ARM: Optimize IEEE-754 sqrt implementation

Use the vsqrt.f64 and vsqrt.f32 instructions if available.

1 files changed, 45 insertions, 0 deletions

diff --git a/newlib/libm/machine/arm/ef_sqrt.c b/newlib/libm/machine/arm/ef_sqrt.c
new file mode 100644
index 000000000..81c29f145
--- /dev/null
+++ b/newlib/libm/machine/arm/ef_sqrt.c
@@ -0,0 +1,45 @@
+/*-
+ * Copyright (c) 2017 embedded brains GmbH
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#if __ARM_FP & 0x4
+#include <math.h>
+
+float
+__ieee754_sqrtf(float x)
+{
+	float result;
+#if __ARM_ARCH >= 6
+	asm ("vsqrt.f32 %0, %1" : "=w" (result) : "w" (x));
+#else
+	/* VFP9 Erratum 760019, see GCC sources "gcc/config/arm/vfp.md" */
+	asm ("vsqrt.f32 %0, %1" : "=&w" (result) : "w" (x));
+#endif
+	return result;
+}
+
+#else
+#include "../../math/ef_sqrt.c"
+#endif