Bug#491653: gcc-4.3: misoptimization of 64-bit bitfield when not byte aligned

2008-07-21 Thread Nick Lewycky
close 491653 thanks Hi Bastian, You're right again, this is entirely due to the effects of strict aliasing rules. The problem goes away with -fno-strict-aliasing. Nick Bastian Blank wrote: On Sun, Jul 20, 2008 at 11:14:10PM -0700, Nick Lewycky wrote: This testcase produces different output

Bug#491653: gcc-4.3: misoptimization of 64-bit bitfield when not byte aligned

2008-07-21 Thread Bastian Blank
On Sun, Jul 20, 2008 at 11:14:10PM -0700, Nick Lewycky wrote: > This testcase produces different output depending on whether -O1 or -O2 is > specified. The testcase is wrong. Please produce a _minimal_ variant, it even shows the same behaviour without bitfields. Please explain what exactly the fo

Bug#491653: gcc-4.3: misoptimization of 64-bit bitfield when not byte aligned

2008-07-20 Thread Nick Lewycky
Package: gcc-4.3 Version: 4.3.1-6 Severity: normal This testcase produces different output depending on whether -O1 or -O2 is specified. Correct: # gcc PR1386.c -o pr1386 -O1 PR1386.c: In function ‘main’: PR1386.c:15: warning: large integer implicitly truncated to unsigned typ