MIPS: math-emu: Add IEEE Std 754-2008 ABS.fmt and NEG.fmt emulation

Implement IEEE Std 754-2008 non-arithmetic ABS.fmt and NEG.fmt emulation
wired to the state of the FCSR.ABS2008 bit.  In the non-arithmetic mode
the sign bit is altered according to the operation requested regardless
of the datum encoded in the input operand, no other bits are changed,
the resulting bit pattern is written to the output operand and no
exception is ever signalled.

Signed-off-by: Maciej W. Rozycki <macro@imgtec.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Fortune <Matthew.Fortune@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/11476/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/math-emu/dp_simple.c

@@ -23,27 +23,39 @@
 
 union ieee754dp ieee754dp_neg(union ieee754dp x)
 {
-	unsigned int oldrm;
 	union ieee754dp y;
 
-	oldrm = ieee754_csr.rm;
-	ieee754_csr.rm = FPU_CSR_RD;
-	y = ieee754dp_sub(ieee754dp_zero(0), x);
-	ieee754_csr.rm = oldrm;
+	if (ieee754_csr.abs2008) {
+		y = x;
+		DPSIGN(y) = !DPSIGN(x);
+	} else {
+		unsigned int oldrm;
+
+		oldrm = ieee754_csr.rm;
+		ieee754_csr.rm = FPU_CSR_RD;
+		y = ieee754dp_sub(ieee754dp_zero(0), x);
+		ieee754_csr.rm = oldrm;
+	}
 	return y;
 }
 
 union ieee754dp ieee754dp_abs(union ieee754dp x)
 {
-	unsigned int oldrm;
 	union ieee754dp y;
 
-	oldrm = ieee754_csr.rm;
-	ieee754_csr.rm = FPU_CSR_RD;
-	if (DPSIGN(x))
-		y = ieee754dp_sub(ieee754dp_zero(0), x);
-	else
-		y = ieee754dp_add(ieee754dp_zero(0), x);
-	ieee754_csr.rm = oldrm;
+	if (ieee754_csr.abs2008) {
+		y = x;
+		DPSIGN(y) = 0;
+	} else {
+		unsigned int oldrm;
+
+		oldrm = ieee754_csr.rm;
+		ieee754_csr.rm = FPU_CSR_RD;
+		if (DPSIGN(x))
+			y = ieee754dp_sub(ieee754dp_zero(0), x);
+		else
+			y = ieee754dp_add(ieee754dp_zero(0), x);
+		ieee754_csr.rm = oldrm;
+	}
 	return y;
 }

arch/mips/math-emu/sp_simple.c

@@ -23,27 +23,39 @@
 
 union ieee754sp ieee754sp_neg(union ieee754sp x)
 {
-	unsigned int oldrm;
 	union ieee754sp y;
 
-	oldrm = ieee754_csr.rm;
-	ieee754_csr.rm = FPU_CSR_RD;
-	y = ieee754sp_sub(ieee754sp_zero(0), x);
-	ieee754_csr.rm = oldrm;
+	if (ieee754_csr.abs2008) {
+		y = x;
+		SPSIGN(y) = !SPSIGN(x);
+	} else {
+		unsigned int oldrm;
+
+		oldrm = ieee754_csr.rm;
+		ieee754_csr.rm = FPU_CSR_RD;
+		y = ieee754sp_sub(ieee754sp_zero(0), x);
+		ieee754_csr.rm = oldrm;
+	}
 	return y;
 }
 
 union ieee754sp ieee754sp_abs(union ieee754sp x)
 {
-	unsigned int oldrm;
 	union ieee754sp y;
 
-	oldrm = ieee754_csr.rm;
-	ieee754_csr.rm = FPU_CSR_RD;
-	if (SPSIGN(x))
-		y = ieee754sp_sub(ieee754sp_zero(0), x);
-	else
-		y = ieee754sp_add(ieee754sp_zero(0), x);
-	ieee754_csr.rm = oldrm;
+	if (ieee754_csr.abs2008) {
+		y = x;
+		SPSIGN(y) = 0;
+	} else {
+		unsigned int oldrm;
+
+		oldrm = ieee754_csr.rm;
+		ieee754_csr.rm = FPU_CSR_RD;
+		if (SPSIGN(x))
+			y = ieee754sp_sub(ieee754sp_zero(0), x);
+		else
+			y = ieee754sp_add(ieee754sp_zero(0), x);
+		ieee754_csr.rm = oldrm;
+	}
 	return y;
 }