auto import from //depot/cupcake/@135843
diff --git a/libm/amd64/fenv.h b/libm/amd64/fenv.h
new file mode 100644
index 0000000..c4f9432
--- /dev/null
+++ b/libm/amd64/fenv.h
@@ -0,0 +1,203 @@
+/*-
+ * Copyright (c) 2004-2005 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.
+ *
+ * $FreeBSD: src/lib/msun/amd64/fenv.h,v 1.5 2005/03/16 22:34:14 das Exp $
+ */
+
+#ifndef _FENV_H_
+#define _FENV_H_
+
+#include <sys/cdefs.h>
+#include <sys/_types.h>
+
+typedef struct {
+ struct {
+ __uint32_t __control;
+ __uint32_t __status;
+ __uint32_t __tag;
+ char __other[16];
+ } __x87;
+ __uint32_t __mxcsr;
+} fenv_t;
+
+typedef __uint16_t fexcept_t;
+
+/* Exception flags */
+#define FE_INVALID 0x01
+#define FE_DENORMAL 0x02
+#define FE_DIVBYZERO 0x04
+#define FE_OVERFLOW 0x08
+#define FE_UNDERFLOW 0x10
+#define FE_INEXACT 0x20
+#define FE_ALL_EXCEPT (FE_DIVBYZERO | FE_DENORMAL | FE_INEXACT | \
+ FE_INVALID | FE_OVERFLOW | FE_UNDERFLOW)
+
+/* Rounding modes */
+#define FE_TONEAREST 0x0000
+#define FE_DOWNWARD 0x0400
+#define FE_UPWARD 0x0800
+#define FE_TOWARDZERO 0x0c00
+#define _ROUND_MASK (FE_TONEAREST | FE_DOWNWARD | \
+ FE_UPWARD | FE_TOWARDZERO)
+
+/*
+ * As compared to the x87 control word, the SSE unit's control word
+ * has the rounding control bits offset by 3 and the exception mask
+ * bits offset by 7.
+ */
+#define _SSE_ROUND_SHIFT 3
+#define _SSE_EMASK_SHIFT 7
+
+__BEGIN_DECLS
+
+/* Default floating-point environment */
+extern const fenv_t __fe_dfl_env;
+#define FE_DFL_ENV (&__fe_dfl_env)
+
+#define __fldcw(__cw) __asm __volatile("fldcw %0" : : "m" (__cw))
+#define __fldenv(__env) __asm __volatile("fldenv %0" : : "m" (__env))
+#define __fnclex() __asm __volatile("fnclex")
+#define __fnstenv(__env) __asm __volatile("fnstenv %0" : "=m" (*(__env)))
+#define __fnstcw(__cw) __asm __volatile("fnstcw %0" : "=m" (*(__cw)))
+#define __fnstsw(__sw) __asm __volatile("fnstsw %0" : "=am" (*(__sw)))
+#define __fwait() __asm __volatile("fwait")
+#define __ldmxcsr(__csr) __asm __volatile("ldmxcsr %0" : : "m" (__csr))
+#define __stmxcsr(__csr) __asm __volatile("stmxcsr %0" : "=m" (*(__csr)))
+
+static __inline int
+feclearexcept(int __excepts)
+{
+ fenv_t __env;
+
+ if (__excepts == FE_ALL_EXCEPT) {
+ __fnclex();
+ } else {
+ __fnstenv(&__env.__x87);
+ __env.__x87.__status &= ~__excepts;
+ __fldenv(__env.__x87);
+ }
+ __stmxcsr(&__env.__mxcsr);
+ __env.__mxcsr &= ~__excepts;
+ __ldmxcsr(__env.__mxcsr);
+ return (0);
+}
+
+static __inline int
+fegetexceptflag(fexcept_t *__flagp, int __excepts)
+{
+ int __mxcsr, __status;
+
+ __stmxcsr(&__mxcsr);
+ __fnstsw(&__status);
+ *__flagp = (__mxcsr | __status) & __excepts;
+ return (0);
+}
+
+int fesetexceptflag(const fexcept_t *__flagp, int __excepts);
+int feraiseexcept(int __excepts);
+
+static __inline int
+fetestexcept(int __excepts)
+{
+ int __mxcsr, __status;
+
+ __stmxcsr(&__mxcsr);
+ __fnstsw(&__status);
+ return ((__status | __mxcsr) & __excepts);
+}
+
+static __inline int
+fegetround(void)
+{
+ int __control;
+
+ /*
+ * We assume that the x87 and the SSE unit agree on the
+ * rounding mode. Reading the control word on the x87 turns
+ * out to be about 5 times faster than reading it on the SSE
+ * unit on an Opteron 244.
+ */
+ __fnstcw(&__control);
+ return (__control & _ROUND_MASK);
+}
+
+static __inline int
+fesetround(int __round)
+{
+ int __mxcsr, __control;
+
+ if (__round & ~_ROUND_MASK)
+ return (-1);
+
+ __fnstcw(&__control);
+ __control &= ~_ROUND_MASK;
+ __control |= __round;
+ __fldcw(__control);
+
+ __stmxcsr(&__mxcsr);
+ __mxcsr &= ~(_ROUND_MASK << _SSE_ROUND_SHIFT);
+ __mxcsr |= __round << _SSE_ROUND_SHIFT;
+ __ldmxcsr(__mxcsr);
+
+ return (0);
+}
+
+int fegetenv(fenv_t *__envp);
+int feholdexcept(fenv_t *__envp);
+
+static __inline int
+fesetenv(const fenv_t *__envp)
+{
+
+ __fldenv(__envp->__x87);
+ __ldmxcsr(__envp->__mxcsr);
+ return (0);
+}
+
+int feupdateenv(const fenv_t *__envp);
+
+#if __BSD_VISIBLE
+
+int feenableexcept(int __mask);
+int fedisableexcept(int __mask);
+
+static __inline int
+fegetexcept(void)
+{
+ int __control;
+
+ /*
+ * We assume that the masks for the x87 and the SSE unit are
+ * the same.
+ */
+ __fnstcw(&__control);
+ return (~__control & FE_ALL_EXCEPT);
+}
+
+#endif /* __BSD_VISIBLE */
+
+__END_DECLS
+
+#endif /* !_FENV_H_ */