Commit d728f670 authored by Paul Burton's avatar Paul Burton Committed by Ralf Baechle

MIPS: math-emu: Unify ieee754dp_m{add,sub}f

The code for emulating MIPSr6 madd.d & msub.d instructions has
previously been implemented as 2 different functions, namely
ieee754dp_maddf & ieee754dp_msubf. The difference in behaviour of these
2 instructions is merely the sign of the product, so we can easily share
the code implementing them. Do this for the double precision variant,
removing the original ieee754dp_msubf in favor of reusing the code from
ieee754dp_maddf.
Signed-off-by: default avatarPaul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13155/Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
parent 6162051e
...@@ -4,7 +4,7 @@ ...@@ -4,7 +4,7 @@
obj-y += cp1emu.o ieee754dp.o ieee754sp.o ieee754.o \ obj-y += cp1emu.o ieee754dp.o ieee754sp.o ieee754.o \
dp_div.o dp_mul.o dp_sub.o dp_add.o dp_fsp.o dp_cmp.o dp_simple.o \ dp_div.o dp_mul.o dp_sub.o dp_add.o dp_fsp.o dp_cmp.o dp_simple.o \
dp_tint.o dp_fint.o dp_maddf.o dp_msubf.o dp_2008class.o dp_fmin.o dp_fmax.o \ dp_tint.o dp_fint.o dp_maddf.o dp_2008class.o dp_fmin.o dp_fmax.o \
sp_div.o sp_mul.o sp_sub.o sp_add.o sp_fdp.o sp_cmp.o sp_simple.o \ sp_div.o sp_mul.o sp_sub.o sp_add.o sp_fdp.o sp_cmp.o sp_simple.o \
sp_tint.o sp_fint.o sp_maddf.o sp_2008class.o sp_fmin.o sp_fmax.o \ sp_tint.o sp_fint.o sp_maddf.o sp_2008class.o sp_fmin.o sp_fmax.o \
dsemul.o dsemul.o
......
...@@ -14,8 +14,12 @@ ...@@ -14,8 +14,12 @@
#include "ieee754dp.h" #include "ieee754dp.h"
union ieee754dp ieee754dp_maddf(union ieee754dp z, union ieee754dp x, enum maddf_flags {
union ieee754dp y) maddf_negate_product = 1 << 0,
};
static union ieee754dp _dp_maddf(union ieee754dp z, union ieee754dp x,
union ieee754dp y, enum maddf_flags flags)
{ {
int re; int re;
int rs; int rs;
...@@ -154,6 +158,8 @@ union ieee754dp ieee754dp_maddf(union ieee754dp z, union ieee754dp x, ...@@ -154,6 +158,8 @@ union ieee754dp ieee754dp_maddf(union ieee754dp z, union ieee754dp x,
re = xe + ye; re = xe + ye;
rs = xs ^ ys; rs = xs ^ ys;
if (flags & maddf_negate_product)
rs ^= 1;
/* shunt to top of word */ /* shunt to top of word */
xm <<= 64 - (DP_FBITS + 1); xm <<= 64 - (DP_FBITS + 1);
...@@ -263,3 +269,15 @@ union ieee754dp ieee754dp_maddf(union ieee754dp z, union ieee754dp x, ...@@ -263,3 +269,15 @@ union ieee754dp ieee754dp_maddf(union ieee754dp z, union ieee754dp x,
return ieee754dp_format(zs, ze, zm); return ieee754dp_format(zs, ze, zm);
} }
union ieee754dp ieee754dp_maddf(union ieee754dp z, union ieee754dp x,
union ieee754dp y)
{
return _dp_maddf(z, x, y, 0);
}
union ieee754dp ieee754dp_msubf(union ieee754dp z, union ieee754dp x,
union ieee754dp y)
{
return _dp_maddf(z, x, y, maddf_negate_product);
}
/*
* IEEE754 floating point arithmetic
* double precision: MSUB.f (Fused Multiply Subtract)
* MSUBF.fmt: FPR[fd] = FPR[fd] - (FPR[fs] x FPR[ft])
*
* MIPS floating point support
* Copyright (C) 2015 Imagination Technologies, Ltd.
* Author: Markos Chandras <markos.chandras@imgtec.com>
*
* This program is free software; you can distribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; version 2 of the License.
