1 files changed, 83 insertions, 0 deletions
diff --git a/libc-top-half/musl/src/math/sqrtf.c b/libc-top-half/musl/src/math/sqrtf.c
new file mode 100644
index 0000000..740d81c
--- /dev/null
+++ b/libc-top-half/musl/src/math/sqrtf.c
@@ -0,0 +1,83 @@
+#include <stdint.h>
+#include <math.h>
+#include "libm.h"
+#include "sqrt_data.h"
+
+#define FENV_SUPPORT 1
+
+static inline uint32_t mul32(uint32_t a, uint32_t b)
+{
+	return (uint64_t)a*b >> 32;
+}
+
+/* see sqrt.c for more detailed comments.  */
+
+float sqrtf(float x)
+{
+	uint32_t ix, m, m1, m0, even, ey;
+
+	ix = asuint(x);
+	if (predict_false(ix - 0x00800000 >= 0x7f800000 - 0x00800000)) {
+		/* x < 0x1p-126 or inf or nan.  */
+		if (ix * 2 == 0)
+			return x;
+		if (ix == 0x7f800000)
+			return x;
+		if (ix > 0x7f800000)
+			return __math_invalidf(x);
+		/* x is subnormal, normalize it.  */
+		ix = asuint(x * 0x1p23f);
+		ix -= 23 << 23;
+	}
+
+	/* x = 4^e m; with int e and m in [1, 4).  */
+	even = ix & 0x00800000;
+	m1 = (ix << 8) | 0x80000000;
+	m0 = (ix << 7) & 0x7fffffff;
+	m = even ? m0 : m1;
+
+	/* 2^e is the exponent part of the return value.  */
+	ey = ix >> 1;
+	ey += 0x3f800000 >> 1;
+	ey &= 0x7f800000;
+
+	/* compute r ~ 1/sqrt(m), s ~ sqrt(m) with 2 goldschmidt iterations.  */
+	static const uint32_t three = 0xc0000000;
+	uint32_t r, s, d, u, i;
+	i = (ix >> 17) % 128;
+	r = (uint32_t)__rsqrt_tab[i] << 16;
+	/* |r*sqrt(m) - 1| < 0x1p-8 */
+	s = mul32(m, r);
+	/* |s/sqrt(m) - 1| < 0x1p-8 */
+	d = mul32(s, r);
+	u = three - d;
+	r = mul32(r, u) << 1;
+	/* |r*sqrt(m) - 1| < 0x1.7bp-16 */
+	s = mul32(s, u) << 1;
+	/* |s/sqrt(m) - 1| < 0x1.7bp-16 */
+	d = mul32(s, r);
+	u = three - d;
+	s = mul32(s, u);
+	/* -0x1.03p-28 < s/sqrt(m) - 1 < 0x1.fp-31 */
+	s = (s - 1)>>6;
+	/* s < sqrt(m) < s + 0x1.08p-23 */
+
+	/* compute nearest rounded result.  */
+	uint32_t d0, d1, d2;
+	float y, t;
+	d0 = (m << 16) - s*s;
+	d1 = s - d0;
+	d2 = d1 + s + 1;
+	s += d1 >> 31;
+	s &= 0x007fffff;
+	s |= ey;
+	y = asfloat(s);
+	if (FENV_SUPPORT) {
+		/* handle rounding and inexact exception. */
+		uint32_t tiny = predict_false(d2==0) ? 0 : 0x01000000;
+		tiny |= (d1^d2) & 0x80000000;
+		t = asfloat(tiny);
+		y = eval_as_float(y + t);
+	}
+	return y;
+}