auto import from //depot/cupcake/@135843
diff --git a/libm/src/s_fmal.c b/libm/src/s_fmal.c
new file mode 100644
index 0000000..f1736fa
--- /dev/null
+++ b/libm/src/s_fmal.c
@@ -0,0 +1,182 @@
+/*-
+ * Copyright (c) 2005 David Schultz <das@FreeBSD.ORG>
+ * 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.
+ */
+
+#include <sys/cdefs.h>
+/* __FBSDID("$FreeBSD: src/lib/msun/src/s_fmal.c,v 1.2 2005/03/18 02:27:59 das Exp $"); */
+
+#include <fenv.h>
+#include <float.h>
+#include <math.h>
+
+/*
+ * Fused multiply-add: Compute x * y + z with a single rounding error.
+ *
+ * We use scaling to avoid overflow/underflow, along with the
+ * canonical precision-doubling technique adapted from:
+ *
+ * Dekker, T. A Floating-Point Technique for Extending the
+ * Available Precision. Numer. Math. 18, 224-242 (1971).
+ */
+long double
+fmal(long double x, long double y, long double z)
+{
+#if LDBL_MANT_DIG == 64
+ static const long double split = 0x1p32L + 1.0;
+#elif LDBL_MANT_DIG == 113
+ static const long double split = 0x1p57L + 1.0;
+#endif
+ long double xs, ys, zs;
+ long double c, cc, hx, hy, p, q, tx, ty;
+ long double r, rr, s;
+ int oround;
+ int ex, ey, ez;
+ int spread;
+
+ if (z == 0.0)
+ return (x * y);
+ if (x == 0.0 || y == 0.0)
+ return (x * y + z);
+
+ /* Results of frexp() are undefined for these cases. */
+ if (!isfinite(x) || !isfinite(y) || !isfinite(z))
+ return (x * y + z);
+
+ xs = frexpl(x, &ex);
+ ys = frexpl(y, &ey);
+ zs = frexpl(z, &ez);
+ oround = fegetround();
+ spread = ex + ey - ez;
+
+ /*
+ * If x * y and z are many orders of magnitude apart, the scaling
+ * will overflow, so we handle these cases specially. Rounding
+ * modes other than FE_TONEAREST are painful.
+ */
+ if (spread > LDBL_MANT_DIG * 2) {
+ fenv_t env;
+ feraiseexcept(FE_INEXACT);
+ switch(oround) {
+ case FE_TONEAREST:
+ return (x * y);
+ case FE_TOWARDZERO:
+ if (x > 0.0 ^ y < 0.0 ^ z < 0.0)
+ return (x * y);
+ feholdexcept(&env);
+ r = x * y;
+ if (!fetestexcept(FE_INEXACT))
+ r = nextafterl(r, 0);
+ feupdateenv(&env);
+ return (r);
+ case FE_DOWNWARD:
+ if (z > 0.0)
+ return (x * y);
+ feholdexcept(&env);
+ r = x * y;
+ if (!fetestexcept(FE_INEXACT))
+ r = nextafterl(r, -INFINITY);
+ feupdateenv(&env);
+ return (r);
+ default: /* FE_UPWARD */
+ if (z < 0.0)
+ return (x * y);
+ feholdexcept(&env);
+ r = x * y;
+ if (!fetestexcept(FE_INEXACT))
+ r = nextafterl(r, INFINITY);
+ feupdateenv(&env);
+ return (r);
+ }
+ }
+ if (spread < -LDBL_MANT_DIG) {
+ feraiseexcept(FE_INEXACT);
+ if (!isnormal(z))
+ feraiseexcept(FE_UNDERFLOW);
+ switch (oround) {
+ case FE_TONEAREST:
+ return (z);
+ case FE_TOWARDZERO:
+ if (x > 0.0 ^ y < 0.0 ^ z < 0.0)
+ return (z);
+ else
+ return (nextafterl(z, 0));
+ case FE_DOWNWARD:
+ if (x > 0.0 ^ y < 0.0)
+ return (z);
+ else
+ return (nextafterl(z, -INFINITY));
+ default: /* FE_UPWARD */
+ if (x > 0.0 ^ y < 0.0)
+ return (nextafterl(z, INFINITY));
+ else
+ return (z);
+ }
+ }
+
+ /*
+ * Use Dekker's algorithm to perform the multiplication and
+ * subsequent addition in twice the machine precision.
+ * Arrange so that x * y = c + cc, and x * y + z = r + rr.
+ */
+ fesetround(FE_TONEAREST);
+
+ p = xs * split;
+ hx = xs - p;
+ hx += p;
+ tx = xs - hx;
+
+ p = ys * split;
+ hy = ys - p;
+ hy += p;
+ ty = ys - hy;
+
+ p = hx * hy;
+ q = hx * ty + tx * hy;
+ c = p + q;
+ cc = p - c + q + tx * ty;
+
+ zs = ldexpl(zs, -spread);
+ r = c + zs;
+ s = r - c;
+ rr = (c - (r - s)) + (zs - s) + cc;
+
+ spread = ex + ey;
+ if (spread + ilogbl(r) > -16383) {
+ fesetround(oround);
+ r = r + rr;
+ } else {
+ /*
+ * The result is subnormal, so we round before scaling to
+ * avoid double rounding.
+ */
+ p = ldexpl(copysignl(0x1p-16382L, r), -spread);
+ c = r + p;
+ s = c - r;
+ cc = (r - (c - s)) + (p - s) + rr;
+ fesetround(oround);
+ r = (c + cc) - p;
+ }
+ return (ldexpl(r, spread));
+}