.file "wm_shrx.S"
/*---------------------------------------------------------------------------+
| wm_shrx.S |
| |
| 64 bit right shift functions |
| |
| Copyright (C) 1992,1995 |
| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, |
| Australia. E-mail billm@jacobi.maths.monash.edu.au |
| |
| Call from C as: |
| unsigned FPU_shrx(void *arg1, unsigned arg2) |
| and |
| unsigned FPU_shrxs(void *arg1, unsigned arg2) |
| |
+---------------------------------------------------------------------------*/
#include "fpu_emu.h"
.text
/*---------------------------------------------------------------------------+
| unsigned FPU_shrx(void *arg1, unsigned arg2) |
| |
| Extended shift right function. |
| Fastest for small shifts. |
| Shifts the 64 bit quantity pointed to by the first arg (arg1) |
| right by the number of bits specified by the second arg (arg2). |
| Forms a 96 bit quantity from the 64 bit arg and eax: |
| [ 64 bit arg ][ eax ] |
| shift right ---------> |
| The eax register is initialized to 0 before the shifting. |
| Results returned in the 64 bit arg and eax. |
+---------------------------------------------------------------------------*/
ENTRY(FPU_shrx)
push %ebp
movl %esp,%ebp
pushl %esi
movl PARAM2,%ecx
movl PARAM1,%esi
cmpl $32,%ecx /* shrd only works for 0..31 bits */
jnc L_more_than_31
/* less than 32 bits */
pushl %ebx
movl (%esi),%ebx /* lsl */
movl 4(%esi),%edx /* msl */
xorl %eax,%eax /* extension */
shrd %cl,%ebx,%eax
shrd %cl,%edx,%ebx
shr %cl,%edx
movl %ebx,(%esi)
movl %edx,4(%esi)
popl %ebx
popl %esi
leave
ret
L_more_than_31:
cmpl $64,%ecx
jnc L_more_than_63
subb $32,%cl
movl (%esi),%eax /* lsl */
movl 4(%esi),%edx /* msl */
shrd %cl,%edx,%eax
shr %cl,%edx
movl %edx,(%esi)
movl $0,4(%esi)
popl %esi
leave
ret
L_more_than_63:
cmpl $96,%ecx
jnc L_more_than_95
subb $64,%cl
movl 4(%esi),%eax /* msl */
shr %cl,%eax
xorl %edx,%edx
movl %edx,(%esi)
movl %edx,4(%esi)
popl %esi
leave
ret
L_more_than_95:
xorl %eax,%eax
movl %eax,(%esi)
movl %eax,4(%esi)
popl %esi
leave
ret
/*---------------------------------------------------------------------------+
| unsigned FPU_shrxs(void *arg1, unsigned arg2) |
| |
| Extended shift right function (optimized for small floating point |
| integers). |
| Shifts the 64 bit quantity pointed to by the first arg (arg1) |
| right by the number of bits specified by the second arg (arg2). |
| Forms a 96 bit quantity from the 64 bit arg and eax: |
| [ 64 bit arg ][ eax ] |
| shift right ---------> |
| The eax register is initialized to 0 before the shifting. |
| The lower 8 bits of eax are lost and replaced by a flag which is |
| set (to 0x01) if any bit, apart from the first one, is set in the |
| part which has been shifted out of the arg. |
| Results returned in the 64 bit arg and eax. |
+---------------------------------------------------------------------------*/
ENTRY(FPU_shrxs)
push %ebp
movl %esp,%ebp
pushl %esi
pushl %ebx
movl PARAM2,%ecx
movl PARAM1,%esi
cmpl $64,%ecx /* shrd only works for 0..31 bits */
jnc Ls_more_than_63
cmpl $32,%ecx /* shrd only works for 0..31 bits */
jc Ls_less_than_32
/* We got here without jumps by assuming that the most common requirement
is for small integers */
/* Shift by [32..63] bits */
subb $32,%cl
movl (%esi),%eax /* lsl */
movl 4(%esi),%edx /* msl */
xorl %ebx,%ebx
shrd %cl,%eax,%ebx
shrd %cl,%edx,%eax
shr %cl,%edx
orl %ebx,%ebx /* test these 32 bits */
setne %bl
test $0x7fffffff,%eax /* and 31 bits here */
setne %bh
orw %bx,%bx /* Any of the 63 bit set ? */
setne %al
movl %edx,(%esi)
movl $0,4(%esi)
popl %ebx
popl %esi
leave
ret
/* Shift by [0..31] bits */
Ls_less_than_32:
movl (%esi),%ebx /* lsl */
movl 4(%esi),%edx /* msl */
xorl %eax,%eax /* extension */
shrd %cl,%ebx,%eax
shrd %cl,%edx,%ebx
shr %cl,%edx
test $0x7fffffff,%eax /* only need to look at eax here */
setne %al
movl %ebx,(%esi)
movl %edx,4(%esi)
popl %ebx
popl %esi
leave
ret
/* Shift by [64..95] bits */
Ls_more_than_63:
cmpl $96,%ecx
jnc Ls_more_than_95
subb $64,%cl
movl (%esi),%ebx /* lsl */
movl 4(%esi),%eax /* msl */
xorl %edx,%edx /* extension */
shrd %cl,%ebx,%edx
shrd %cl,%eax,%ebx
shr %cl,%eax
orl %ebx,%edx
setne %bl
test $0x7fffffff,%eax /* only need to look at eax here */
setne %bh
orw %bx,%bx
setne %al
xorl %edx,%edx
movl %edx,(%esi) /* set to zero */
movl %edx,4(%esi) /* set to zero */
popl %ebx
popl %esi
leave
ret
Ls_more_than_95:
/* Shift by [96..inf) bits */
xorl %eax,%eax
movl (%esi),%ebx
orl 4(%esi),%ebx
setne %al
xorl %ebx,%ebx
movl %ebx,(%esi)
movl %ebx,4(%esi)
popl %ebx
popl %esi
leave
ret
