From 4cec31fc23b28271a2ed0b290e65699dffac3fee Mon Sep 17 00:00:00 2001
From: Szabolcs Nagy <nsz@port70.net>
Date: Mon, 2 Sep 2013 23:33:20 +0000
Subject: math: ilogb cleanup

* consistent code style
* explicit union instead of typedef for double and float bit access
* turn FENV_ACCESS ON to make 0/0.0f raise invalid flag
* (untested) ld128 version of ilogbl (used by logbl which has ld128 support)
---
 src/math/ilogbl.c | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

(limited to 'src/math/ilogbl.c')

diff --git a/src/math/ilogbl.c b/src/math/ilogbl.c
index 7df6eb6c..7b1a9cf8 100644
--- a/src/math/ilogbl.c
+++ b/src/math/ilogbl.c
@@ -9,23 +9,46 @@ int ilogbl(long double x)
 #elif LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384
 int ilogbl(long double x)
 {
+	#pragma STDC FENV_ACCESS ON
 	union ldshape u = {x};
 	uint64_t m = u.i.m;
 	int e = u.i.se & 0x7fff;
 
 	if (!e) {
 		if (m == 0) {
-			FORCE_EVAL(x/x);
+			FORCE_EVAL(0/0.0f);
 			return FP_ILOGB0;
 		}
 		/* subnormal x */
-		for (e = -0x3fff+1; m < (uint64_t)1<<63; e--, m<<=1);
+		for (e = -0x3fff+1; m>>63 == 0; e--, m<<=1);
 		return e;
 	}
 	if (e == 0x7fff) {
 		FORCE_EVAL(0/0.0f);
-		/* in ld80 msb is set in inf */
-		return m << 1 ? FP_ILOGBNAN : INT_MAX;
+		return m<<1 ? FP_ILOGBNAN : INT_MAX;
+	}
+	return e - 0x3fff;
+}
+#elif LDBL_MANT_DIG == 113 && LDBL_MAX_EXP == 16384
+int ilogbl(long double x)
+{
+	#pragma STDC FENV_ACCESS ON
+	union ldshape u = {x};
+	int e = u.i.se & 0x7fff;
+
+	if (!e) {
+		if (x == 0) {
+			FORCE_EVAL(0/0.0f);
+			return FP_ILOGB0;
+		}
+		/* subnormal x */
+		x *= 0x1p120;
+		return ilogbl(x) - 120;
+	}
+	if (e == 0x7fff) {
+		FORCE_EVAL(0/0.0f);
+		u.i.se = 0;
+		return u.f ? FP_ILOGBNAN : INT_MAX;
 	}
 	return e - 0x3fff;
 }
-- 
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