*/
#include "ieee754dp.h"
union ieee754dp ieee754dp_msubf(union ieee754dp z, union ieee754dp x,
union ieee754dp y)
{
int re;
int rs;
u64 rm;
unsigned lxm;
unsigned hxm;
unsigned lym;
unsigned hym;
u64 lrm;
u64 hrm;
u64 t;
u64 at;
int s;
COMPXDP;
COMPYDP;
u64 zm; int ze; int zs __maybe_unused; int zc;
EXPLODEXDP;
EXPLODEYDP;
EXPLODEDP(z, zc, zs, ze, zm)
FLUSHXDP;
FLUSHYDP;
FLUSHDP(z, zc, zs, ze, zm);
ieee754_clearcx();
switch (zc) {
case IEEE754_CLASS_SNAN:
ieee754_setcx(IEEE754_INVALID_OPERATION);
return ieee754dp_nanxcpt(z);
case IEEE754_CLASS_DNORM:
DPDNORMx(zm, ze);
/* QNAN is handled separately below */
}
switch (CLPAIR(xc, yc)) {
case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
return ieee754dp_nanxcpt(y);
case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
return ieee754dp_nanxcpt(x);
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
return y;
case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
return x;
/*
* Infinity handling
*/
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
if (zc == IEEE754_CLASS_QNAN)
return z;
ieee754_setcx(IEEE754_INVALID_OPERATION);
return ieee754dp_indef();
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
if (zc == IEEE754_CLASS_QNAN)
return z;
return ieee754dp_inf(xs ^ ys);
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
if (zc == IEEE754_CLASS_INF)
return ieee754dp_inf(zs);
/* Multiplication is 0 so just return z */
return z;
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
DPDNORMX;
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
if (zc == IEEE754_CLASS_QNAN)
return z;
else if (zc == IEEE754_CLASS_INF)
return ieee754dp_inf(zs);
DPDNORMY;
break;
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
if (zc == IEEE754_CLASS_QNAN)
return z;
else if (zc == IEEE754_CLASS_INF)
return ieee754dp_inf(zs);
DPDNORMX;
break;
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
if (zc == IEEE754_CLASS_QNAN)
return z;
else if (zc == IEEE754_CLASS_INF)
return ieee754dp_inf(zs);
/* fall through to real computations */
}
/* Finally get to do some computation */
/*
* Do the multiplication bit first
*
* rm = xm * ym, re = xe + ye basically
*
* At this point xm and ym should have been normalized.
*/
assert(xm & DP_HIDDEN_BIT);
assert(ym & DP_HIDDEN_BIT);
re = xe + ye;
rs = xs ^ ys;
/* shunt to top of word */
xm <<= 64 - (DP_FBITS + 1);
ym <<= 64 - (DP_FBITS + 1);
/*
* Multiply 32 bits xm, ym to give high 32 bits rm with stickness.
*/
/* 32 * 32 => 64 */
#define DPXMULT(x, y) ((u64)(x) * (u64)y)
lxm = xm;
hxm = xm >> 32;
lym = ym;
hym = ym >> 32;
lrm = DPXMULT(lxm, lym);
hrm = DPXMULT(hxm, hym);
t = DPXMULT(lxm, hym);
at = lrm + (t << 32);
hrm += at < lrm;
lrm = at;
hrm = hrm + (t >> 32);
t = DPXMULT(hxm, lym);
at = lrm + (t << 32);
hrm += at < lrm;
lrm = at;
hrm = hrm + (t >> 32);
rm = hrm | (lrm != 0);
/*
* Sticky shift down to normal rounding precision.
*/
if ((s64) rm < 0) {
rm = (rm >> (64 - (DP_FBITS + 1 + 3))) |
((rm << (DP_FBITS + 1 + 3)) != 0);
re++;
} else {
rm = (rm >> (64 - (DP_FBITS + 1 + 3 + 1))) |
((rm << (DP_FBITS + 1 + 3 + 1)) != 0);
}
assert(rm & (DP_HIDDEN_BIT << 3));
/* And now the subtraction */
/* flip sign of r and handle as add */
rs ^= 1;
assert(zm & DP_HIDDEN_BIT);
/*
* Provide guard,round and stick bit space.
*/
zm <<= 3;
if (ze > re) {
/*
* Have to shift y fraction right to align.
*/
s = ze - re;
rm = XDPSRS(rm, s);
re += s;
} else if (re > ze) {
/*
* Have to shift x fraction right to align.
*/
s = re - ze;
zm = XDPSRS(zm, s);
ze += s;
}
assert(ze == re);
assert(ze <= DP_EMAX);
if (zs == rs) {
/*
* Generate 28 bit result of adding two 27 bit numbers
* leaving result in xm, xs and xe.
*/
zm = zm + rm;
if (zm >> (DP_FBITS + 1 + 3)) { /* carry out */
zm = XDPSRS1(zm);
ze++;
}
} else {
if (zm >= rm) {
zm = zm - rm;
} else {
zm = rm - zm;
zs = rs;
}
if (zm == 0)
return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD);
/*
* Normalize to rounding precision.
*/
while ((zm >> (DP_FBITS + 3)) == 0) {
zm <<= 1;
ze--;
}
}
return ieee754dp_format(zs, ze, zm);
}
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