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Re: x86 regression: optimizer bug in 1.1 and dev
- To: Mumit Khan <khan at xraylith dot wisc dot edu>
- Subject: Re: x86 regression: optimizer bug in 1.1 and dev
- From: Horst von Brand <vonbrand at sleipnir dot valparaiso dot cl>
- Date: Mon, 09 Nov 1998 20:31:56 -0400
- cc: egcs-bugs at cygnus dot com
Mumit Khan <khan@xraylith.wisc.edu> said:
> Versions affected: 1.1 and development snapshots. REGRESSION from 1.0.3.
>
> The following optimizer bug shows up on i686-pc-linux-gnu, i386-*win32
> (and possibly other x86) ports when using -Ox, x >= 2.
>
> Thanks to Peter Kabal <Kabal@ece.mcgill.ca> for the report and attached
> testcase.
>
> To reproduce on i686-pc-linux-gnu:
>
> $ gcc -O2 -D__NO_MATH_INLINES -o floor-bug floor-bug.c
> $ ./floor-bug
> AV = 20, AV - floor(AV) = -1.11022e-15
> ^^^^^^^^^^^^ should always be >= 0
>
> Note that -D__NO_MATH_INLINES is necessary to reproduce the bug on glibc2.
This is i586, egcs-1.1, linux-2.1.127arca12, binutils-2.9.1.0.15,
glibc-2.0.100
I see the exact same result here, but I had to add -lm to link in the math
library. You sure it's not a glibc bug (no -D__NO_MATH_INLINES gives:
AV = 20, AV - floor(AV) = 1
and libm is _not_ used).
--
Horst von Brand vonbrand@sleipnir.valparaiso.cl
Casilla 9G, Viņa del Mar, Chile +56 32 672616