/*
Bug in mpir 1.2.1.
This program demonstrates that mpn_lshift, as implemented on 64 bit
intel
machines by mpn/x86_64/core2/lshift.as, gives the wrong answer if
the limbs
are not aligned to an 8 byte boundary.
The confusion in the code starts with these lines:
and r9, -16
movdqa xmm3, [r9]
In mpir 1.3.0-rc3, that file is gone, but the same faulty code
lingers on in
the following files, which may need attention:
mpn/x86_64/k8/k10/lshift.as
mpn/x86_64/atom/lshift.as
Even if the default allocator always returns 8-byte aligned memory
blocks,
this is still a bug, because the documentation on "Custom
Allocation"
doesn't require custom memory allocators to obey any alignment
requirements.
Here's the output from the program
5285209847924392297689518137364380393182068736
5285209916707841180605126409194605050347913216
Correct output would have the second line the same as the first.
Linux fedora64 2.6.31.6-162.fc12.x86_64 #1 SMP Fri Dec 4 00:06:26
EST 2009 x86_64 x86_64 x86_64 GNU/Linux
gcc version 4.4.2 20091027 (Red Hat 4.4.2-7) (GCC)
*/
#include <stdio.h>
#include <stdlib.h>
#include <gmp.h>
#include <assert.h>
int main (int argc, char **argv) {
mpz_t rp, sp;
mpz_init2 (rp, 10 * 64);
mpz_init2 (sp, 10 * 64);
mpz_set_str (rp, "660651230990549037211189767170547549147758592",
10);
mpz_set_str (sp, "660651230990549037211189767170547549147758592",
10);
mpn_lshift (rp -> _mp_d, sp -> _mp_d, 3, 3);
mpz_out_str(stdout, 10, rp);
printf("\n");
sp->_mp_d = (mp_limb_t *)((char *)sp->_mp_d + 4);
mpz_set_str (sp, "660651230990549037211189767170547549147758592",
10);
mpn_lshift (rp -> _mp_d, sp -> _mp_d, 3, 3);
mpz_out_str(stdout, 10, rp);
printf("\n");
return 0;
}
--
You received this message because you are subscribed to the Google Groups
"mpir-devel" group.
To post to this group, send email to mpir-de...@googlegroups.com.
To unsubscribe from this group, send email to
mpir-devel+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/mpir-devel?hl=en.
