Sync libm with upstream FreeBSD.

Upstream SHA 78599c32efed3247d165302a1fbe8d9203e38974.

Test: treehugger
Change-Id: Ib103d211315e320df89a6f0bcb30cd8ba67dd603
diff --git a/libm/upstream-freebsd/lib/msun/ld128/k_expl.h b/libm/upstream-freebsd/lib/msun/ld128/k_expl.h
index b80d00e..159338f 100644
--- a/libm/upstream-freebsd/lib/msun/ld128/k_expl.h
+++ b/libm/upstream-freebsd/lib/msun/ld128/k_expl.h
@@ -31,7 +31,7 @@
  */
 
 #include <sys/cdefs.h>
-__FBSDID("$FreeBSD: head/lib/msun/ld128/k_expl.h 336545 2018-07-20 12:42:24Z bde $");
+__FBSDID("$FreeBSD$");
 
 /*
  * ld128 version of k_expl.h.  See ../ld80/s_expl.c for most comments.
@@ -265,7 +265,8 @@
 /*
  * XXX: the rest of the functions are identical for ld80 and ld128.
  * However, we should use scalbnl() for ld128, since long double
- * multiplication is very slow on the only supported ld128 arch (sparc64).
+ * multiplication was very slow on sparc64 and no new evaluation has
+ * been made for aarch64 and/or riscv.
  */
 
 static inline void
@@ -299,7 +300,7 @@
 static inline long double complex
 __ldexp_cexpl(long double complex z, int expt)
 {
-	long double exp_x, hi, lo;
+	long double c, exp_x, hi, lo, s;
 	long double x, y, scale1, scale2;
 	int half_expt, k;
 
@@ -307,16 +308,17 @@
 	y = cimagl(z);
 	__k_expl(x, &hi, &lo, &k);
 
-	exp_x = (lo + hi) * 0x1p16382;
+	exp_x = (lo + hi) * 0x1p16382L;
 	expt += k - 16382;
 
 	scale1 = 1;
 	half_expt = expt / 2;
 	SET_LDBL_EXPSIGN(scale1, BIAS + half_expt);
 	scale2 = 1;
-	SET_LDBL_EXPSIGN(scale1, BIAS + expt - half_expt);
+	SET_LDBL_EXPSIGN(scale2, BIAS + expt - half_expt);
 
-	return (CMPLXL(cos(y) * exp_x * scale1 * scale2,
-	    sinl(y) * exp_x * scale1 * scale2));
+	sincosl(y, &s, &c);
+	return (CMPLXL(c * exp_x * scale1 * scale2,
+	    s * exp_x * scale1 * scale2));
 }
 #endif /* _COMPLEX_H */