From 600e30d2b293bd19b0d0cdb7e8a517cecf482d12 Mon Sep 17 00:00:00 2001
From: Peter Maydell <peter.maydell@linaro.org>
Date: Thu, 10 Feb 2011 11:28:58 +0000
Subject: softfloat: Fix single-to-half precision float conversions

Fix various bugs in the single-to-half-precision conversion code:
 * input NaNs not correctly converted in IEEE mode
   (fixed by defining and using a commonNaNToFloat16())
 * wrong values returned when converting NaN/Inf into non-IEEE
   half precision value
 * wrong values returned for conversion of values which are
   on the boundary between denormal and zero for the half
   precision format
 * zeroes not correctly identified
 * excessively large results in non-IEEE mode should
   generate InvalidOp, not Overflow

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
---
 fpu/softfloat.c | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

(limited to 'fpu/softfloat.c')

diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index ffc8a99002..80d8cc4894 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -2796,24 +2796,30 @@ float16 float32_to_float16(float32 a, flag ieee STATUS_PARAM)
     aSign = extractFloat32Sign( a );
     if ( aExp == 0xFF ) {
         if (aSig) {
-            /* Make sure correct exceptions are raised.  */
-            float32ToCommonNaN(a STATUS_VAR);
-            aSig |= 0x00400000;
+            /* Input is a NaN */
+            float16 r = commonNaNToFloat16( float32ToCommonNaN( a STATUS_VAR ) STATUS_VAR );
+            if (!ieee) {
+                return packFloat16(aSign, 0, 0);
+            }
+            return r;
         }
-        return packFloat16(aSign, 0x1f, aSig >> 13);
+        /* Infinity */
+        if (!ieee) {
+            float_raise(float_flag_invalid STATUS_VAR);
+            return packFloat16(aSign, 0x1f, 0x3ff);
+        }
+        return packFloat16(aSign, 0x1f, 0);
     }
-    if (aExp == 0 && aSign == 0) {
+    if (aExp == 0 && aSig == 0) {
         return packFloat16(aSign, 0, 0);
     }
     /* Decimal point between bits 22 and 23.  */
     aSig |= 0x00800000;
     aExp -= 0x7f;
     if (aExp < -14) {
-        mask = 0x007fffff;
-        if (aExp < -24) {
-            aExp = -25;
-        } else {
-            mask >>= 24 + aExp;
+        mask = 0x00ffffff;
+        if (aExp >= -24) {
+            mask >>= 25 + aExp;
         }
     } else {
         mask = 0x00001fff;
@@ -2855,7 +2861,7 @@ float16 float32_to_float16(float32 a, flag ieee STATUS_PARAM)
         }
     } else {
         if (aExp > 16) {
-            float_raise( float_flag_overflow | float_flag_inexact STATUS_VAR);
+            float_raise(float_flag_invalid | float_flag_inexact STATUS_VAR);
             return packFloat16(aSign, 0x1f, 0x3ff);
         }
     }
-- 
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