Red Hat Bugzilla – Bug 37054
GCC optimizer bug; miscompiles kernel sym53c8xx driver
Last modified: 2007-04-18 12:32:47 EDT
gcc-2.96-81 -O2 miscompiles the attached code. RedHat 7.1 sym53c8xx SCSI
driver is affected, on my system (Tekram 53C860) RH7.1 install program
causes "oops" (non-fatal, but you can't access SCSI) when insmoding
Steps to Reproduce:
1. install Tekram 310U (or possibly other NCR53C8xx-based) SCSI PCI card
2. run RH7.1 install from CD
3. watch the screen
Actual Results: $ gcc -O2 test.c -o test
x = 0 (should be 8)
unsigned int x = 8;
if (x < 5)
x = 4;
x = 8;
printf("x = %u (should be 8)\n", x);
I haven't tested current gcc compilers, possibly the problem should be
corrected there as well.
Verified, looks like a bug in ia32's ix86_expand_int_movcc,
happens in gcc 3.0 and gcc 3.1 as well.
Hope to have this debugged by tomorrow.
Fixed by http://gcc.gnu.org/ml/gcc-patches/2001-04/msg01057.html
and will be included in the upcoming gcc-2.96-82.
*** Bug 39764 has been marked as a duplicate of this bug. ***