libm: fix testuite failure in modf

This error is gone:
Failure: Test: modf (NaN, &x) == NaN
Result:
 is:         -0.00000000000000000000e+00  -0
 should be:   nan   nan

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

libm/float_wrappers.c

@@ -293,10 +293,9 @@ long_WRAPPER1(lround)
 float modff (float x, float *iptr)
 {
 	double y, result;
-	result = modf ( x, &y );
+	result = modf( x, &y );
 	*iptr = (float)y;
 	return (float) result;
-
 }
 #endif
 

libm/s_modf.c

@@ -37,10 +37,8 @@ double modf(double x, double *iptr)
 	    } else {
 		i = (0x000fffff)>>j0;
 		if(((i0&i)|i1)==0) {		/* x is integral */
-		    u_int32_t high;
 		    *iptr = x;
-		    GET_HIGH_WORD(high,x);
-		    INSERT_WORDS(x,high&0x80000000,0);	/* return +-0 */
+		    INSERT_WORDS(x,i0&0x80000000,0);	/* return +-0 */
 		    return x;
 		} else {
 		    INSERT_WORDS(*iptr,i0&(~i),0);
@@ -48,18 +46,17 @@ double modf(double x, double *iptr)
 		}
 	    }
 	} else if (j0>51) {		/* no fraction part */
-	    u_int32_t high;
 	    *iptr = x*one;
-	    GET_HIGH_WORD(high,x);
-	    INSERT_WORDS(x,high&0x80000000,0);	/* return +-0 */
+	    /* We must handle NaNs separately.  */
+	    if (j0 == 0x400 && ((i0 & 0xfffff) | i1))
+	      return x*one;
+	    INSERT_WORDS(x,i0&0x80000000,0);	/* return +-0 */
 	    return x;
 	} else {			/* fraction part in low x */
 	    i = ((u_int32_t)(0xffffffff))>>(j0-20);
 	    if((i1&i)==0) { 		/* x is integral */
-	        u_int32_t high;
 		*iptr = x;
-		GET_HIGH_WORD(high,x);
-		INSERT_WORDS(x,high&0x80000000,0);	/* return +-0 */
+		INSERT_WORDS(x,i0&0x80000000,0);	/* return +-0 */
 		return x;
 	    } else {
 	        INSERT_WORDS(*iptr,i0,i1&(~i));