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From: "mikpe at it dot uu dot se" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/45034] [4.3/4.4/4.5/4.6 Regression] "safe" conversion from unsigned to signed char gives broken code Date: Sun, 25 Jul 2010 10:56:00 -0000 [thread overview] Message-ID: <20100725105606.1809.qmail@sourceware.org> (raw) In-Reply-To: <bug-45034-7665@http.gcc.gnu.org/bugzilla/> ------- Comment #6 from mikpe at it dot uu dot se 2010-07-25 10:56 ------- My bisection identified r114057 as the cause or trigger for this bug: http://gcc.gnu.org/ml/gcc-cvs/2006-05/msg00661.html The assembly code diff for the test case with r114056 and r114057 is: --- char-neg.s-r114056 2010-07-25 12:22:25.000000000 +0200 +++ char-neg.s-r114057 2010-07-25 12:22:31.000000000 +0200 @@ -57,9 +57,10 @@ movl %edi, %eax xorl %ebx, %ebx cmpb $-128, %al + movl %edi, %eax sete %bl negl %eax - movsbl %al,%eax + subl $256, %eax movl %ebx, 8(%esp) movl %eax, 4(%esp) movl %edi, (%esp) which looks completely broken. (This is the inlined code for foo() in the loop in test_neg().) r114057 was backported to 4.1.2, but for some reason the bug doesn't trigger there. -- mikpe at it dot uu dot se changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |rakdver at gcc dot gnu dot | |org Known to fail|4.3.2 |4.3.2 4.2.0 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45034
next prev parent reply other threads:[~2010-07-25 10:56 UTC|newest] Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top 2010-07-22 21:13 [Bug c/45034] New: " mikpe at it dot uu dot se 2010-07-22 21:14 ` [Bug c/45034] " mikpe at it dot uu dot se 2010-07-22 21:26 ` [Bug tree-optimization/45034] " pinskia at gcc dot gnu dot org 2010-07-23 4:14 ` hjl dot tools at gmail dot com 2010-07-23 8:52 ` [Bug tree-optimization/45034] [4.3/4.4/4.5/4.6 Regression] " rguenth at gcc dot gnu dot org 2010-07-24 18:47 ` mikpe at it dot uu dot se 2010-07-25 10:56 ` mikpe at it dot uu dot se [this message] 2010-07-26 14:47 ` rakdver at gcc dot gnu dot org 2010-07-27 22:18 ` mikpe at it dot uu dot se 2010-07-27 22:43 ` joseph at codesourcery dot com 2010-07-27 23:09 ` rakdver at kam dot mff dot cuni dot cz 2010-07-28 9:32 ` rguenth at gcc dot gnu dot org 2010-07-28 12:24 ` rguenth at gcc dot gnu dot org 2010-07-28 14:14 ` mikpe at it dot uu dot se 2010-07-28 15:38 ` mikpe at it dot uu dot se 2010-07-28 23:32 ` mikpe at it dot uu dot se 2010-07-29 11:00 ` rguenth at gcc dot gnu dot org 2010-07-29 11:00 ` [Bug tree-optimization/45034] [4.3/4.4/4.5 " rguenth at gcc dot gnu dot org 2010-08-08 15:50 ` rguenth at gcc dot gnu dot org 2010-08-08 15:51 ` [Bug tree-optimization/45034] [4.3/4.4 " rguenth at gcc dot gnu dot org
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