Date: Tue, 3 Apr 2012 14:21:11 +0300 From: Andrey Simonenko <simon@comsys.ntu-kpi.kiev.ua> To: freebsd-current@freebsd.org Subject: -ffast-math in Ports and wrong generated code Message-ID: <20120403112111.GA39616@pm513-1.comsys.ntu-kpi.kiev.ua>
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Hello,
I use one port from the Ports Collection, that works with FP. Having
reinstalled it (its version was not changed) I noticed that it started
to work incorrectly. After debugging and disassembling its code I found
out that the -ffast-math option used for building was the result of
wrongly generated code (I did not specify this option in /etc/make.conf).
At least finite() function call was eliminated from the result Assembler
code when -ffast-math option is used, tested on 9.0-STABLE and 10.0-CURRENT.
Example test source code and generated code under 9.0-STABLE on amd64
by gcc from the base system:
-----------------------------
#include <math.h>
#include <stdio.h>
void
check_finite(double x)
{
printf("%d\n", finite(x));
}
-----------------------------
% gcc -Wall -O2 -S finite.c
-----------------------------
check_finite:
.LFB3:
subq $8, %rsp
.LCFI0:
call finite <-- call to finite()
movl $.LC0, %edi
movl %eax, %esi
addq $8, %rsp
xorl %eax, %eax
jmp printf
.LFE3:
.size check_finite, .-check_finite
-----------------------------
% gcc -Wall -O2 -ffast-math -S finite.c
-----------------------------
check_finite:
.LFB3:
xorl %esi, %esi <-- fake result from finite()
movl $.LC0, %edi
xorl %eax, %eax
jmp printf
.LFE3:
.size check_finite, .-check_finite
-----------------------------
Can somebody comment this?
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