From 4aa8c9453f4f0a2fe94bdf68aebfeb13f01198a5 Mon Sep 17 00:00:00 2001
From: Steve Kargl <kargl@FreeBSD.org>
Date: Mon, 3 Jun 2013 17:51:08 +0000
Subject: [PATCH] Introduce the macro LOG2_INTERVAL, which is log2(number of
 intervals). Use the macroi as a micro-optimization to convert a subtraction
 and division to a shift.

Obtained from:	bde
---
 lib/msun/ld128/s_expl.c | 3 ++-
 lib/msun/ld80/s_expl.c  | 4 +++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/lib/msun/ld128/s_expl.c b/lib/msun/ld128/s_expl.c
index 96145307e556..60e6425d9f09 100644
--- a/lib/msun/ld128/s_expl.c
+++ b/lib/msun/ld128/s_expl.c
@@ -38,6 +38,7 @@ __FBSDID("$FreeBSD$");
 #include "math_private.h"
 
 #define	INTERVALS	128
+#define	LOG2_INTERVALS	7
 #define	BIAS	(LDBL_MAX_EXP - 1)
 
 static volatile const long double tiny = 0x1p-10000L;
@@ -229,7 +230,7 @@ expl(long double x)
 	fn = x * INV_L + 0x1.8p112 - 0x1.8p112;
 	n = (int)fn;
 	n2 = (unsigned)n % INTERVALS;
-	k = (n - n2) / INTERVALS;
+	k = n >> LOG2_INTERVALS;
 	r1 = x - fn * L1;
 	r2 = -fn * L2;
 
diff --git a/lib/msun/ld80/s_expl.c b/lib/msun/ld80/s_expl.c
index 38568f23bf97..c7d923d2e61b 100644
--- a/lib/msun/ld80/s_expl.c
+++ b/lib/msun/ld80/s_expl.c
@@ -50,6 +50,7 @@ __FBSDID("$FreeBSD$");
 #include "math_private.h"
 
 #define	INTERVALS	128
+#define	LOG2_INTERVALS	7
 #define	BIAS	(LDBL_MAX_EXP - 1)
 
 static const long double
@@ -269,7 +270,8 @@ expl(long double x)
 	n = (int)fn;
 #endif
 	n2 = (unsigned)n % INTERVALS;
-	k = (n - n2) / INTERVALS;
+	/* Depend on the sign bit being propagated: */
+	k = n >> LOG2_INTERVALS;
 	r1 = x - fn * L1;
 	r2 = -fn * L2;