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|
/*---------------------------------------------------------------------------+
| reg_norm.S |
| |
| Copyright (C) 1992,1993,1994,1995 |
| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, |
| Australia. E-mail billm@jacobi.maths.monash.edu.au |
| |
| Normalize the value in a FPU_REG. |
| |
| Call from C as: |
| void normalize(FPU_REG *n) |
| |
| void normalize_nuo(FPU_REG *n) |
| |
+---------------------------------------------------------------------------*/
#include "fpu_emu.h"
.text
ENTRY(normalize)
pushl %ebp
movl %esp,%ebp
pushl %ebx
movl PARAM1,%ebx
#ifdef PARANOID
cmpb TW_Valid,TAG(%ebx)
je L_ok
pushl $0x220
call SYMBOL_NAME(FPU_exception)
addl $4,%esp
L_ok:
#endif PARANOID
movl SIGH(%ebx),%edx
movl SIGL(%ebx),%eax
orl %edx,%edx /* ms bits */
js L_done /* Already normalized */
jnz L_shift_1 /* Shift left 1 - 31 bits */
orl %eax,%eax
jz L_zero /* The contents are zero */
movl %eax,%edx
xorl %eax,%eax
subl $32,EXP(%ebx) /* This can cause an underflow */
/* We need to shift left by 1 - 31 bits */
L_shift_1:
bsrl %edx,%ecx /* get the required shift in %ecx */
subl $31,%ecx
negl %ecx
shld %cl,%eax,%edx
shl %cl,%eax
subl %ecx,EXP(%ebx) /* This can cause an underflow */
movl %edx,SIGH(%ebx)
movl %eax,SIGL(%ebx)
L_done:
cmpl EXP_OVER,EXP(%ebx)
jge L_overflow
cmpl EXP_UNDER,EXP(%ebx)
jle L_underflow
L_exit:
popl %ebx
leave
ret
L_zero:
movl EXP_UNDER,EXP(%ebx)
movb TW_Zero,TAG(%ebx)
jmp L_exit
L_underflow:
push %ebx
call SYMBOL_NAME(arith_underflow)
pop %ebx
jmp L_exit
L_overflow:
push %ebx
call SYMBOL_NAME(arith_overflow)
pop %ebx
jmp L_exit
/* Normalise without reporting underflow or overflow */
ENTRY(normalize_nuo)
pushl %ebp
movl %esp,%ebp
pushl %ebx
movl PARAM1,%ebx
#ifdef PARANOID
cmpb TW_Valid,TAG(%ebx)
je L_ok_nuo
pushl $0x221
call SYMBOL_NAME(FPU_exception)
addl $4,%esp
L_ok_nuo:
#endif PARANOID
movl SIGH(%ebx),%edx
movl SIGL(%ebx),%eax
orl %edx,%edx /* ms bits */
js L_exit /* Already normalized */
jnz L_nuo_shift_1 /* Shift left 1 - 31 bits */
orl %eax,%eax
jz L_zero /* The contents are zero */
movl %eax,%edx
xorl %eax,%eax
subl $32,EXP(%ebx) /* This can cause an underflow */
/* We need to shift left by 1 - 31 bits */
L_nuo_shift_1:
bsrl %edx,%ecx /* get the required shift in %ecx */
subl $31,%ecx
negl %ecx
shld %cl,%eax,%edx
shl %cl,%eax
subl %ecx,EXP(%ebx) /* This can cause an underflow */
movl %edx,SIGH(%ebx)
movl %eax,SIGL(%ebx)
jmp L_exit
|
