Sync libm with upstream FreeBSD.

Upstream SHA 78599c32efed3247d165302a1fbe8d9203e38974.

Test: treehugger
Change-Id: Ib103d211315e320df89a6f0bcb30cd8ba67dd603
diff --git a/libm/upstream-freebsd/lib/msun/src/k_exp.c b/libm/upstream-freebsd/lib/msun/src/k_exp.c
index 7cc083f..dd15ff4 100644
--- a/libm/upstream-freebsd/lib/msun/src/k_exp.c
+++ b/libm/upstream-freebsd/lib/msun/src/k_exp.c
@@ -27,7 +27,7 @@
  */
 
 #include <sys/cdefs.h>
-__FBSDID("$FreeBSD: head/lib/msun/src/k_exp.c 326219 2017-11-26 02:00:33Z pfg $");
+__FBSDID("$FreeBSD$");
 
 #include <complex.h>
 
@@ -88,7 +88,7 @@
 double complex
 __ldexp_cexp(double complex z, int expt)
 {
-	double x, y, exp_x, scale1, scale2;
+	double c, exp_x, s, scale1, scale2, x, y;
 	int ex_expt, half_expt;
 
 	x = creal(z);
@@ -105,6 +105,7 @@
 	half_expt = expt - half_expt;
 	INSERT_WORDS(scale2, (0x3ff + half_expt) << 20, 0);
 
-	return (CMPLX(cos(y) * exp_x * scale1 * scale2,
-	    sin(y) * exp_x * scale1 * scale2));
+	sincos(y, &s, &c);
+	return (CMPLX(c * exp_x * scale1 * scale2,
+	    s * exp_x * scale1 * scale2));
 }