue warnings and detect
CONSTRAINT_ERRORs at compile-time. And, in some cases, that's vital
(from Ada's viewpoint) because things would wrap around in the
target's arithmetics, hence would go unnoticed at run-time.
I agree with you and have said that before. I was assured there'd be no
changed in the visible handling of TREE_OVERFLOW.