------- Comment #6 from tim at klingt dot org 2008-12-31 09:20 ------- > sys_perf_counter_open always returns less than zero for me. > This is with: > Linux gcc13 2.6.18-6-vserver-amd64 #1 SMP Sun Feb 10 17:55:04 UTC 2008 x86_64 > GNU/Linux > > What system call is it trying to do and why? >
it is trying to open the performance counters (http://lwn.net/Articles/310176/). it requires a patched kernel, though ... (In reply to comment #3) > t.cc: In function �float __vector__ nova::detail::gen_one()�: > t.cc:34160: warning: �x� is used uninitialized in this function > > inline __m128 gen_one(void) > { > __m128i x; > __m128i ones = _mm_cmpeq_epi32(x, x); > return (__m128)_mm_slli_epi32 (_mm_srli_epi32(ones, 25), 23); > } > > Is undefined code I think. this code is valid. the uninitialized xmm register x is compared with itself in order to set the register ones to ffffffffffffffffffffffffffffffff. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38671
