fpu/softfloat: Refactor floatx80 format NaN classification to share code

The floatx80_is_[quiet|signaling]_nan functions contain duplicated
logic that should be shared.
This commit introduces floatx80_nan_is_snan helper function that
determine if a NaN is signaling and change the return type of
floatx80_is_[signaling|quiet]_nan to bool.

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Max Chou <max.chou@sifive.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Chao Liu <chao.liu.zevorn@gmail.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20260204051756.667397-4-max.chou@sifive.com>

diff --git a/fpu/softfloat-specialize.c.inc b/fpu/softfloat-specialize.c.inc
index 7d2515c1fae2a161a4549e6db793b5f59c9e194c..9ed968c79b150a49130e3d258ce6fd505c1e06a8 100644 (file)
--- a/fpu/softfloat-specialize.c.inc
+++ b/fpu/softfloat-specialize.c.inc
@@ -357,53 +357,38 @@ bool float64_is_signaling_nan(float64 a_, float_status *status)
 }
 
 /*----------------------------------------------------------------------------
-| Returns 1 if the extended double-precision floating-point value `a' is a
-| quiet NaN; otherwise returns 0. This slightly differs from the same
-| function for other types as floatx80 has an explicit bit.
+| Determine if a floatx80 NaN is signaling NaN.
+| The MSB of frac differs from the same function for other types as floatx80
+| has an explicit bit.
 *----------------------------------------------------------------------------*/
 
-int floatx80_is_quiet_nan(floatx80 a, float_status *status)
+static bool floatx80_nan_is_snan(floatx80 a, float_status *status)
 {
     if (no_signaling_nans(status)) {
-        return floatx80_is_any_nan(a);
-    } else {
-        if (snan_bit_is_one(status)) {
-            uint64_t aLow;
-
-            aLow = a.low & ~0x4000000000000000ULL;
-            return ((a.high & 0x7FFF) == 0x7FFF)
-                && (aLow << 1)
-                && (a.low == aLow);
-        } else {
-            return ((a.high & 0x7FFF) == 0x7FFF)
-                && (UINT64_C(0x8000000000000000) <= ((uint64_t)(a.low << 1)));
-        }
+        return false;
     }
+    bool frac_msb_is_one = (a.low >> 62) & 1;
+    return frac_msb_is_one == snan_bit_is_one(status);
 }
 
 /*----------------------------------------------------------------------------
 | Returns 1 if the extended double-precision floating-point value `a' is a
-| signaling NaN; otherwise returns 0. This slightly differs from the same
-| function for other types as floatx80 has an explicit bit.
+| quiet NaN; otherwise returns 0.
 *----------------------------------------------------------------------------*/
 
-int floatx80_is_signaling_nan(floatx80 a, float_status *status)
+bool floatx80_is_quiet_nan(floatx80 a, float_status *status)
 {
-    if (no_signaling_nans(status)) {
-        return 0;
-    } else {
-        if (snan_bit_is_one(status)) {
-            return ((a.high & 0x7FFF) == 0x7FFF)
-                && ((a.low << 1) >= 0x8000000000000000ULL);
-        } else {
-            uint64_t aLow;
-
-            aLow = a.low & ~UINT64_C(0x4000000000000000);
-            return ((a.high & 0x7FFF) == 0x7FFF)
-                && (uint64_t)(aLow << 1)
-                && (a.low == aLow);
-        }
-    }
+    return floatx80_is_any_nan(a) && !floatx80_nan_is_snan(a, status);
+}
+
+/*----------------------------------------------------------------------------
+| Returns 1 if the extended double-precision floating-point value `a' is a
+| signaling NaN; otherwise returns 0.
+*----------------------------------------------------------------------------*/
+
+bool floatx80_is_signaling_nan(floatx80 a, float_status *status)
+{
+    return floatx80_is_any_nan(a) && floatx80_nan_is_snan(a, status);
 }
 
 /*----------------------------------------------------------------------------

diff --git a/include/fpu/softfloat.h b/include/fpu/softfloat.h
index 66b0c47b5eb3eac0d11e8cb293a3ab97f5f97267..69b9041ef082a02155f998c93a2f0f3e6045a94b 100644 (file)
--- a/include/fpu/softfloat.h
+++ b/include/fpu/softfloat.h
@@ -978,8 +978,8 @@ floatx80 floatx80_rem(floatx80, floatx80, float_status *status);
 floatx80 floatx80_sqrt(floatx80, float_status *status);
 FloatRelation floatx80_compare(floatx80, floatx80, float_status *status);
 FloatRelation floatx80_compare_quiet(floatx80, floatx80, float_status *status);
-int floatx80_is_quiet_nan(floatx80, float_status *status);
-int floatx80_is_signaling_nan(floatx80, float_status *status);
+bool floatx80_is_quiet_nan(floatx80, float_status *status);
+bool floatx80_is_signaling_nan(floatx80, float_status *status);
 floatx80 floatx80_silence_nan(floatx80, float_status *status);
 floatx80 floatx80_scalbn(floatx80, int, float_status *status);