faster lrint and llrint functions

A faster workaround for spurious inexact exceptions
when the result cannot be represented. The old code
actually could be wrong, because gcc reordered the
integer conversion and the exception check.

1 files changed, 21 insertions, 7 deletions

diff --git a/src/math/llrintl.c b/src/math/llrintl.c
index ec2cf86b..f1cc47ed 100644
--- a/src/math/llrintl.c
+++ b/src/math/llrintl.c
@@ -1,5 +1,7 @@
-#include <math.h>
-#include <float.h>
+#include <limits.h>
+#include <fenv.h>
+#include "libm.h"
+
 
 #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
 long long llrintl(long double x)
@@ -7,10 +9,22 @@ long long llrintl(long double x)
 	return llrint(x);
 }
 #else
-#define type            long double
-#define roundit         rintl
-#define dtype           long long
-#define fn              llrintl
+/*
+see comments in lrint.c
 
-#include "lrint.c"
+Note that if LLONG_MAX == 0x7fffffffffffffff && LDBL_MANT_DIG == 64
+then x == 2**63 - 0.5 is the only input that overflows and
+raises inexact (with tonearest or upward rounding mode)
+*/
+long long llrintl(long double x)
+{
+	int e;
+
+	e = fetestexcept(FE_INEXACT);
+	x = rintl(x);
+	if (!e && (x > LLONG_MAX || x < LLONG_MIN))
+		feclearexcept(FE_INEXACT);
+	/* conversion */
+	return x;
+}
 #endif