#
# Copyright (c) 2014 Martin Decky
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# - Redistributions of source code must retain the above copyright
#   notice, this list of conditions and the following disclaimer.
# - 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.
# - The name of the author may not be used to endorse or promote products
#   derived from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 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 <libarch/x87.h>

.text

.global cos

cos:
	pushq %rbp
	movq %rsp, %rbp
	
	# compute cosine (using red zone)
	
	movsd %xmm0, -8(%rbp)
	fldl -8(%rbp)
	
	fcos
	
	# detect if source operand is out of range
	
	fnstsw %ax
	andw $X87_STATUS_WORD_C2_MASK, %ax
	jnz fix_range
	
		fstpl -8(%rbp)
		movsd -8(%rbp), %xmm0
		
		leave
		retq
	
	# argument reduction
	
	fix_range:
		fldpi
		fadd %st(0)
		fxch %st(1)
	
	reduce:
		fprem1
		fnstsw %ax
		andw $X87_STATUS_WORD_C2_MASK, %ax
		jnz reduce
	
	fstpl %st(1)
	fcos
	
	fstpl -8(%rbp)
	movsd -8(%rbp), %xmm0
	
	leave
	retq