Actual version string from gcc: 4.1.2 20060928 (prerelease) (Ubuntu 4.1.1-13ubuntu5)
Configured with: ../src/configure -v --enable-languages=c,c++,fortran,objc,obj-c++,treelang --prefix=/usr --enable-shared --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --enable-nls --program-suffix=-4.1 --enable-__cxa_atexit --enable-clocale=gnu --enable-libstdcxx-debug --enable-mpfr --enable-checking=release x86_64-linux-gnu Using __builtin_prefetch with the default compiler flags (i.e, mtune=generic) generates a 3dnow prefetch instruction (prefetchw), which won't run on em64t cpus. Attaching test file. Compiling this with gcc -otest test.c produces a binary that faults on em64t. Compiling with 'gcc -o test -mno-3dnow test.c' generates a prefetcht0 instruction, which works. -- Summary: gcc 4.1.2 on x86_64 Ubuntu Edgy generates incorrect prefetch instruction Product: gcc Version: 4.1.2 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: thaytan at noraisin dot net GCC host triplet: x86_64-linux-gnu GCC target triplet: x86_64-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29833