http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47062
Summary: -mfpmath=sse,387 causes pow() to produce incorrect
results
Product: gcc
Version: 4.5.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: other
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: b...@arklinux.org
Host: x86_64-pc-linux-gnu
Target: x86_64-pc-linux-gnu
Build: x86_64-pc-linux-gnu
If (e)glibc is compiled with -mfpmath=sse,387, the pow() (and __builtin_pow())
function provides incorrect [beyond expectable inaccuracies] results.
#include <math.h>
#include <stdio.h>
int main(int argc, char **argv) {
double n = 0.703167;
printf("%f %f %f\n", pow(n, 1.0/2.2), __builtin_pow(n, 1.0/2.2),
pow(0.703167, 1.0/2.2));
}
(correctly) results in
0.852081 0.852081 0.852081
without -mfpmath=sse,387.
With -mfpmath=sse,387, the result is
1.000014 1.000014 0.852081
