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-rw-r--r--modules/fdlibm/src/s_scalbn.cpp43
1 files changed, 43 insertions, 0 deletions
diff --git a/modules/fdlibm/src/s_scalbn.cpp b/modules/fdlibm/src/s_scalbn.cpp
new file mode 100644
index 0000000000..13fa7f129d
--- /dev/null
+++ b/modules/fdlibm/src/s_scalbn.cpp
@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2005-2020 Rich Felker, et al.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Please see https://git.musl-libc.org/cgit/musl/tree/COPYRIGHT
+ * for all contributors to musl.
+ */
+#include <float.h>
+#include <stdint.h>
+
+#include "math_private.h"
+
+double scalbn(double x, int n)
+{
+ 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;
+ }
+ }
+ u.i = (uint64_t)(0x3ff+n)<<52;
+ x = y * u.f;
+ return x;
+}