dba4d32f68
ieee fp support by Ian Dall, NetBSD/pc532 integration by Matthias Pfaller. Includes setjmp/longjmp added to locore.s.
430 lines
11 KiB
C
430 lines
11 KiB
C
/* $NetBSD: ieee_subnormal.c,v 1.1 1996/04/04 06:36:30 phil Exp $ */
|
|
|
|
/*
|
|
* IEEE floating point support for NS32081 and NS32381 fpus.
|
|
* Copyright (c) 1995 Ian Dall
|
|
* All Rights Reserved.
|
|
*
|
|
* Permission to use, copy, modify and distribute this software and its
|
|
* documentation is hereby granted, provided that both the copyright
|
|
* notice and this permission notice appear in all copies of the
|
|
* software, derivative works or modified versions, and any portions
|
|
* thereof, and that both notices appear in supporting documentation.
|
|
*
|
|
* IAN DALL ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" CONDITION.
|
|
* IAN DALL DISCLAIMS ANY LIABILITY OF ANY KIND FOR ANY DAMAGES
|
|
* WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
|
|
*/
|
|
/*
|
|
* File: ieee_subnormal.c
|
|
* Author: Ian Dall
|
|
* Date: November 1995
|
|
*
|
|
* Handle operations which generated underflow traps. Subnormal
|
|
* (denormalized numbers) are generated as required.
|
|
*
|
|
* HISTORY
|
|
* 14-Dec-95 Ian Dall (Ian.Dall@dsto.defence.gov.au)
|
|
* First release.
|
|
*
|
|
*/
|
|
#include "ieee_internal.h"
|
|
#include <machine/psl.h>
|
|
|
|
/* Return bit pos numbered from lsb 0 to 31. Returns 31 if no bit is set */
|
|
static int find_msb(unsigned int t) {
|
|
static const int b_mask[] = {
|
|
0xffff0000,
|
|
0xff00ff00,
|
|
0xf0f0f0f0,
|
|
0xcccccccc,
|
|
0xaaaaaaaa };
|
|
int i;
|
|
int pos = 31;
|
|
int bit_incr = 16; /* Half no of bits in int */
|
|
for (i = 0; i < 5; i++, bit_incr /= 2) {
|
|
if(t & b_mask[i]) {
|
|
t &= b_mask[i];
|
|
}
|
|
else {
|
|
pos -= bit_incr;
|
|
t &= ~b_mask[i];
|
|
}
|
|
}
|
|
return pos;
|
|
}
|
|
|
|
static int leading_zeros(union t_conv *data)
|
|
{
|
|
unsigned int t;
|
|
if ((t = data->d_bits.mantissa)) {
|
|
return 19 - find_msb(t);
|
|
}
|
|
else if ((t = data->d_bits.mantissa2)) {
|
|
return 51 - find_msb(t);
|
|
}
|
|
else
|
|
return 52;
|
|
}
|
|
|
|
static void lshift_mantissa(union t_conv *data, int n)
|
|
{
|
|
unsigned long t[2];
|
|
t[1] = data->d_bits.mantissa;
|
|
t[0] = data->d_bits.mantissa2;
|
|
*(unsigned long long *) t <<= n;
|
|
data->d_bits.mantissa = t[1];
|
|
data->d_bits.mantissa2 = t[0];
|
|
}
|
|
|
|
|
|
static void rshift_mantissa(union t_conv *data, int n)
|
|
{
|
|
unsigned long t[2];
|
|
t[1] = data->d_bits.mantissa | 0x100000;
|
|
t[0] = data->d_bits.mantissa2;
|
|
*(unsigned long long *) t >>= n;
|
|
data->d_bits.mantissa = t[1];
|
|
data->d_bits.mantissa2 = t[0];
|
|
}
|
|
|
|
/* After this, the data is a normal double and the returned value is
|
|
* such that:
|
|
* union t_conv t;
|
|
* t = *data;
|
|
* norm = normalize(&t);
|
|
* 2**norm * t.d == data->d;
|
|
*
|
|
* Assume data is not already normalized.
