libm: sync with upstream.
There's potential here to maybe lose some/all of builtins.cpp, but I'll
look at that separately later.
Test: treehugger
Change-Id: I2c2bc1d0753affdd214daeb09fa1ac7cd73db347
diff --git a/libm/upstream-freebsd/lib/msun/src/s_scalbn.c b/libm/upstream-freebsd/lib/msun/src/s_scalbn.c
index b048b05..2d4f7a3 100644
--- a/libm/upstream-freebsd/lib/msun/src/s_scalbn.c
+++ b/libm/upstream-freebsd/lib/msun/src/s_scalbn.c
@@ -1,66 +1,47 @@
-/* @(#)s_scalbn.c 5.1 93/09/24 */
/*
- * ====================================================
- * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ * Copyright (c) 2005-2020 Rich Felker, et al.
*
- * Developed at SunPro, a Sun Microsystems, Inc. business.
- * Permission to use, copy, modify, and distribute this
- * software is freely granted, provided that this notice
- * is preserved.
- * ====================================================
+ * SPDX-License-Identifier: MIT
+ *
+ * Please see https://git.musl-libc.org/cgit/musl/tree/COPYRIGHT
+ * for all contributors to musl.
*/
-
-#include <sys/cdefs.h>
-__FBSDID("$FreeBSD$");
-
-/*
- * scalbn (double x, int n)
- * scalbn(x,n) returns x* 2**n computed by exponent
- * manipulation rather than by actually performing an
- * exponentiation or a multiplication.
- */
-
#include <float.h>
+#include <math.h>
+#include <stdint.h>
-#include "math.h"
-#include "math_private.h"
-
-static const double
-two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
-twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
-huge = 1.0e+300,
-tiny = 1.0e-300;
-
-double
-scalbn (double x, int n)
+double scalbn(double x, int n)
{
- int32_t k,hx,lx;
- EXTRACT_WORDS(hx,lx,x);
- k = (hx&0x7ff00000)>>20; /* extract exponent */
- if (k==0) { /* 0 or subnormal x */
- if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */
- x *= two54;
- GET_HIGH_WORD(hx,x);
- k = ((hx&0x7ff00000)>>20) - 54;
- if (n< -50000) return tiny*x; /*underflow*/
- }
- if (k==0x7ff) return x+x; /* NaN or Inf */
- k = k+n;
- if (k > 0x7fe) return huge*copysign(huge,x); /* overflow */
- if (k > 0) /* normal result */
- {SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20)); return x;}
- if (k <= -54) {
- if (n > 50000) /* in case integer overflow in n+k */
- return huge*copysign(huge,x); /*overflow*/
- else
- return tiny*copysign(tiny,x); /*underflow*/
+ union {double f; uint64_t i;} u;
+ double_t y = x;
+
+ if (n > 1023) {
+ y *= 0x1p1023;
+ n -= 1023;
+ if (n > 1023) {
+ y *= 0x1p1023;
+ n -= 1023;
+ if (n > 1023)
+ n = 1023;
+ }
+ } else if (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) {
+ y *= 0x1p-1022 * 0x1p53;
+ n += 1022 - 53;
+ if (n < -1022)
+ n = -1022;
+ }
}
- k += 54; /* subnormal result */
- SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20));
- return x*twom54;
+ u.i = (uint64_t)(0x3ff+n)<<52;
+ x = y * u.f;
+ return x;
}
-#if (LDBL_MANT_DIG == 53)
+#if (LDBL_MANT_DIG == 53) && !defined(scalbn)
__weak_reference(scalbn, ldexpl);
__weak_reference(scalbn, scalbnl);
#endif