http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50190
Bug #: 50190 Summary: linkpk bench of polyhedron fails during validation with gcc trunk when it is compiled with -Ofast on amd64. Classification: Unclassified Product: gcc Version: 4.7.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: rtl-optimization AssignedTo: unassig...@gcc.gnu.org ReportedBy: venkataramanan.kumar....@gmail.com Polyhedron benchmark linpk fails during validation when compiled with -Ofast flag. (Snip) > Value= 25.114499300 Target= 23.100000000 Tolerance= 2.0000000000 FAIL <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< > Value=0.27880142600E-10 Target=0.27858826400E-10 Tolerance=0.10000000000E-09 > Value=0.22204460500E-15 Target=0.22204460500E-15 Tolerance=0.10000000000E-14 > Value= 1.0000000000 Target= 1.0000000000 Tolerance=0.10000000000E-07 > Value= 1.0000000000 Target= 1.0000000000 Tolerance=0.10000000000E-07 linpk FAILED 1 fails and 4 passes (Snip) exact version of GCC: gcctrunk 1780539 system type: amd64 options given when GCC was configured/built: --disable-bootstrap --without-ppl --without-cloog --enable-languages=c,c++,fortran complete command line that triggers the bug: -Ofast This issue does not occur when -fprotect-parens is specified with -Ofast. Current trunk has -fno-protect-parens in -Ofast. So this seems to be a precision issue as GCC may reorder floating point computations. But I have reported this to bring it to the notice of community.