softfloat: Add float32_to_uint64()

This patch adds the float32_to_uint64() routine, which converts a
32-bit floating point number to an unsigned 64 bit number.

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

V2: Reduced patch to just this single routine per feedback from Peter
Maydell.

V4: Now passing sign to roundAndPackUint64()

Signed-off-by: Tom Musta <tommusta@gmail.com>
Message-id: 1387397961-4894-3-git-send-email-tommusta@gmail.com

PMM notes:
 * signed NaNs again
 * not convinced about handling of negative-but-round-to-zero inputs

2 files changed, 46 insertions, 0 deletions

diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index 1af6ca56e5..af371649cd 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -1558,6 +1558,51 @@ int64 float32_to_int64( float32 a STATUS_PARAM )
 
 /*----------------------------------------------------------------------------
 | Returns the result of converting the single-precision floating-point value
+| `a' to the 64-bit unsigned integer format.  The conversion is
+| performed according to the IEC/IEEE Standard for Binary Floating-Point
+| Arithmetic---which means in particular that the conversion is rounded
+| according to the current rounding mode.  If `a' is a NaN, the largest
+| unsigned integer is returned.  Otherwise, if the conversion overflows, the
+| largest unsigned integer is returned.  If the 'a' is negative, zero is
+| returned.
+*----------------------------------------------------------------------------*/
+
+uint64 float32_to_uint64(float32 a STATUS_PARAM)
+{
+    flag aSign;
+    int_fast16_t aExp, shiftCount;
+    uint32_t aSig;
+    uint64_t aSig64, aSigExtra;
+    a = float32_squash_input_denormal(a STATUS_VAR);
+
+    aSig = extractFloat32Frac(a);
+    aExp = extractFloat32Exp(a);
+    aSign = extractFloat32Sign(a);
+    if (aSign) {
+        if (aExp) {
+            float_raise(float_flag_invalid STATUS_VAR);
+        } else if (aSig) { /* negative denormalized */
+            float_raise(float_flag_inexact STATUS_VAR);
+        }
+        return 0;
+    }
+    shiftCount = 0xBE - aExp;
+    if (aExp) {
+        aSig |= 0x00800000;
+    }
+    if (shiftCount < 0) {
+        float_raise(float_flag_invalid STATUS_VAR);
+        return (int64_t)LIT64(0xFFFFFFFFFFFFFFFF);
+    }
+
+    aSig64 = aSig;
+    aSig64 <<= 40;
+    shift64ExtraRightJamming(aSig64, 0, shiftCount, &aSig64, &aSigExtra);
+    return roundAndPackUint64(aSign, aSig64, aSigExtra STATUS_VAR);
+}
+
+/*----------------------------------------------------------------------------
+| Returns the result of converting the single-precision floating-point value
 | `a' to the 64-bit two's complement integer format.  The conversion is
 | performed according to the IEC/IEEE Standard for Binary Floating-Point
 | Arithmetic, except that the conversion is always rounded toward zero.  If
diff --git a/include/fpu/softfloat.h b/include/fpu/softfloat.h
index 3790b10b3c..c49e836424 100644
--- a/include/fpu/softfloat.h
+++ b/include/fpu/softfloat.h
@@ -291,6 +291,7 @@ int32 float32_to_int32_round_to_zero( float32 STATUS_PARAM );
 uint32 float32_to_uint32( float32 STATUS_PARAM );
 uint32 float32_to_uint32_round_to_zero( float32 STATUS_PARAM );
 int64 float32_to_int64( float32 STATUS_PARAM );
+uint64 float32_to_uint64(float32 STATUS_PARAM);
 int64 float32_to_int64_round_to_zero( float32 STATUS_PARAM );
 float64 float32_to_float64( float32 STATUS_PARAM );
 floatx80 float32_to_floatx80( float32 STATUS_PARAM );