1 files changed, 72 insertions, 0 deletions
diff --git a/libc-top-half/musl/src/math/lrint.c b/libc-top-half/musl/src/math/lrint.c
new file mode 100644
index 0000000..ddee7a0
--- /dev/null
+++ b/libc-top-half/musl/src/math/lrint.c
@@ -0,0 +1,72 @@
+#include <limits.h>
+#include <fenv.h>
+#include <math.h>
+#include "libm.h"
+
+/*
+If the result cannot be represented (overflow, nan), then
+lrint raises the invalid exception.
+
+Otherwise if the input was not an integer then the inexact
+exception is raised.
+
+C99 is a bit vague about whether inexact exception is
+allowed to be raised when invalid is raised.
+(F.9 explicitly allows spurious inexact exceptions, F.9.6.5
+does not make it clear if that rule applies to lrint, but
+IEEE 754r 7.8 seems to forbid spurious inexact exception in
+the ineger conversion functions)
+
+So we try to make sure that no spurious inexact exception is
+raised in case of an overflow.
+
+If the bit size of long > precision of double, then there
+cannot be inexact rounding in case the result overflows,
+otherwise LONG_MAX and LONG_MIN can be represented exactly
+as a double.
+*/
+
+#if LONG_MAX < 1U<<53 && defined(FE_INEXACT)
+#include <float.h>
+#include <stdint.h>
+#if FLT_EVAL_METHOD==0 || FLT_EVAL_METHOD==1
+#define EPS DBL_EPSILON
+#elif FLT_EVAL_METHOD==2
+#define EPS LDBL_EPSILON
+#endif
+#ifdef __GNUC__
+/* avoid stack frame in lrint */
+__attribute__((noinline))
+#endif
+static long lrint_slow(double x)
+{
+	#pragma STDC FENV_ACCESS ON
+	int e;
+
+	e = fetestexcept(FE_INEXACT);
+	x = rint(x);
+	if (!e && (x > LONG_MAX || x < LONG_MIN))
+		feclearexcept(FE_INEXACT);
+	/* conversion */
+	return x;
+}
+
+long lrint(double x)
+{
+	uint32_t abstop = asuint64(x)>>32 & 0x7fffffff;
+	uint64_t sign = asuint64(x) & (1ULL << 63);
+
+	if (abstop < 0x41dfffff) {
+		/* |x| < 0x7ffffc00, no overflow */
+		double_t toint = asdouble(asuint64(1/EPS) | sign);
+		double_t y = x + toint - toint;
+		return (long)y;
+	}
+	return lrint_slow(x);
+}
+#else
+long lrint(double x)
+{
+	return rint(x);
+}
+#endif