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: Paul 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: Ralf Baechle <ralf@linux-mips.org>

arch/mips/math-emu/Makefile

@@ -4,7 +4,7 @@
 
 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_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_tint.o sp_fint.o sp_maddf.o sp_2008class.o sp_fmin.o sp_fmax.o \
 	   dsemul.o

arch/mips/math-emu/dp_maddf.c

@@ -14,8 +14,12 @@
 
 #include "ieee754dp.h"
 
-union ieee754dp ieee754dp_maddf(union ieee754dp z, union ieee754dp x,
-				union ieee754dp y)
+enum maddf_flags {
+	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 rs;
@@ -154,6 +158,8 @@ union ieee754dp ieee754dp_maddf(union ieee754dp z, union ieee754dp x,
 
 	re = xe + ye;
 	rs = xs ^ ys;
+	if (flags & maddf_negate_product)
+		rs ^= 1;
 
 	/* shunt to top of word */
 	xm <<= 64 - (DP_FBITS + 1);
@@ -263,3 +269,15 @@ union ieee754dp ieee754dp_maddf(union ieee754dp z, union ieee754dp x,
 
 	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);
+}

arch/mips/math-emu/dp_msubf.c

-/*
- * 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);
-}