/*---------------------------------------------------------------------------+
| reg_norm.S |
| |
| Copyright (C) 1992,1993,1994,1995,1997 |
| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, |
| Australia. E-mail billm@suburbia.net |
| |
| Normalize the value in a FPU_REG. |
| |
| Call from C as: |
| int FPU_normalize(FPU_REG *n) |
| |
| int FPU_normalize_nuo(FPU_REG *n) |
| |
| Return value is the tag of the answer, or-ed with FPU_Exception if |
| one was raised, or -1 on internal error. |
| |
+---------------------------------------------------------------------------*/
#include "fpu_emu.h"
.text
ENTRY(FPU_normalize)
pushl %ebp
movl %esp,%ebp
pushl %ebx
movl PARAM1,%ebx
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
subw $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
subw %cx,EXP(%ebx) /* This can cause an underflow */
movl %edx,SIGH(%ebx)
movl %eax,SIGL(%ebx)
L_done:
cmpw EXP_OVER,EXP(%ebx)
jge L_overflow
cmpw EXP_UNDER,EXP(%ebx)
jle L_underflow
L_exit_valid:
movl TAG_Valid,%eax
/* Convert the exponent to 80x87 form. */
addw EXTENDED_Ebias,EXP(%ebx)
andw $0x7fff,EXP(%ebx)
L_exit:
popl %ebx
leave
ret
L_zero:
movw $0,EXP(%ebx)
movl TAG_Zero,%eax
jmp L_exit
L_underflow:
/* Convert the exponent to 80x87 form. */
addw EXTENDED_Ebias,EXP(%ebx)
push %ebx
call arith_underflow
pop %ebx
jmp L_exit
L_overflow:
/* Convert the exponent to 80x87 form. */
addw EXTENDED_Ebias,EXP(%ebx)
push %ebx
call arith_overflow
pop %ebx
jmp L_exit
/* Normalise without reporting underflow or overflow */
ENTRY(FPU_normalize_nuo)
pushl %ebp
movl %esp,%ebp
pushl %ebx
movl PARAM1,%ebx
movl SIGH(%ebx),%edx
movl SIGL(%ebx),%eax
orl %edx,%edx /* ms bits */
js L_exit_nuo_valid /* Already normalized */
jnz L_nuo_shift_1 /* Shift left 1 - 31 bits */
orl %eax,%eax
jz L_exit_nuo_zero /* The contents are zero */
movl %eax,%edx
xorl %eax,%eax
subw $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
subw %cx,EXP(%ebx) /* This can cause an underflow */
movl %edx,SIGH(%ebx)
movl %eax,SIGL(%ebx)
L_exit_nuo_valid:
movl TAG_Valid,%eax
popl %ebx
leave
ret
L_exit_nuo_zero:
movl TAG_Zero,%eax
movw EXP_UNDER,EXP(%ebx)
popl %ebx
leave
ret
