#
# Copyright (c) 2014 Martin Decky
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# modification, are permitted provided that the following conditions
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#include <libarch/x87.h>

.text

.global trunc

trunc:
	pushq %rbp
	movq %rsp, %rbp
	
	# store x87 control word in the red zone
	
	fnstcw -8(%rbp)
	movw -8(%rbp), %ax
	
	# set rounding control to truncate
	# (no masking necessary for this flag)
	
	orw $X87_CONTROL_WORD_RC_TRUNCATE, %ax
	movw %ax, -16(%rbp)
	fldcw -16(%rbp)
	
	# truncate
	
	movsd %xmm0, -16(%rbp)
	fldl -16(%rbp)
	frndint
	fstpl -16(%rbp)
	movsd -16(%rbp), %xmm0
	
	# restore original control word
	
	fldcw -8(%rbp)
	
	leave
	retq