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__m64 and aliasing
- From: Jan Hubicka <jh at suse dot cz>
- To: gcc-bugs at gcc dot gnu dot org, rth at cygnus dot com, bernds at redhat dot com
- Date: Wed, 19 Jun 2002 15:46:33 +0200
- Subject: __m64 and aliasing
Hi,
bugreport 6783 seems to show alliasing problem in:
unsigned char a[8] = { 1, 2, 3, 4, 5, 6, 7, 8 };
unsigned char b[8] = { 10, 20, 30, 40, 50, 60, 70, 80 };
unsigned char c[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
__m64 m0, m1, m2;
int i;
m0 = *(__m64 *) a;
m1 = *(__m64 *) b;
m2 = _mm_adds_pu8 (m0, m1);
GCC appears to assume that the copy from a to m0 does not alias with the
array so the initialization code is scheduled afterwards.
Is the testcase buggy or we need to fix the aliasing problem?
Honza