From: Paolo Bonzini <paolo.bonzini@lu.unisi.ch>
To: Leehod Baruch <LEEHOD@il.ibm.com>, GCC Development <gcc@gcc.gnu.org>
Subject: Re: Question about merging two instructions.
Date: Mon, 22 Aug 2005 13:37:00 -0000 [thread overview]
Message-ID: <4309D517.7040106@lu.unisi.ch> (raw)
In-Reply-To: <OFA172C2D5.7846BC73-ONC2257065.00497D7B-C2257065.004A8FF3@il.ibm.com>
>Do I always need to recognize the result?
>
>
validate_change and apply_change_group will take care of that.
>If the answer is yes, than I suppose that if something bad happens,
>the recognition will fail.
>
>
No, the problem is when recognition passes, and you have a SUBREG on the
LHS that will only modify part of the pseudo. I can't think off the top
of mind of a case, but I'd rather err on the side of safety.
It may still make sense changing the default case of
simplify_replace_rtx to invoke replace_rtx rather than returning x. But
this is unrelated, because nobody is currently passing a SET to
simplify_replace_rtx (only expressions), and you should do the same:
*you* said you want to replace on the RHS, so you really want to invoke
simplify_replace_rtx on the RHS.
Paolo
next prev parent reply other threads:[~2005-08-22 13:37 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-08-21 13:52 Leehod Baruch
2005-08-21 16:55 ` Roger Sayle
2005-08-21 17:54 ` Leehod Baruch
2005-08-22 7:38 ` Paolo Bonzini
2005-08-22 13:33 ` Leehod Baruch
2005-08-22 13:37 ` Paolo Bonzini [this message]
2005-08-22 16:30 ` Richard Henderson
2005-08-22 13:49 ` Roger Sayle
2005-08-22 7:10 ` Paolo Bonzini
2005-08-22 14:12 ` Leehod Baruch
2005-08-22 14:42 ` Paolo Bonzini
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