X-Git-Url: http://nsz.repo.hu/git/?a=blobdiff_plain;f=src%2Fmath%2Fscalbn.c;h=182f561068fda7bc8321dfc7991df8b6d58e1b56;hb=716745e00e304a650a8eef57c15fbd326168096e;hp=42a2b2943e32bc9a0700f4d789bfda84d41547d0;hpb=666271c105e4137bdfa195e217799d74143370d4;p=musl

diff --git a/src/math/scalbn.c b/src/math/scalbn.c
index 42a2b294..182f5610 100644
--- a/src/math/scalbn.c
+++ b/src/math/scalbn.c
@@ -1,35 +1,33 @@
-#include "libm.h"
+#include <math.h>
+#include <stdint.h>
 
 double scalbn(double x, int n)
 {
-	/* make sure result is stored as double on overflow or underflow */
-	volatile double z;
-	double scale;
+	union {double f; uint64_t i;} u;
+	double_t y = x;
 
 	if (n > 1023) {
-		x *= 0x1p1023;
+		y *= 0x1p1023;
 		n -= 1023;
 		if (n > 1023) {
-			x *= 0x1p1023;
+			y *= 0x1p1023;
 			n -= 1023;
-			if (n > 1023) {
-				z = x * 0x1p1023;
-				return z;
-			}
+			if (n > 1023)
+				n = 1023;
 		}
 	} else if (n < -1022) {
-		x *= 0x1p-1022;
-		n += 1022;
+		/* make sure final n < -53 to avoid double
+		   rounding in the subnormal range */
+		y *= 0x1p-1022 * 0x1p53;
+		n += 1022 - 53;
 		if (n < -1022) {
-			x *= 0x1p-1022;
-			n += 1022;
-			if (n < -1022) {
-				z = x * 0x1p-1022;
-				return z;
-			}
+			y *= 0x1p-1022 * 0x1p53;
+			n += 1022 - 53;
+			if (n < -1022)
+				n = -1022;
 		}
 	}
-	INSERT_WORDS(scale, (uint32_t)(0x3ff+n)<<20, 0);
-	z = x * scale;
-	return z;
+	u.i = (uint64_t)(0x3ff+n)<<52;
+	x = y * u.f;
+	return x;
 }