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[Bug tree-optimization/69984] [4.9/5/6] Signed comparison instruction emitted for unsigned variable comparison
- From: "jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Mon, 29 Feb 2016 17:23:36 +0000
- Subject: [Bug tree-optimization/69984] [4.9/5/6] Signed comparison instruction emitted for unsigned variable comparison
- Auto-submitted: auto-generated
- References: <bug-69984-4 at http dot gcc dot gnu dot org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69984
--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Even if the computation is 32-bit, by the time you multiply say (unsigned short
int) 0xffff with itself, you get undefined behavior.
So, as has been said, if you want to perform the multiplication in unsigned
long or unsigned int, you need to cast one of the operands.