MIPS: math-emu: Unify ieee754sp_m{add,sub}f

The code for emulating MIPSr6 madd.s & msub.s instructions has
previously been implemented as 2 different functions, namely
ieee754sp_maddf & ieee754sp_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 single precision variant,
removing the original ieee754sp_msubf in favor of reusing the code from
ieee754sp_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/13154/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/math-emu/sp_maddf.c

@@ -14,8 +14,12 @@
 
 #include "ieee754sp.h"
 
-union ieee754sp ieee754sp_maddf(union ieee754sp z, union ieee754sp x,
-				union ieee754sp y)
+enum maddf_flags {
+	maddf_negate_product	= 1 << 0,
+};
+
+static union ieee754sp _sp_maddf(union ieee754sp z, union ieee754sp x,
+				 union ieee754sp y, enum maddf_flags flags)
 {
 	int re;
 	int rs;
@@ -154,6 +158,8 @@ union ieee754sp ieee754sp_maddf(union ieee754sp z, union ieee754sp x,
 
 	re = xe + ye;
 	rs = xs ^ ys;
+	if (flags & maddf_negate_product)
+		rs ^= 1;
 
 	/* shunt to top of word */
 	xm <<= 32 - (SP_FBITS + 1);
@@ -253,3 +259,15 @@ union ieee754sp ieee754sp_maddf(union ieee754sp z, union ieee754sp x,
 	}
 	return ieee754sp_format(zs, ze, zm);
 }
+
+union ieee754sp ieee754sp_maddf(union ieee754sp z, union ieee754sp x,
+				union ieee754sp y)
+{
+	return _sp_maddf(z, x, y, 0);
+}
+
+union ieee754sp ieee754sp_msubf(union ieee754sp z, union ieee754sp x,
+				union ieee754sp y)
+{
+	return _sp_maddf(z, x, y, maddf_negate_product);
+}