From 27767aafa21754e6cdbf52a719e7ce395f0fe672 Mon Sep 17 00:00:00 2001
From: Zoltán Vörös
Date: Sat, 15 Feb 2020 19:28:56 +0100
Subject: lib/libm_dbl: Add round.c source code.

This code is imported from musl, to match existing code in libm_dbl.

The file is also added to the build in stm32/Makefile.  It's not needed by
the core code but, similar to c5cc64175be32cb1e4f3f1a249667bc9f5a12613,
allows round() to be used by user C modules or board extensions.
---
 lib/libm_dbl/round.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)
 create mode 100644 lib/libm_dbl/round.c

(limited to 'lib')

diff --git a/lib/libm_dbl/round.c b/lib/libm_dbl/round.c
new file mode 100644
index 000000000..130d58d25
--- /dev/null
+++ b/lib/libm_dbl/round.c
@@ -0,0 +1,35 @@
+#include "libm.h"
+
+#if FLT_EVAL_METHOD==0 || FLT_EVAL_METHOD==1
+#define EPS DBL_EPSILON
+#elif FLT_EVAL_METHOD==2
+#define EPS LDBL_EPSILON
+#endif
+static const double_t toint = 1/EPS;
+
+double round(double x)
+{
+	union {double f; uint64_t i;} u = {x};
+	int e = u.i >> 52 & 0x7ff;
+	double_t y;
+
+	if (e >= 0x3ff+52)
+		return x;
+	if (u.i >> 63)
+		x = -x;
+	if (e < 0x3ff-1) {
+		/* raise inexact if x!=0 */
+		FORCE_EVAL(x + toint);
+		return 0*u.f;
+	}
+	y = x + toint - toint - x;
+	if (y > 0.5)
+		y = y + x - 1;
+	else if (y <= -0.5)
+		y = y + x + 1;
+	else
+		y = y + x;
+	if (u.i >> 63)
+		y = -y;
+	return y;
+}
-- 
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