------- Comment #7 from leonid at volnitsky dot com 2008-12-14 22:32 -------
(In reply to comment #2)
> ... please reduce your source to a
> short, self contained runtime testcase (in plain C if possible) that fails
> with
> certain compile flags.
I've tried to do that (see below). But unfortunately it does not exhibit same
behavior. It will fail on any optimized compile with warning about aliasing.
Which is fixable by adding -fno-strict-aliasing. Don't know if this is related
on not.
---------------------------------------------------------
#include <immintrin.h>
#include <stdio.h>
int main(int argc, char *argv[]) {
int16_t volatile A[2000];
for (int i=0; i<(2000-2); i+=2) { A[i]=1; A[i+1]=2; }; A[333] = 3;
#define mk_m128i(x) *(__m128i*)&(x)
__m128i m1 = mk_m128i(A[0]);
__m128i m2 = mk_m128i(A[8]);
for (int i= 16; i < 2000-16; i+=16) { // SSE
m1 = _mm_max_epi16(m1, mk_m128i(A[i]) );
m2 = _mm_max_epi16(m2, mk_m128i(A[i+8]) );
}
m1 = _mm_max_epi16(m1, m2);
int16_t* ip = (int16_t*)&m1;
printf("%hi %hi %hi %hi %hi %hi %hi %hi \n", *ip++, *ip++, *ip++,
*ip++, *ip++, *ip++, *ip++, *ip);
return 0;
}
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38525
