| Summary: | floor() is giving incorrect results on alpha | ||
|---|---|---|---|
| Product: | glibc | Reporter: | Aurelien Jarno <aurelien> |
| Component: | math | Assignee: | rth <rth> |
| Status: | RESOLVED FIXED | ||
| Severity: | normal | CC: | glibc-bugs |
| Priority: | P2 | Flags: | fweimer:
security-
|
| Version: | unspecified | ||
| Target Milestone: | --- | ||
| Host: | alphaev68-unknown-linux-gnu | Target: | alphaev68-unknown-linux-gnu |
| Build: | alphaev68-unknown-linux-gnu | Last reconfirmed: | |
| Attachments: | Patch to revert the code to the old version | ||
Created attachment 2094 [details]
Patch to revert the code to the old version
Patch applied: 116ff9ad1801108d084fd9ff94241f26a33dff1c |
floor() is giving wrong result for some corner cases on alpha, as shown by the following testcase: #include <assert.h> #include <float.h> #include <math.h> #include <stdio.h> int main() { double x; printf("%s%d\n", "DBL_MANT_DIG = ", DBL_MANT_DIG); x = ldexp (1.0, DBL_MANT_DIG) - 1.0; printf("%lf %lf\n", x, floor(x)); assert(x == floor(x)); /* does not work in alpha */ return 0; } It is actually a regression introduced by the following changesets: 2007-03-14 Richard Henderson <rth@redhat.com> * sysdeps/alpha/fpu/s_ceil.c: Rewrite without branches. * sysdeps/alpha/fpu/s_ceilf.c: Likewise. * sysdeps/alpha/fpu/s_floor.c: Likewise. * sysdeps/alpha/fpu/s_floorf.c: Likewise. * sysdeps/alpha/fpu/s_rint.c: Likewise. * sysdeps/alpha/fpu/s_rintf.c: Likewise. This change also assumes that the internal FPU representation has the same precision as the IEEE one, which is not always true.