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[Bug c/54027] possible mis-optimization of signed left shift in c89 mode
- From: "rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Thu, 19 Jul 2012 10:07:11 +0000
- Subject: [Bug c/54027] possible mis-optimization of signed left shift in c89 mode
- Auto-submitted: auto-generated
- References: <bug-54027-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54027
--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-07-19 10:07:11 UTC ---
Isn't it invoking undefined behavior by means of a signed integer overflow?
(if shifts are not defined in terms of multiplies we may not internally
fold x << 1 to x * 2).