Optimize ldexp and scalbn

1 files changed, 8 insertions, 16 deletions

diff --git a/sysdeps/ieee754/dbl-64/wordsize-64/s_scalbn.c b/sysdeps/ieee754/dbl-64/wordsize-64/s_scalbn.c
index 25cf3b1699..7f0e21f646 100644
--- a/sysdeps/ieee754/dbl-64/wordsize-64/s_scalbn.c
+++ b/sysdeps/ieee754/dbl-64/wordsize-64/s_scalbn.c
@@ -1,4 +1,3 @@
-/* @(#)s_scalbn.c 5.1 93/09/24 */
 /*
  * ====================================================
  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
@@ -20,39 +19,32 @@
 #include "math.h"
 #include "math_private.h"
 
-#ifdef __STDC__
 static const double
-#else
-static double
-#endif
 two54   =  1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
 twom54  =  5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
 huge   = 1.0e+300,
 tiny   = 1.0e-300;
 
-#ifdef __STDC__
-	double __scalbn (double x, int n)
-#else
-	double __scalbn (x,n)
-	double x; int n;
-#endif
+double
+__scalbn (double x, int n)
 {
 	int64_t ix;
 	int64_t k;
 	EXTRACT_WORDS64(ix,x);
 	k = (ix >> 52) & 0x7ff;			/* extract exponent */
-	if (k==0) {				/* 0 or subnormal x */
+	if (__builtin_expect(k==0, 0)) {	/* 0 or subnormal x */
 	    if ((ix & UINT64_C(0xfffffffffffff))==0) return x; /* +-0 */
 	    x *= two54;
 	    EXTRACT_WORDS64(ix,x);
 	    k = ((ix >> 52) & 0x7ff) - 54;
 	    }
-	if (k==0x7ff) return x+x;		/* NaN or Inf */
+	if (__builtin_expect(k==0x7ff, 0)) return x+x;	/* NaN or Inf */
 	k = k+n;
-	if (n> 50000 || k >  0x7fe)
+	if (__builtin_expect(n> 50000 || k >  0x7fe, 0))
 	  return huge*__copysign(huge,x); /* overflow  */
-	if (n< -50000) return tiny*__copysign(tiny,x); /*underflow*/
-	if (k > 0)				/* normal result */
+	if (__builtin_expect(n< -50000, 0))
+	  return tiny*__copysign(tiny,x); /*underflow*/
+	if (__builtin_expect(k > 0, 1))		/* normal result */
 	    {INSERT_WORDS64(x,(ix&UINT64_C(0x800fffffffffffff))|(k<<52));
 	      return x;}
 	if (k <= -54)