Current mainline gcc appears to miscompile the following code:
======begin======
static void foo (double a, double weight, const double *ring, double *phase)
{
*phase = *ring * weight;
}
static void foo2 (void)
{ foo (0, 1, (double*)0, (double*)0); }
static void foo3 (void)
{ foo2(); }
void foo4 (void)
{ foo3(); }
int main(void)
{
double t1=1, c1;
foo(0,1,&t1,&c1);
return (c1>0.5) ? 1:0;
}
=======end=======
/scratch/martin/libpsht-0.2>gcc -v -O -ffast-math psht_test.c -lm
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: /scratch/martin/gcc/configure
--prefix=/afs/mpa/data/martin/ugcc --enable-languages=c
--enable-checking=release
Thread model: posix
gcc version 4.3.0 20061115 (experimental)
/afs/mpa/data/martin/ugcc/libexec/gcc/i686-pc-linux-gnu/4.3.0/cc1 -quiet -v
psht_test.c -quiet -dumpbase psht_test.c -mtune=generic -auxbase psht_test -O
-version -ffast-math -o /tmp/ccSNsfEN.s
ignoring nonexistent directory
"/afs/mpa/data/martin/ugcc/lib/gcc/i686-pc-linux-gnu/4.3.0/../../../../i686-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/local/include
/afs/mpa/data/martin/ugcc/include
/afs/mpa/data/martin/ugcc/lib/gcc/i686-pc-linux-gnu/4.3.0/include
/usr/include
End of search list.
GNU C version 4.3.0 20061115 (experimental) (i686-pc-linux-gnu)
compiled by GNU C version 4.3.0 20061115 (experimental).
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: e4c043f86c42a15259a6956a912800d1
as -V -Qy -o /tmp/cc424C9p.o /tmp/ccSNsfEN.s
GNU assembler version 2.16.1 (i686-pc-linux-gnu) using BFD version 2.16.1
/afs/mpa/data/martin/ugcc/libexec/gcc/i686-pc-linux-gnu/4.3.0/collect2
--eh-frame-hdr -m elf_i386 -dynamic-linker /lib/ld-linux.so.2 /usr/lib/crt1.o
/usr/lib/crti.o
/afs/mpa/data/martin/ugcc/lib/gcc/i686-pc-linux-gnu/4.3.0/crtbegin.o
-L/afs/mpa/data/martin/ugcc/lib/gcc/i686-pc-linux-gnu/4.3.0
-L/afs/mpa/data/martin/ugcc/lib/gcc/i686-pc-linux-gnu/4.3.0/../../..
/tmp/cc424C9p.o -lm -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc
--as-needed -lgcc_s --no-as-needed
/afs/mpa/data/martin/ugcc/lib/gcc/i686-pc-linux-gnu/4.3.0/crtfastmath.o
/afs/mpa/data/martin/ugcc/lib/gcc/i686-pc-linux-gnu/4.3.0/crtend.o
/usr/lib/crtn.o
/scratch/martin/libpsht-0.2>./a.out
/scratch/martin/libpsht-0.2>echo $?
0
The correct exit code would be 1.
I did some regression hunting, and the problem appears to have been
introduced to SVN with revision 118859 (introduction of -mx87regparm by Uros
Bizjak).
The compiled code behaves correctly if
- the "-ffast-math" flag is omitted, and/or
- the functions foo2() - foo4() (which are not called anyway) are removed
--
Summary: silent miscompilation of argument passing(?)
Product: gcc
Version: 4.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: martin at mpa-garching dot mpg dot de
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30120