|
|
*/
|
|
int ieee_normalize(union t_conv *data)
|
|
{
|
|
int norm;
|
|
if(data->d_bits.exp != 0)
|
|
return 0;
|
|
norm = leading_zeros(data) + 1; /* plus one for the implied bit */
|
|
data->d_bits.exp = 1;
|
|
lshift_mantissa(data, norm);
|
|
return -norm;
|
|
}
|
|
|
|
/* Divide by 2**n producing a denormalized no if necessary */
|
|
static void denormalize(union t_conv *data, int n)
|
|
{
|
|
int exp = data->d_bits.exp;
|
|
if(exp > n)
|
|
exp -= n;
|
|
else if (exp <= n) {
|
|
rshift_mantissa(data, n - exp + 1); /* plus 1 for the implied bit */
|
|
exp = 0;
|
|
}
|
|
data->d_bits.exp = exp;
|
|
}
|
|
|
|
static int scale_and_check(union t_conv *d, int scale)
|
|
{
|
|
int exp;
|
|
exp = d->d_bits.exp - scale;
|
|
if(exp >= 0x7ff) {
|
|
/* Overflow */
|
|
d->d_bits.exp = 0x7ff;
|
|
d->d_bits.mantissa = 0;
|
|
d->d_bits.mantissa2 = 0; /* XXX sig */
|
|
return FPC_TT_OVFL;
|
|
}
|
|
if(exp <= 0) {
|
|
/* Underflow */
|
|
denormalize(d, scale); /* XXX sig */
|
|
return FPC_TT_UNDFL;
|
|
}
|
|
d->d_bits.exp = exp;
|
|
return FPC_TT_NONE;
|
|
}
|
|
|
|
|
|
/* Add two doubles, not caring if one or both is a de-norm.
|
|
* Strategy: First scale and normalize operands so the addition
|
|
* can't overflow or underflow, then do a normal floating point
|
|
* addition, then scale back and possibly denormalize.
|
|
*/
|
|
int ieee_add(double data1, double *data2)
|
|
{
|
|
union t_conv d1 = (union t_conv) data1;
|
|
union t_conv *d2 = (union t_conv *) data2;
|
|
int scale;
|
|
int norm1 = ieee_normalize(&d1);
|
|
int norm2 = ieee_normalize(d2);
|
|
int exp1 = d1.d_bits.exp + norm1;
|
|
int exp2 = d2->d_bits.exp + norm2;
|
|
if(exp1 > exp2) {
|
|
scale = EXP_DBIAS - exp1;
|
|
exp1 = EXP_DBIAS;
|
|
exp2 += scale;
|
|
}
|
|
else {
|
|
scale = EXP_DBIAS - exp2;
|
|
exp2 = EXP_DBIAS;
|
|
exp1 += scale;
|
|
}
|
|
if(exp1 > 0) {
|
|
d1.d_bits.exp = exp1;
|
|
if (exp2 > 0) {
|
|
d2->d_bits.exp = exp2;
|
|
d2->d += d1.d;
|
|
}
|
|
else {
|
|
d2->d = d1.d;
|
|
}
|
|
}
|
|
else {
|
|
d2->d_bits.exp = exp2;
|
|
}
|
|
return scale_and_check(d2, scale);
|
|
}
|
|
|
|
/* Multiply two doubles, not caring if one or both is a de-norm.
|
|
* Strategy: First scale and normalize operands so the multiplication
|
|
* can't overflow or underflow, then do a normal floating point
|
|
* addition, then scale back and possibly denormalize.
|
|
*/
|
|
int ieee_mul(double data1, double *data2)
|
|
{
|
|
union t_conv d1 = (union t_conv) data1;
|
|
union t_conv *d2 = (union t_conv *) data2;
|
|
int scale;
|
|
int norm1 = ieee_normalize(&d1);
|
|
int norm2 = ieee_normalize(d2);
|
|
int exp1 = d1.d_bits.exp + norm1;
|
|
int exp2 = d2->d_bits.exp + norm2;
|
|
d1.d_bits.exp = EXP_DBIAS; /* Add EXP_DBIAS - exp1 */
|
|
d2->d_bits.exp = EXP_DBIAS;
|
|
d2->d *= d1.d;
|
|
scale = EXP_DBIAS - exp1 + EXP_DBIAS - exp2;
|
|
return scale_and_check(d2, scale);
|
|
}
|
|
|
|
/* Divide d2 by d1, not caring if one or both is a de-norm.
|
|
* Strategy: First scale and normalize operands so the division
|
|
* can't overflow or underflow, then do a normal floating point
|
|
* division, then scale back and possibly denormalize.
