[PATCH] ARM: 2841/1: Fix VFP +/-0 case for doubles addition

Patch from Catalin Marinas

The IEEE 754 standard specifies that the result of (x - x), where x is
a valid number, should be -0 if the rounding mode is towards minus
infinity or +0 otherwise.
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/vfp/vfpdouble.c

@@ -770,6 +770,9 @@ vfp_double_add(struct vfp_double *vdd, struct vfp_double *vdn,
 		if ((s64)m_sig < 0) {
 			vdd->sign = vfp_sign_negate(vdd->sign);
 			m_sig = -m_sig;
+		} else if (m_sig == 0) {
+			vdd->sign = (fpscr & FPSCR_RMODE_MASK) ==
+				      FPSCR_ROUND_MINUSINF ? 0x8000 : 0;
 		}
 	} else {
 		m_sig += vdn->significand;