[02/21] softfloat: pass float_status pointer to pickNaN

Commit Message

Max Filippov July 6, 2020, 11:47 p.m. UTC

Pass float_status structure pointer to the pickNaN so that
machine-specific settings are available to NaN selection code.
Add use_first_nan property to float_status and use it in Xtensa-specific
pickNaN.

Cc: Peter Maydell <[e-mail]>
Cc: "Alex Bennée" <[e-mail]>
Signed-off-by: Max Filippov <[e-mail]>
---
 fpu/softfloat-specialize.inc.c  | 30 ++++++++++++++++++++++++------
 fpu/softfloat.c                 |  2 +-
 include/fpu/softfloat-helpers.h |  5 +++++
 include/fpu/softfloat-types.h   |  1 +
 4 files changed, 31 insertions(+), 7 deletions(-)

Comments

Alex Bennée July 7, 2020, 10:29 a.m. UTC | #1

Max Filippov <[e-mail]> writes:

> Pass float_status structure pointer to the pickNaN so that
> machine-specific settings are available to NaN selection code.
> Add use_first_nan property to float_status and use it in Xtensa-specific
> pickNaN.
>
> Cc: Peter Maydell <[e-mail]>
> Cc: "Alex Bennée" <[e-mail]>
> Signed-off-by: Max Filippov <[e-mail]>

Reviewed-by: Alex Bennée <[e-mail]>

Patch

diff --git a/fpu/softfloat-specialize.inc.c b/fpu/softfloat-specialize.inc.c
index b26bc039b0b6..e17327b405c5 100644
--- a/fpu/softfloat-specialize.inc.c
+++ b/fpu/softfloat-specialize.inc.c
@@ -368,7 +368,7 @@  static float32 commonNaNToFloat32(commonNaNT a, float_status *status)
 *----------------------------------------------------------------------------*/
 
 static int pickNaN(FloatClass a_cls, FloatClass b_cls,
-                   bool aIsLargerSignificand)
+                   bool aIsLargerSignificand, float_status *status)
 {
 #if defined(TARGET_ARM) || defined(TARGET_MIPS) || defined(TARGET_HPPA)
     /* ARM mandated NaN propagation rules (see FPProcessNaNs()), take
@@ -401,7 +401,7 @@  static int pickNaN(FloatClass a_cls, FloatClass b_cls,
     } else {
         return 1;
     }
-#elif defined(TARGET_PPC) || defined(TARGET_XTENSA) || defined(TARGET_M68K)
+#elif defined(TARGET_PPC) || defined(TARGET_M68K)
     /* PowerPC propagation rules:
      *  1. A if it sNaN or qNaN
      *  2. B if it sNaN or qNaN
@@ -426,6 +426,24 @@  static int pickNaN(FloatClass a_cls, FloatClass b_cls,
     } else {
         return 1;
     }
+#elif defined(TARGET_XTENSA)
+    /*
+     * Xtensa has two NaN propagation modes.
+     * Which one is active is controlled by float_status::use_first_nan.
+     */
+    if (status->use_first_nan) {
+        if (is_nan(a_cls)) {
+            return 0;
+        } else {
+            return 1;
+        }
+    } else {
+        if (is_nan(b_cls)) {
+            return 1;
+        } else {
+            return 0;
+        }
+    }
 #else
     /* This implements x87 NaN propagation rules:
      * SNaN + QNaN => return the QNaN
@@ -613,7 +631,7 @@  static float32 propagateFloat32NaN(float32 a, float32 b, float_status *status)
         aIsLargerSignificand = (av < bv) ? 1 : 0;
     }
 
-    if (pickNaN(a_cls, b_cls, aIsLargerSignificand)) {
+    if (pickNaN(a_cls, b_cls, aIsLargerSignificand, status)) {
         if (is_snan(b_cls)) {
             return float32_silence_nan(b, status);
         }
@@ -751,7 +769,7 @@  static float64 propagateFloat64NaN(float64 a, float64 b, float_status *status)
         aIsLargerSignificand = (av < bv) ? 1 : 0;
     }
 
-    if (pickNaN(a_cls, b_cls, aIsLargerSignificand)) {
+    if (pickNaN(a_cls, b_cls, aIsLargerSignificand, status)) {
         if (is_snan(b_cls)) {
             return float64_silence_nan(b, status);
         }
@@ -915,7 +933,7 @@  floatx80 propagateFloatx80NaN(floatx80 a, floatx80 b, float_status *status)
         aIsLargerSignificand = (a.high < b.high) ? 1 : 0;
     }
 
-    if (pickNaN(a_cls, b_cls, aIsLargerSignificand)) {
+    if (pickNaN(a_cls, b_cls, aIsLargerSignificand, status)) {
         if (is_snan(b_cls)) {
             return floatx80_silence_nan(b, status);
         }
@@ -1063,7 +1081,7 @@  static float128 propagateFloat128NaN(float128 a, float128 b,
         aIsLargerSignificand = (a.high < b.high) ? 1 : 0;
     }
 
-    if (pickNaN(a_cls, b_cls, aIsLargerSignificand)) {
+    if (pickNaN(a_cls, b_cls, aIsLargerSignificand, status)) {
         if (is_snan(b_cls)) {
             return float128_silence_nan(b, status);
         }
diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index 5e9746c2876f..a89056a1816e 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -881,7 +881,7 @@  static FloatParts pick_nan(FloatParts a, FloatParts b, float_status *s)
     } else {
         if (pickNaN(a.cls, b.cls,
                     a.frac > b.frac ||
-                    (a.frac == b.frac && a.sign < b.sign))) {
+                    (a.frac == b.frac && a.sign < b.sign), s)) {
             a = b;
         }
         if (is_snan(a.cls)) {
diff --git a/include/fpu/softfloat-helpers.h b/include/fpu/softfloat-helpers.h
index e842f83a1285..2f0674fbddec 100644
--- a/include/fpu/softfloat-helpers.h
+++ b/include/fpu/softfloat-helpers.h
@@ -95,6 +95,11 @@  static inline void set_snan_bit_is_one(bool val, float_status *status)
     status->snan_bit_is_one = val;
 }
 
+static inline void set_use_first_nan(bool val, float_status *status)
+{
+    status->use_first_nan = val;
+}
+
 static inline void set_no_signaling_nans(bool val, float_status *status)
 {
     status->no_signaling_nans = val;
diff --git a/include/fpu/softfloat-types.h b/include/fpu/softfloat-types.h
index 10bd208e559f..aaee6e4cdd23 100644
--- a/include/fpu/softfloat-types.h
+++ b/include/fpu/softfloat-types.h
@@ -167,6 +167,7 @@  typedef struct float_status {
     bool default_nan_mode;
     /* not always used -- see snan_bit_is_one() in softfloat-specialize.h */
     bool snan_bit_is_one;
+    bool use_first_nan;
     bool no_signaling_nans;
 } float_status;