Call expander ignores type alignment. But caller honors type alignment.
It usually isn't a problem until the argument is passed via stack. We
have a mismatch between caller and callee:
bash-3.2$ cat x.c
typedef float __m128 __attribute__ ((__vector_size__ (16), __may_alias__));
__m128 __attribute__((noinline))
iszero (__m128 x)
{
return x;
}
typedef __m128 __attribute__((aligned(1))) unaligned;
__m128 __attribute__((noinline))
foo (__m128 a1, __m128 a2, __m128 a3, __m128 a4,
__m128 a5, __m128 a6, __m128 a7, __m128 a8,
int b1, int b2, int b3, int b4, int b5, int b6, int b7, unaligned y)
{
return iszero (y);
}
int
main (void)
{
unaligned x;
__m128 y, x0 = { 0 };
x = x0;
y = foo (x0, x0, x0, x0, x0, x0, x0, x0, 1, 2, 3, 4, 5, 6, 7, x);
return __builtin_memcmp (&y, &x0, sizeof (y));
}
bash-3.2$ make
/export/build/gnu/gcc/build-x86_64-linux/stage1-gcc/xgcc
-B/export/build/gnu/gcc/build-x86_64-linux/stage1-gcc/ -O -g -c -o x.o x.c
/export/build/gnu/gcc/build-x86_64-linux/stage1-gcc/xgcc
-B/export/build/gnu/gcc/build-x86_64-linux/stage1-gcc/ x.o -o x
./x
make: *** [all] Segmentation fault
bash-3.2$ gdb x
GNU gdb Red Hat Linux (6.6-45.fc8rh)
Copyright (C) 2006 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
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This GDB was configured as "x86_64-redhat-linux-gnu"...
Using host libthread_db library "/lib64/libthread_db.so.1".
(gdb) r
Starting program: /export/home/hjl/bugs/gcc/35767/x
Program received signal SIGSEGV, Segmentation fault.
foo (a1={0, 0, 0, 0}, a2={0, 0, 0, 0}, a3={0, 0, 0, 0}, a4={0, 0, 0, 0}, a5=
{0, 0, 0, 0}, a6={0, 0, 0, 0}, a7={0, 0, 0, 0}, a8={0, 0, 0, 0}, b1=1,
b2=2, b3=3, b4=4, b5=5, b6=6, b7=7, y={5.87934249e-39, 0, 0, 0}) at x.c:16
^^^^^^^^^^^^^^^^^^^^^^^^^
Should be {0, 0, 0, 0}
16 return iszero (y);
Missing separate debuginfos, use: debuginfo-install glibc.x86_64
(gdb) f 1
#1 0x00000000004004c3 in main () at x.c:25
25 y = foo (x0, x0, x0, x0, x0, x0, x0, x0, 1, 2, 3, 4, 5, 6, 7, x);
(gdb) p x
No symbol "x" in current context.
(gdb) p x0
$1 = {0, 0, 0, 0}
(gdb)
The segfault is PR 35767.
--
Summary: Call expander ignores type alignment
Product: gcc
Version: 4.4.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: hjl dot tools at gmail dot com
GCC target triplet: x86_64-unknown-linux-gnu
BugsThisDependsOn: 35767
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35771
