From f839bac29c5d8167fb7a25138583006684bf9751 Mon Sep 17 00:00:00 2001
From: Bruce Evans <bde@FreeBSD.org>
Date: Fri, 22 Feb 2008 11:59:05 +0000
Subject: [PATCH] Optimize the conversion to bits a little (by about 11 cycles
 or 16% on i386 (A64), 5 cycles on amd64 (A64), and 3 cycles on ia64).  gcc
 tends to generate very bad code for accessing floating point values as bits
 except when the integer accesses have the same width as the floating point
 values, and direct accesses to bit-fields (as is common only for long double
 precision) always gives such accesses.  Use the expsign access method, which
 is good for 80-bit long doubles and hopefully no worse for 128-bit long
 doubles.  Now the generated code is less bad.  There is still unnecessary
 copying of the arg on amd64 and i386 and mysterious extra slowness on amd64.

---
 lib/msun/src/s_rintl.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/lib/msun/src/s_rintl.c b/lib/msun/src/s_rintl.c
index 7f3b444e20bc..b43df89f53f3 100644
--- a/lib/msun/src/s_rintl.c
+++ b/lib/msun/src/s_rintl.c
@@ -32,6 +32,11 @@ __FBSDID("$FreeBSD$");
 
 #include "fpmath.h"
 
+#if LDBL_MAX_EXP != 0x4000
+/* We also require the usual bias, min exp and expsign packing. */
+#error "Unsupported long double format"
+#endif
+
 #define	BIAS	(LDBL_MAX_EXP - 1)
 
 static const float
@@ -50,16 +55,19 @@ long double
 rintl(long double x)
 {
 	union IEEEl2bits u;
-	short sign;
+	uint32_t expsign;
+	int ex, sign;
 
 	u.e = x;
+	expsign = u.xbits.expsign;
+	ex = expsign & 0x7fff;
 
-	if (u.bits.exp >= BIAS + LDBL_MANT_DIG - 1) {
-		if (u.bits.exp == BIAS + LDBL_MAX_EXP)
+	if (ex >= BIAS + LDBL_MANT_DIG - 1) {
+		if (ex == BIAS + LDBL_MAX_EXP)
 			return (x + x);	/* Inf, NaN, or unsupported format */
 		return (x);		/* finite and already an integer */
 	}
-	sign = u.bits.sign;
+	sign = expsign >> 15;
 
 	/*
 	 * The following code assumes that intermediate results are
@@ -75,7 +83,7 @@ rintl(long double x)
 	 * If the result is +-0, then it must have the same sign as x, but
 	 * the above calculation doesn't always give this.  Fix up the sign.
 	 */
-	if (u.bits.exp < BIAS && x == 0.0L)
+	if (ex < BIAS && x == 0.0L)
 		return (zero[sign]);
 
 	return (x);