fpu/softfloat: set invalid excp flag for RISC-V muladd instructions

In IEEE 754-2008 spec:
  Invalid operation exception is signaled when doing:
  fusedMultiplyAdd(0, Inf, c) or fusedMultiplyAdd(Inf, 0, c)
  unless c is a quiet NaN; if c is a quiet NaN then it is
  implementation defined whether the invalid operation exception
  is signaled.

In RISC-V Unprivileged ISA spec:
  The fused multiply-add instructions must set the invalid
  operation exception flag when the multiplicands are Inf and
  zero, even when the addend is a quiet NaN.

This commit set invalid operation execption flag for RISC-V when
multiplicands of muladd instructions are Inf and zero.

Signed-off-by: Frank Chang <frank.chang@sifive.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210420013150.21992-1-frank.chang@sifive.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/fpu/softfloat-specialize.c.inc b/fpu/softfloat-specialize.c.inc
index 9ea318f..78f699d 100644
--- a/fpu/softfloat-specialize.c.inc
+++ b/fpu/softfloat-specialize.c.inc
@@ -627,6 +627,12 @@ static int pickNaNMulAdd(FloatClass a_cls, FloatClass b_cls, FloatClass c_cls,
     } else {
         return 1;
     }
+#elif defined(TARGET_RISCV)
+    /* For RISC-V, InvalidOp is set when multiplicands are Inf and zero */
+    if (infzero) {
+        float_raise(float_flag_invalid, status);
+    }
+    return 3; /* default NaN */
 #elif defined(TARGET_XTENSA)
     /*
      * For Xtensa, the (inf,zero,nan) case sets InvalidOp and returns