fp-bit.c (unpack_d, pack_d): Properly preserve and restore a NaN's payload.

libgcc/
	* fp-bit.c (unpack_d, pack_d): Properly preserve and restore a
	NaN's payload.

From-SVN: r198622

libgcc/ChangeLog

 2013-05-06  Thomas Schwinge  <thomas@codesourcery.com>
 
+	* fp-bit.c (unpack_d, pack_d): Properly preserve and restore a
+	NaN's payload.
+
 	* fp-bit.h [FLOAT] (QUIET_NAN): Correct value.
 
 2013-04-25  Alan Modra  <amodra@gmail.com>

libgcc/fp-bit.c

@@ -213,11 +213,18 @@ pack_d (const fp_number_type *src)
   else if (isnan (src))
     {
       exp = EXPMAX;
+      /* Restore the NaN's payload.  */
+      fraction >>= NGARDS;
+      fraction &= QUIET_NAN - 1;
       if (src->class == CLASS_QNAN || 1)
 	{
 #ifdef QUIET_NAN_NEGATED
-	  fraction |= QUIET_NAN - 1;
+	  /* The quiet/signaling bit remains unset.  */
+	  /* Make sure the fraction has a non-zero value.  */
+	  if (fraction == 0)
+	    fraction |= QUIET_NAN - 1;
 #else
+	  /* Set the quiet/signaling bit.  */
 	  fraction |= QUIET_NAN;
 #endif
 	}
@@ -573,8 +580,10 @@ unpack_d (FLO_union_type * src, fp_number_type * dst)
 	    {
 	      dst->class = CLASS_SNAN;
 	    }
-	  /* Keep the fraction part as the nan number */
-	  dst->fraction.ll = fraction;
+	  /* Now that we know which kind of NaN we got, discard the
+	     quiet/signaling bit, but do preserve the NaN payload.  */
+	  fraction &= ~QUIET_NAN;
+	  dst->fraction.ll = fraction << NGARDS;
 	}
     }
   else

libgcc/fp-bit.h

@@ -297,7 +297,7 @@ typedef unsigned int UTItype __attribute__ ((mode (TI)));
 /* numeric parameters */
 /* F_D_BITOFF is the number of bits offset between the MSB of the mantissa
    of a float and of a double. Assumes there are only two float types.
-   (double::FRAC_BITS+double::NGARDS-(float::FRAC_BITS-float::NGARDS))
+   (double::FRAC_BITS+double::NGARDS-(float::FRAC_BITS+float::NGARDS))
  */
 #define F_D_BITOFF (52+8-(23+7))