target/arm: Ignore float_flag_input_denormal from fp_status_f16

When FZ is set, input_denormal exceptions are recognized, but this does
not happen with FZ16.  The softfloat code has no way to distinguish
these bits and will raise such exceptions into fp_status_f16.flags,
so ignore them when computing the accumulated flags.

Cc: qemu-stable@nongnu.org (3.0.1)
Reported-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Tested-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Message-id: 20180810193129.1556-3-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
(cherry picked from commit 19062c169e5bcdda3d60df9161228e107bf0f96e)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/target/arm/helper.c b/target/arm/helper.c
index c2287c76e596334ad3d3a3d26c88dd707e44cd38..991b077e8fbd9da6a1fc0bb9c887e861288f1e55 100644 (file)
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -11283,9 +11283,13 @@ uint32_t HELPER(vfp_get_fpscr)(CPUARMState *env)
     fpscr = (env->vfp.xregs[ARM_VFP_FPSCR] & 0xffc8ffff)
             | (env->vfp.vec_len << 16)
             | (env->vfp.vec_stride << 20);
+
     i = get_float_exception_flags(&env->vfp.fp_status);
     i |= get_float_exception_flags(&env->vfp.standard_fp_status);
-    i |= get_float_exception_flags(&env->vfp.fp_status_f16);
+    /* FZ16 does not generate an input denormal exception.  */
+    i |= (get_float_exception_flags(&env->vfp.fp_status_f16)
+          & ~float_flag_input_denormal);
+
     fpscr |= vfp_exceptbits_from_host(i);
     return fpscr;
 }