softfloat: Implement fused multiply-add

Implement fused multiply-add as a softfloat primitive. This implements
"a+b*c" as a single step without any intermediate rounding; it is
specified in IEEE 754-2008 and implemented in a number of CPUs.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/fpu/softfloat.h b/fpu/softfloat.h
index 618ddee569..07c2929613 100644
--- a/fpu/softfloat.h
+++ b/fpu/softfloat.h
@@ -212,6 +212,18 @@ void set_floatx80_rounding_precision(int val STATUS_PARAM);
 void float_raise( int8 flags STATUS_PARAM);
 
 /*----------------------------------------------------------------------------
+| Options to indicate which negations to perform in float*_muladd()
+| Using these differs from negating an input or output before calling
+| the muladd function in that this means that a NaN doesn't have its
+| sign bit inverted before it is propagated.
+*----------------------------------------------------------------------------*/
+enum {
+    float_muladd_negate_c = 1,
+    float_muladd_negate_product = 2,
+    float_muladd_negate_result = 3,
+};
+
+/*----------------------------------------------------------------------------
 | Software IEC/IEEE integer-to-floating-point conversion routines.
 *----------------------------------------------------------------------------*/
 float32 int32_to_float32( int32 STATUS_PARAM );
@@ -269,6 +281,7 @@ float32 float32_sub( float32, float32 STATUS_PARAM );
 float32 float32_mul( float32, float32 STATUS_PARAM );
 float32 float32_div( float32, float32 STATUS_PARAM );
 float32 float32_rem( float32, float32 STATUS_PARAM );
+float32 float32_muladd(float32, float32, float32, int STATUS_PARAM);
 float32 float32_sqrt( float32 STATUS_PARAM );
 float32 float32_exp2( float32 STATUS_PARAM );
 float32 float32_log2( float32 STATUS_PARAM );
@@ -375,6 +388,7 @@ float64 float64_sub( float64, float64 STATUS_PARAM );
 float64 float64_mul( float64, float64 STATUS_PARAM );
 float64 float64_div( float64, float64 STATUS_PARAM );
 float64 float64_rem( float64, float64 STATUS_PARAM );
+float64 float64_muladd(float64, float64, float64, int STATUS_PARAM);
 float64 float64_sqrt( float64 STATUS_PARAM );
 float64 float64_log2( float64 STATUS_PARAM );
 int float64_eq( float64, float64 STATUS_PARAM );