From b69f695acedd4ce2798ef9ea28d834ceccc789bd Mon Sep 17 00:00:00 2001
From: Rich Felker
Date: Tue, 13 Mar 2012 01:17:53 -0400
Subject: first commit of the new libm!
thanks to the hard work of Szabolcs Nagy (nsz), identifying the best
(from correctness and license standpoint) implementations from freebsd
and openbsd and cleaning them up! musl should now fully support c99
float and long double math functions, and has near-complete complex
math support. tgmath should also work (fully on gcc-compatible
compilers, and mostly on any c99 compiler).
based largely on commit 0376d44a890fea261506f1fc63833e7a686dca19 from
nsz's libm git repo, with some additions (dummy versions of a few
missing long double complex functions, etc.) by me.
various cleanups still need to be made, including re-adding (if
they're correct) some asm functions that were dropped.
---
src/math/ilogb.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
create mode 100644 src/math/ilogb.c
(limited to 'src/math/ilogb.c')
diff --git a/src/math/ilogb.c b/src/math/ilogb.c
new file mode 100644
index 00000000..c5915a0c
--- /dev/null
+++ b/src/math/ilogb.c
@@ -0,0 +1,21 @@
+#include
+#include "libm.h"
+
+int ilogb(double x)
+{
+ union dshape u = {x};
+ int e = u.bits>>52 & 0x7ff;
+
+ if (!e) {
+ u.bits <<= 12;
+ if (u.bits == 0)
+ return FP_ILOGB0;
+ /* subnormal x */
+ // FIXME: scale up subnormals with a *0x1p53 or find top set bit with a better method
+ for (e = -0x3ff; u.bits < (uint64_t)1<<63; e--, u.bits<<=1);
+ return e;
+ }
+ if (e == 0x7ff)
+ return u.bits<<12 ? FP_ILOGBNAN : INT_MAX;
+ return e - 0x3ff;
+}
--
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