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From: "rguenth at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/44828] possible integer wrong code bug Date: Tue, 06 Jul 2010 10:35:00 -0000 [thread overview] Message-ID: <20100706103515.10586.qmail@sourceware.org> (raw) In-Reply-To: <bug-44828-12544@http.gcc.gnu.org/bugzilla/> ------- Comment #3 from rguenth at gcc dot gnu dot org 2010-07-06 10:35 ------- The bug is that we have in .original { return si1 * si2; } while it should have been { return (char)((unsigned char) si1 * (unsigned char) si2); } which is premature optimization by convert_to_integer, short-cutting the correctly implemented fold of (signed char)((int) si1 * (int) si2) to the above. Index: gcc/convert.c =================================================================== --- gcc/convert.c (revision 161840) +++ gcc/convert.c (working copy) @@ -774,7 +774,8 @@ convert_to_integer (tree type, tree expr || ((!TYPE_OVERFLOW_WRAPS (TREE_TYPE (arg0)) || !TYPE_OVERFLOW_WRAPS (TREE_TYPE (arg1))) && (ex_form == PLUS_EXPR - || ex_form == MINUS_EXPR))) + || ex_form == MINUS_EXPR + || ex_form == MULT_EXPR))) typex = unsigned_type_for (typex); else typex = signed_type_for (typex); fixes this. -- rguenth at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- AssignedTo|unassigned at gcc dot gnu |rguenth at gcc dot gnu dot |dot org |org Status|UNCONFIRMED |ASSIGNED Ever Confirmed|0 |1 Last reconfirmed|0000-00-00 00:00:00 |2010-07-06 10:35:15 date| | http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44828
next prev parent reply other threads:[~2010-07-06 10:35 UTC|newest] Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top 2010-07-05 22:52 [Bug c/44828] New: " regehr at cs dot utah dot edu 2010-07-06 9:25 ` [Bug c/44828] " jakub at gcc dot gnu dot org 2010-07-06 9:33 ` jakub at gcc dot gnu dot org 2010-07-06 10:35 ` rguenth at gcc dot gnu dot org [this message] 2010-07-06 13:38 ` rguenth at gcc dot gnu dot org 2010-07-06 13:41 ` [Bug c/44828] [4.3/4.4/4.5 Regression] " rguenth at gcc dot gnu dot org 2010-07-06 14:11 ` regehr at cs dot utah dot edu 2010-07-07 22:52 ` bergner at gcc dot gnu dot org 2010-07-08 4:12 ` bergner at gcc dot gnu dot org 2010-07-08 4:19 ` bergner at gcc dot gnu dot org 2010-07-08 7:47 ` jakub at gcc dot gnu dot org 2010-07-08 11:57 ` [Bug c/44828] [4.3/4.4 " rguenth at gcc dot gnu dot org 2010-07-08 11:57 ` [Bug c/44828] [4.3/4.4/4.5 " rguenth at gcc dot gnu dot org 2010-07-08 14:18 ` [Bug c/44828] [4.3/4.4 " bergner at gcc dot gnu dot org 2010-07-27 11:24 ` rguenth at gcc dot gnu dot org
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