|
|
*/
|
|
int ieee_div(double data1, double *data2)
|
|
{
|
|
union t_conv d1 = (union t_conv) data1;
|
|
union t_conv *d2 = (union t_conv *) data2;
|
|
int scale;
|
|
int norm1 = ieee_normalize(&d1);
|
|
int norm2 = ieee_normalize(d2);
|
|
int exp1 = d1.d_bits.exp + norm1;
|
|
int exp2 = d2->d_bits.exp + norm2;
|
|
d1.d_bits.exp = EXP_DBIAS; /* Add EXP_DBIAS - exp1 */
|
|
d2->d_bits.exp = EXP_DBIAS;
|
|
d2->d /= d1.d;
|
|
scale = exp1 - exp2;
|
|
return scale_and_check(d2, scale);
|
|
}
|
|
|
|
/* Add mul-add three doubles d1 * d2 + d3 -> d3, not caring if any a de-norm.
|
|
* Strategy: First scale and normalize operands so the operations
|
|
* can't overflow or underflow, then do a normal floating point operation
|
|
* addition, then scale back and possibly denormalize.
|
|
*/
|
|
int ieee_dot(double data1, double data2, double *data3)
|
|
{
|
|
union t_conv d1 = (union t_conv) data1;
|
|
union t_conv d2 = (union t_conv) data2;
|
|
union t_conv *d3 = (union t_conv *) data3;
|
|
int scale;
|
|
int norm1 = ieee_normalize(&d1);
|
|
int norm2 = ieee_normalize(&d2);
|
|
int norm3 = ieee_normalize(d3);
|
|
int exp1 = d1.d_bits.exp + norm1;
|
|
int exp2 = d2.d_bits.exp + norm2;
|
|
int exp3 = d3->d_bits.exp + norm3;
|
|
int exp_prod = exp1 + exp2;
|
|
if(exp_prod > exp3) {
|
|
scale = EXP_DBIAS + EXP_DBIAS - exp_prod;
|
|
exp1 = EXP_DBIAS; /* Add EXP_DBIAS - exp1 */
|
|
exp2 = EXP_DBIAS;
|
|
exp3 += scale;
|
|
}
|
|
else {
|
|
scale = EXP_DBIAS - exp3;
|
|
exp3 = EXP_DBIAS;
|
|
exp1 = (exp_prod + scale)/2;
|
|
exp2 = exp_prod + scale - exp1;
|
|
}
|
|
|
|
if(exp1 > 0 && exp2 > 0) {
|
|
d1.d_bits.exp = exp1;
|
|
d2.d_bits.exp = exp2;
|
|
if(exp3 > 0) {
|
|
d3->d_bits.exp = exp3;
|
|
d3->d += d1.d * d2.d;
|
|
}
|
|
else {
|
|
d3->d = d1.d * d2.d;
|
|
}
|
|
}
|
|
else {
|
|
d3->d_bits.exp = exp3;
|
|
}
|
|
return scale_and_check(d3, scale);
|
|
}
|
|
|
|
/* Compare the magnitude of two ops.
|
|
* return: 1 |op1| > |op2|
|
|
* -1 |op1| < |op2|
|
|
* 0 |op1| == |op2|
|
|
*/
|
|
static int u_cmp(double data1, double data2)
|
|
{
|
|
union t_conv d1 = (union t_conv) data1;
|
|
union t_conv d2 = (union t_conv) data2;
|
|
int exp1 = d1.d_bits.exp;
|
|
int exp2 = d2.d_bits.exp;
|
|
if (exp1 > exp2)
|
|
return 1;
|
|
else if (exp1 < exp2)
|
|
return -1;
|
|
else if (d1.d_bits.mantissa > d2.d_bits.mantissa)
|
|
return 1;
|
|
else if (d1.d_bits.mantissa < d2.d_bits.mantissa)
|
|
return -1;
|
|
else if (d1.d_bits.mantissa2 > d2.d_bits.mantissa2)
|
|
return 1;
|
|
else if (d1.d_bits.mantissa2 < d2.d_bits.mantissa2)
|
|
return -1;
|
|
else
|
|
return 0;
|
|
}
|
|
|
|
void ieee_cmp(double data1, double data2, state *state)
|
|
{
|
|
union t_conv d1 = (union t_conv) data1;
|
|
union t_conv d2 = (union t_conv) data2;
|
|
int sign1 = d1.d_bits.sign;
|
|
int sign2 = d2.d_bits.sign;
|
|
state->PSR &= ~(PSR_N | PSR_Z | PSR_L);
|
|
switch(sign2 * 2 + sign1) {
|
|
case 2: /* op2 is negative op1 is positive */
|
|
