[Linux-ia64] unalinged access by loadpair instruction

Hideki Yamamoto
2002-12-09T14:28:45Z

Hi everyone,

When unaligned access is happened by loadpair
instruction, reloading by kernel is wrong.

When unalined access is happeded by loadpair
instruction in NORMAL loop, it is no problem.
Please try to run the attached programs(c.c and a.s)
compiled by gcc.

However, When it is happned by loadpair instruction in
SWP loop, it fails to reload the data.
Please try to run the attached programs(c.c and aa.s)
compiled by gcc. aa.s is included loadpair in SWP loop.
If there is no happening, please change the n
parameter to bigger number.

Sorry, I could not isolate whether or not it is caused
by HW bug or Kernel problem.

Let me know somebody understood the cause why it is happened.

Thanks.

-- c.c
#define n 100
double d[n],d2[n+1];
main() {
int i,j;

for( i = 0; i < n; i++ ) {
d[i] = 123.0;
d2[i] = 0.0;
}
// verify
for( i = 0; i < n; i++ ) {
if( d[i] != 123.0 ) {
printf("Assignment to d[%d] is wrong\n", i);
exit(-1);
}
}
printf("Verify is ok\n");
copy_by_loadpair(&d, &d2, n);
for( i = 0; i < n; i++ ) {
if( d2[i] != 123.0 ) {
printf("Something is wrong!!\n d2[%d] = %f(should be d[%d]=%f)\n", i, d2[i], i, d[i]);
printf("%f\n", d2[i+1]);
}
}
}

-- a.s
.file "a.c"
.pred.safe_across_calls p1-p5,p16-p63
.text
.align 16
.global copy_by_loadpair#
.proc copy_by_loadpair#
copy_by_loadpair:
{ .mmi
alloc r8=ar.pfs,3,0,0,0 ;; //0: 1 19
nop.m 0
add r17=1,r0
}
L1:
{ .mii
ldfpd f6,f7=[r32] //1: 2 4
add r2=8,r33 //1: 3 8
nop.i 0
}
{ .mmi
nop.m 0 ;; //1: 3 6
stfd [r33]ö
add r33=8,r33
}
{ .mmi
nop.m 0 ;; //10: 3 7
stfd [r2]÷ //19: 3 9
add r32=8,r32;;
}
{ .mib
cmp4.ne p8,p0=r17,r34
add r17=1,r17
(p8) br.cond.dpnt.many L1 ;; //7: 3 19
}
{ .mib
nop.m 0
nop.i 0
br.ret.sptk.many b0 ;; //19: 4 10
}
.endp get_by_loadpair#
--
.file "a.c"
.pred.safe_across_calls p1-p5,p16-p63
.text
.align 16
.global copy_by_loadpair#
.proc copy_by_loadpair#
copy_by_loadpair:
{ .mmi
alloc r8=ar.pfs,3,6,0,0 ;;
nop.m 0
add r17=1,r0
}
{ .mmi
add r15=0,r32
add r2=0,r33
add r3=8,r33;;
}
{ .mii
nop.m 0
mov ar.lc=r34
nop.i 0 ;;
}
{ .mii
nop.m 0
mov pr.rot=0x10000 ;;
mov ar.ec=5 ;;
}
L1:
{ .mmi
(p16) ldfpd f32,f33=[r15]
(p16) add r15=8,r15
nop.i 0
}
{ .mmb
(p20) stfd [r3]ó7,8
//nop.m 0
(p20) stfd [r2]ó6,8
br.ctop.sptk L1
}
{ .mib
nop.m 0
nop.i 0
br.ret.sptk.many b0 ;; //19: 4 10
}
.endp get_by_loadpair#