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[PATCH v2] fpu/softfloat: set invalid excp flag for RISC-V muladd instru

From: frank . chang
Subject: [PATCH v2] fpu/softfloat: set invalid excp flag for RISC-V muladd instructions
Date: Tue, 20 Apr 2021 09:31:48 +0800

From: Frank Chang <frank.chang@sifive.com>

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>
 fpu/softfloat-specialize.c.inc | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fpu/softfloat-specialize.c.inc b/fpu/softfloat-specialize.c.inc
index c2f87addb25..12f29fbfc5e 100644
--- a/fpu/softfloat-specialize.c.inc
+++ b/fpu/softfloat-specialize.c.inc
@@ -624,6 +624,12 @@ 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; /* deafult NaN */
 #elif defined(TARGET_XTENSA)
      * For Xtensa, the (inf,zero,nan) case sets InvalidOp and returns

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