[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: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/vfp/vfpdouble.c b/arch/arm/vfp/vfpdouble.c
index b801cd6..9b367a6 100644 (file)
--- a/arch/arm/vfp/vfpdouble.c
+++ b/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;