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.file "reg_u_mul.S"
/*---------------------------------------------------------------------------+
| reg_u_mul.S |
| |
| Core multiplication routine |
| |
| Copyright (C) 1992,1993,1995,1997 |
| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
| E-mail billm@suburbia.net |
| |
| |
+---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------+
| Basic multiplication routine. |
| Does not check the resulting exponent for overflow/underflow |
| |
| FPU_u_mul(FPU_REG *a, FPU_REG *b, FPU_REG *c, unsigned int cw); |
| |
| Internal working is at approx 128 bits. |
| Result is rounded to nearest 53 or 64 bits, using "nearest or even". |
+---------------------------------------------------------------------------*/
#include "exception.h"
#include "fpu_emu.h"
#include "control_w.h"
#ifndef NON_REENTRANT_FPU
/* Local storage on the stack: */
#define FPU_accum_0 -4(%ebp) /* ms word */
#define FPU_accum_1 -8(%ebp)
#else
/* Local storage in a static area: */
.data
.align 4,0
FPU_accum_0:
.long 0
FPU_accum_1:
.long 0
#endif /* NON_REENTRANT_FPU */
.text
ENTRY(FPU_u_mul)
pushl %ebp
movl %esp,%ebp
#ifndef NON_REENTRANT_FPU
subl $8,%esp
#endif /* NON_REENTRANT_FPU */
pushl %esi
pushl %edi
pushl %ebx
movl PARAM1,%esi
movl PARAM2,%edi
#ifdef PARANOID
testl $0x80000000,SIGH(%esi)
jz L_bugged
testl $0x80000000,SIGH(%edi)
jz L_bugged
#endif /* PARANOID */
xorl %ecx,%ecx
xorl %ebx,%ebx
movl SIGL(%esi),%eax
mull SIGL(%edi)
movl %eax,FPU_accum_0
movl %edx,FPU_accum_1
movl SIGL(%esi),%eax
mull SIGH(%edi)
addl %eax,FPU_accum_1
adcl %edx,%ebx
/* adcl $0,%ecx // overflow here is not possible */
movl SIGH(%esi),%eax
mull SIGL(%edi)
addl %eax,FPU_accum_1
adcl %edx,%ebx
adcl $0,%ecx
movl SIGH(%esi),%eax
mull SIGH(%edi)
addl %eax,%ebx
adcl %edx,%ecx
/* Get the sum of the exponents. */
movl PARAM6,%eax
subl EXP_BIAS-1,%eax
/* Two denormals can cause an exponent underflow */
cmpl EXP_WAY_UNDER,%eax
jg Exp_not_underflow
/* Set to a really low value allow correct handling */
movl EXP_WAY_UNDER,%eax
Exp_not_underflow:
/* Have now finished with the sources */
movl PARAM3,%edi /* Point to the destination */
movw %ax,EXP(%edi)
/* Now make sure that the result is normalized */
testl $0x80000000,%ecx
jnz LResult_Normalised
/* Normalize by shifting left one bit */
shll $1,FPU_accum_0
rcll $1,FPU_accum_1
rcll $1,%ebx
rcll $1,%ecx
decw EXP(%edi)
LResult_Normalised:
movl FPU_accum_0,%eax
movl FPU_accum_1,%edx
orl %eax,%eax
jz L_extent_zero
orl $1,%edx
L_extent_zero:
movl %ecx,%eax
jmp fpu_reg_round
#ifdef PARANOID
L_bugged:
pushl EX_INTERNAL|0x205
call EXCEPTION
pop %ebx
jmp L_exit
L_exit:
popl %ebx
popl %edi
popl %esi
leave
ret
#endif /* PARANOID */
|
