linux/arch/ia64/lib/idiv32.S

/*
 * Copyright (C) 2000 Hewlett-Packard Co
 * Copyright (C) 2000 David Mosberger-Tang <davidm@hpl.hp.com>
 *
 * 32-bit integer division.
 *
 * This code is based on the application note entitled "Divide, Square Root
 * and Remainder Algorithms for the IA-64 Architecture".  This document
 * is available as Intel document number 248725-002 or via the web at
 * http://developer.intel.com/software/opensource/numerics/
 *
 * For more details on the theory behind these algorithms, see "IA-64
 * and Elementary Functions" by Peter Markstein; HP Professional Books
 * (http://www.goodreads.com/book/show/2019887.Ia_64_and_Elementary_Functions)
 */

#include <asm/asmmacro.h>
#include <asm/export.h>

#ifdef MODULO
# define OP	mod
#else
# define OP	div
#endif

#ifdef UNSIGNED
# define SGN	u
# define EXTEND	zxt4
# define INT_TO_FP(a,b)	fcvt.xuf.s1 a=b
# define FP_TO_INT(a,b)	fcvt.fxu.trunc.s1 a=b
#else
# define SGN
# define EXTEND	sxt4
# define INT_TO_FP(a,b)	fcvt.xf a=b
# define FP_TO_INT(a,b)	fcvt.fx.trunc.s1 a=b
#endif

#define PASTE1(a,b)	a##b
#define PASTE(a,b)	PASTE1(a,b)
#define NAME		PASTE(PASTE(__,SGN),PASTE(OP,si3))

GLOBAL_ENTRY(NAME)
	.regstk 2,0,0,0
	// Transfer inputs to FP registers.
	mov r2 = 0xffdd			// r2 = -34 + 65535 (fp reg format bias)
	EXTEND in0 = in0		// in0 = a
	EXTEND in1 = in1		// in1 = b
	;;
	setf.sig f8 = in0
	setf.sig f9 = in1
#ifdef MODULO
	sub in1 = r0, in1		// in1 = -b
#endif
	;;
	// Convert the inputs to FP, to avoid FP software-assist faults.
	INT_TO_FP(f8, f8)
	INT_TO_FP(f9, f9)
	;;
	setf.exp f7 = r2		// f7 = 2^-34
	frcpa.s1 f6, p6 = f8, f9	// y0 = frcpa(b)
	;;
(p6)	fmpy.s1 f8 = f8, f6		// q0 = a*y0
(p6)	fnma.s1 f6 = f9, f6, f1		// e0 = -b*y0 + 1 
	;;
#ifdef MODULO
	setf.sig f9 = in1		// f9 = -b
#endif
(p6)	fma.s1 f8 = f6, f8, f8		// q1 = e0*q0 + q0
(p6)	fma.s1 f6 = f6, f6, f7		// e1 = e0*e0 + 2^-34
	;;
#ifdef MODULO
	setf.sig f7 = in0
#endif
(p6)	fma.s1 f6 = f6, f8, f8		// q2 = e1*q1 + q1
	;;
	FP_TO_INT(f6, f6)		// q = trunc(q2)
	;;
#ifdef MODULO
	xma.l f6 = f6, f9, f7		// r = q*(-b) + a
	;;
#endif
	getf.sig r8 = f6		// transfer result to result register
	br.ret.sptk.many rp
END(NAME)
EXPORT_SYMBOL(NAME)