state->PSR |= PSR_N;
|
|
break;
|
|
case 1: /* op2 is positive op1 is negative */
|
|
break;
|
|
case 0: /* Both ops same sign */
|
|
case 3:
|
|
{
|
|
int cmp = u_cmp(d1.d, d2.d);
|
|
if(sign1)
|
|
cmp *= -1;
|
|
if(cmp > 0)
|
|
state->PSR |= PSR_N;
|
|
else if (cmp == 0)
|
|
state->PSR |= PSR_Z;
|
|
}
|
|
break;
|
|
}
|
|
return;
|
|
}
|
|
|
|
|
|
int ieee_scalb(double data1, double *data2)
|
|
{
|
|
union t_conv d1 = (union t_conv) data1;
|
|
union t_conv *d2 = (union t_conv *) data2;
|
|
int exp2 = d2->d_bits.exp - EXP_DBIAS;
|
|
int n;
|
|
if (exp2 > 16) {
|
|
*d2 = infty;
|
|
d2->d_bits.sign = d1.d_bits.sign;
|
|
return FPC_TT_OVFL;
|
|
}
|
|
else if (exp2 < -16) {
|
|
d2->d = 0.0;
|
|
d2->d_bits.sign = d1.d_bits.sign;
|
|
return FPC_TT_OVFL;
|
|
}
|
|
n = d2->d;
|
|
*d2 = d1;
|
|
return scale_and_check(d2, n);
|
|
}
|
|
|
|
/* With no trap, hardware produces zero, which is fast but not
|
|
* strictly correct. We should always have the hardware trap bit set
|
|
* and generate denormalized numbers by simulation unless the user
|
|
* indicates via the FPC_UNDE flag they want to handle it. */
|
|
|
|
int ieee_undfl(struct operand *op1, struct operand *op2,
|
|
struct operand *f0_op, int xopcode, state *state)
|
|
{
|
|
unsigned int fsr = state->FSR;
|
|
int user_trap = FPC_TT_NONE;
|
|
DP(1, "Underflow trap: xopcode = 0x%x\n", xopcode);
|
|
if (fsr & FPC_UNDE) {
|
|
user_trap = FPC_TT_UNDFL;
|
|
}
|
|
else {
|
|
user_trap = FPC_TT_NONE;
|
|
/* Calculate correct denormal output. The easiest way is to
|
|
* prescale the operands so they won't underflow, then use the
|
|
* hardware operation, then post scale.
|
|
*/
|
|
|
|
/* The exact sematics are a bit tricky. Apparently, we should only
|
|
* set flag if we underflowed *and* there was loss of precision
|
|
* For now, just set the flag always XXX
|
|
*/
|
|
fsr |= FPC_UF;
|
|
|
|
switch(xopcode) {
|
|
case NEGF:
|
|
op1->data.d_bits.sign ^= 1;
|
|
/* Fall through */
|
|
case MOVF:
|
|
case MOVLF:
|
|
case MOVFL:
|
|
op2->data = op1->data;
|
|
break;
|
|
case CMPF:
|
|
ieee_cmp(op1->data.d, op2->data.d, state);
|
|
break;
|
|
case SUBF:
|
|
op1->data.d_bits.sign ^= 1;
|
|
/* Fall through */
|
|
case ADDF:
|
|
user_trap = ieee_add(op1->data.d, &op2->data.d);
|
|
break;
|
|
case MULF:
|
|
user_trap = ieee_mul(op1->data.d, &op2->data.d);
|
|
break;
|
|
case DIVF:
|
|
user_trap = ieee_div(op1->data.d, &op2->data.d);
|
|
break;
|
|
case ROUNDFI:
|
|
case TRUNCFI:
|
|
case FLOORFI:
|
|
op2->data.i = 0;
|
|
break;
|
|
case SCALBF:
|
|
user_trap = ieee_scalb(op1->data.d, &op2->data.d);
|
|
break;
|
|
case LOGBF:
|
|
op2->data.d = 0.0;
|
|
break;
|
|
case DOTF:
|
|
user_trap = ieee_dot(op1->data.d, op2->data.d, &f0_op->data.d);
|
|
break;
|
|
case POLYF:
|
|
{
|
|
union t_conv t = op2->data;
|
|
user_trap = ieee_dot(f0_op->data.d, op1->data.d, &t.d);
|
|
f0_op->data = t;
|
|
}
|
|
break;
|
|
}
|
|
}
|
|
state->FSR = fsr;
|
|
return user_trap;
|
|
}
|