From Bugzilla Helper: User-Agent: Mozilla/4.77 [en] (X11; U; Linux 2.2.19-7.0.1 i686) Description of problem: We believe we have found a bug in gcc. We have been trying to track down why .../drivers/scsi/sym53c8xx.c driver oopses when initializing at line 5265, which reads: period = (4 * div_10M[0] + np->clock_khz - 1) / np->clock_khz; We believe the bug is that gcc is generating incorrect code for this: if (f1 < 55000) f1 = 40000; else f1 = 80000; Here is the test code to demonstrate this: % cat bug.c int main (int argc, char *argv[]) { unsigned f1; f1 = (unsigned)argc; if (f1 < 5) { f1 = 4; } else { f1 = 8; } exit (f1); } And here are commands to exhibit the problem. % for i in 0 1 2 3 4 5 6 ; do ln bug.c bug$i.c ; done % for i in 0 1 2 3 4 5 6 ; do gcc -save-temps -O$i -o bug$i bug$i.c ; done % for i in 0 1 2 3 4 5 6 ; do ./bug$i 1 2 ; echo $? ; done % for i in 0 1 2 3 4 5 6 ; do ./bug$i 1 2 3 4 5 6 7 ; echo $? ; done The level 0 optimization assembly code appears correct. For level 1 and above, the compiler emits a long subtract with borrow statement which leaves EAX either 0 filled or 1 filled, based on the carry flag. As this is with Red Hat's gcc, I'm not sending this to the gcc. Versions with this problem include gcc-2.96-69 and gcc-2.96-81. How reproducible: Always Steps to Reproduce: follow example above Additional info:
*** This bug has been marked as a duplicate of 37054 ***