softfloat: Fix float64_to_uint32

The float64_to_uint32 has several flaws:

 - for numbers between 2**32 and 2**64, the inexact exception flag
   may get incorrectly set.  In this case, only the invalid flag
   should be set.

       test pattern: 425F81378DC0CD1F / 0x1.f81378dc0cd1fp+38

 - for numbers between 2**63 and 2**64, incorrect results may
   be produced:

       test pattern: 43EAAF73F1F0B8BD / 0x1.aaf73f1f0b8bdp+63

This patch re-implements float64_to_uint32 to re-use the
float64_to_uint64 routine (instead of float64_to_int64).  For the
saturation case, we ignore any flags which the conversion routine
has set and raise only the invalid flag.

This contribution can be licensed under either the softfloat-2a or -2b
license.

Signed-off-by: Tom Musta <tommusta@gmail.com>
Message-id: 1387397961-4894-5-git-send-email-tommusta@gmail.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>

1 files changed, 7 insertions, 8 deletions

diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index f782c24ef2..e68a87b6da 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -6650,19 +6650,18 @@ uint_fast16_t float32_to_uint16_round_to_zero(float32 a STATUS_PARAM)
 
 uint32 float64_to_uint32( float64 a STATUS_PARAM )
 {
-    int64_t v;
+    uint64_t v;
     uint32 res;
+    int old_exc_flags = get_float_exception_flags(status);
 
-    v = float64_to_int64(a STATUS_VAR);
-    if (v < 0) {
-        res = 0;
-        float_raise( float_flag_invalid STATUS_VAR);
-    } else if (v > 0xffffffff) {
+    v = float64_to_uint64(a STATUS_VAR);
+    if (v > 0xffffffff) {
         res = 0xffffffff;
-        float_raise( float_flag_invalid STATUS_VAR);
     } else {
-        res = v;
+        return v;
     }
+    set_float_exception_flags(old_exc_flags, status);
+    float_raise(float_flag_invalid STATUS_VAR);
     return res;
 }