I'm using the stock Fedora 12 gcc, RPM gcc-4.4.3-4.fc12.x86_64.
Whereas it appears to align __m128 variables correctly (16-bytes), it accesses
them as if they were only 8 byte aligned.
I read various threads etc about aligning variables on the stack, but my belief
is that this never was a problem on x86_64, and in fact using gcc-4.3.2 it
generates the expected code.
#include <xmmintrin.h>
void
test(__m128 *x)
{
volatile __m128 tmp = *x;
}
generates
gcc-4.4.3-4.fc12
0000000000000000 <test>:
0: 55 push %rbp
1: 48 89 e5 mov %rsp,%rbp
4: 48 89 7d e8 mov %rdi,-0x18(%rbp)
8: 48 8b 45 e8 mov -0x18(%rbp),%rax
c: 0f 28 00 movaps (%rax),%xmm0
f: 0f 13 45 f0 movlps %xmm0,-0x10(%rbp)
13: 0f 17 45 f8 movhps %xmm0,-0x8(%rbp)
17: c9 leaveq
18: c3 retq
gcc-4.3.2: (correct)
0000000000000000 <test>:
0: 55 push %rbp
1: 48 89 e5 mov %rsp,%rbp
4: 48 89 7d e8 mov %rdi,0xffffffffffffffe8(%rbp)
8: 48 8b 45 e8 mov 0xffffffffffffffe8(%rbp),%rax
c: 0f 28 00 movaps (%rax),%xmm0
f: 0f 29 45 f0 movaps %xmm0,0xfffffffffffffff0(%rbp)
13: c9 leaveq
14: c3 retq
--
Summary: SSE2 / stack align
Product: gcc
Version: 4.4.3
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: kai dot germaschewski at gmail dot com
GCC build triplet: x86_64-redhat-linux
GCC host triplet: x86_64-redhat-linux
GCC target triplet: x86_64-redhat-linux
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43124
