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Re: [PATCH][4.3] Deprecate -ftrapv
- From: Robert Dewar <dewar at adacore dot com>
- To: Joern Rennecke <amylaar at spamcop dot net>
- Cc: gcc at gcc dot gnu dot org, joseph at codesourcery dot com
- Date: Sat, 01 Mar 2008 09:34:57 -0500
- Subject: Re: [PATCH][4.3] Deprecate -ftrapv
- References: <20080301092121.8tqvd8tzi8k4o0sc@webmail.spamcop.net>
Joern Rennecke wrote:
Considering the trouble that you get when you try to generate branches in
a non-branch expander, we should probably have alternate named patterns
to be used in ports to processors that have no conditional trap facility,
or where a conditional trap is more expensive than a well predictable
conditional branch.
Note that even if this is the case (conditional trap more expensive), it
may be appropriate in -Os mode. A one-byte INTO instruction after every
add takes less space than conditional jump to trapping code. Of course
it is always interesting that less code = less i-cache pressure, and
so you get something back for that in practice, YMMV.