[Qemu-devel] [RFC PATCH v0] softfloat: Add float128_to_uint64_round_to_zero()

[Bharata B Rao <bharata@linux.vnet.ibm.com>]

Implement float128_to_uint64() and use that to implement
float128_to_uint64_round_to_zero()

This is required by xscvqpudz instruction of PowerPC ISA 3.0.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
---
 fpu/softfloat.c         | 65 +++++++++++++++++++++++++++++++++++++++++++++++++
 include/fpu/softfloat.h |  2 ++
 2 files changed, 67 insertions(+)

diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index c295f31..49a06c5 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -6110,6 +6110,71 @@ int64_t float128_to_int64_round_to_zero(float128 a, float_status *status)
 
 /*----------------------------------------------------------------------------
 | Returns the result of converting the quadruple-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
+| positive integer is returned.  Otherwise, if the conversion overflows, the
+| largest unsigned integer is returned. If 'a' is negative, the value is
+| rounded and zero is returned; negative values that do not round to zero
+| will raise the inexact exception.
+*----------------------------------------------------------------------------*/
+
+uint64_t float128_to_uint64(float128 a, float_status *status)
+{
+    flag aSign;
+    int32_t aExp, shiftCount;
+    uint64_t aSig0, aSig1;
+
+    aSig1 = extractFloat128Frac1( a );
+    aSig0 = extractFloat128Frac0( a );
+    aExp = extractFloat128Exp( a );
+    aSign = extractFloat128Sign( a );
+    if ( aExp ) aSig0 |= LIT64( 0x0001000000000000 );
+    shiftCount = 0x402F - aExp;
+    if ( shiftCount <= 0 ) {
+        if ( 0x403E < aExp ) {
+            float_raise(float_flag_invalid, status);
+            if (    ! aSign
+                 || (    ( aExp == 0x7FFF )
+                      && ( aSig1 || ( aSig0 != LIT64( 0x0001000000000000 ) ) )
+                    )
+               ) {
+                return LIT64( 0xFFFFFFFFFFFFFFFF );
+            }
+            return 0;
+        }
+        shortShift128Left( aSig0, aSig1, - shiftCount, &aSig0, &aSig1 );
+    }
+    else {
+        shift64ExtraRightJamming( aSig0, aSig1, shiftCount, &aSig0, &aSig1 );
+    }
+    return roundAndPackUint64(aSign, aSig0, aSig1, status);
+}
+
+/*----------------------------------------------------------------------------
+| Returns the result of converting the quadruple-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.
+| according to the current rounding mode.  If `a' is a NaN, the largest
+| positive integer is returned.  Otherwise, if the conversion overflows, the
+| largest unsigned integer is returned. If 'a' is negative, the value is
+| rounded and zero is returned; negative values that do not round to zero
+| will raise the inexact exception.
+*----------------------------------------------------------------------------*/
+
+uint64_t float128_to_uint64_round_to_zero(float128 a, float_status *status)
+{
+    signed char current_rounding_mode = status->float_rounding_mode;
+    set_float_rounding_mode(float_round_to_zero, status);
+    uint64_t v = float128_to_uint64(a, status);
+    set_float_rounding_mode(current_rounding_mode, status);
+    return v;
+}
+
+/*----------------------------------------------------------------------------
+| Returns the result of converting the quadruple-precision floating-point
 | value `a' to the single-precision floating-point format.  The conversion
 | is performed according to the IEC/IEEE Standard for Binary Floating-Point
 | Arithmetic.
diff --git a/include/fpu/softfloat.h b/include/fpu/softfloat.h
index 842ec6b..4e99253 100644
--- a/include/fpu/softfloat.h
+++ b/include/fpu/softfloat.h
@@ -712,6 +712,8 @@ int32_t float128_to_int32(float128, float_status *status);
 int32_t float128_to_int32_round_to_zero(float128, float_status *status);
 int64_t float128_to_int64(float128, float_status *status);
 int64_t float128_to_int64_round_to_zero(float128, float_status *status);
+uint64_t float128_to_uint64(float128, float_status *status);
+uint64_t float128_to_uint64_round_to_zero(float128, float_status *status);
 float32 float128_to_float32(float128, float_status *status);
 float64 float128_to_float64(float128, float_status *status);
 floatx80 float128_to_floatx80(float128, float_status *status);
-- 
2.7.4