softfloat: Introduce float32_to_uint64_round_to_zero

This change adds the float32_to_uint64_round_to_zero function to the softfloat
library.  This function fills out the complement of float32 to INT round-to-zero
conversion rountines, where INT is {int32_t, uint32_t, int64_t, uint64_t}.

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

Signed-off-by: Tom Musta <tommusta@gmail.com>
Tested-by: Tom Musta <tommusta@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

fpu/softfloat.c

@@ -1626,6 +1626,26 @@ uint64 float32_to_uint64(float32 a STATUS_PARAM)
     return roundAndPackUint64(aSign, aSig64, aSigExtra STATUS_VAR);
 }
 
+/*----------------------------------------------------------------------------
+| 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, except that the conversion is always rounded toward zero.  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, the result is rounded and zero is returned; values that do
+| not round to zero will raise the inexact flag.
+*----------------------------------------------------------------------------*/
+
+uint64 float32_to_uint64_round_to_zero(float32 a STATUS_PARAM)
+{
+    signed char current_rounding_mode = STATUS(float_rounding_mode);
+    set_float_rounding_mode(float_round_to_zero STATUS_VAR);
+    int64_t v = float32_to_uint64(a STATUS_VAR);
+    set_float_rounding_mode(current_rounding_mode STATUS_VAR);
+    return v;
+}
+
 /*----------------------------------------------------------------------------
 | Returns the result of converting the single-precision floating-point value
 | `a' to the 64-bit two's complement integer format.  The conversion is

include/fpu/softfloat.h

@@ -342,6 +342,7 @@ 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);
+uint64 float32_to_uint64_round_to_zero(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 );