LXR linux/arch/ia64/lib/idiv32.S

   1/*
   2 * Copyright (C) 2000 Hewlett-Packard Co
   3 * Copyright (C) 2000 David Mosberger-Tang <davidm@hpl.hp.com>
   4 *
   5 * 32-bit integer division.
   6 *
   7 * This code is based on the application note entitled "Divide, Square Root
   8 * and Remainder Algorithms for the IA-64 Architecture".  This document
   9 * is available as Intel document number 248725-002 or via the web at
  10 * http://developer.intel.com/software/opensource/numerics/
  11 *
  12 * For more details on the theory behind these algorithms, see "IA-64
  13 * and Elementary Functions" by Peter Markstein; HP Professional Books
  14 * (http://www.hp.com/go/retailbooks/)
  15 */
  16
  17#include <asm/asmmacro.h>
  18
  19#ifdef MODULO
  20# define OP     mod
  21#else
  22# define OP     div
  23#endif
  24
  25#ifdef UNSIGNED
  26# define SGN    u
  27# define EXTEND zxt4
  28# define INT_TO_FP(a,b) fcvt.xuf.s1 a=b
  29# define FP_TO_INT(a,b) fcvt.fxu.trunc.s1 a=b
  30#else
  31# define SGN
  32# define EXTEND sxt4
  33# define INT_TO_FP(a,b) fcvt.xf a=b
  34# define FP_TO_INT(a,b) fcvt.fx.trunc.s1 a=b
  35#endif
  36
  37#define PASTE1(a,b)     a##b
  38#define PASTE(a,b)      PASTE1(a,b)
  39#define NAME            PASTE(PASTE(__,SGN),PASTE(OP,si3))
  40
  41GLOBAL_ENTRY(NAME)
  42        .regstk 2,0,0,0
  43        // Transfer inputs to FP registers.
  44        mov r2 = 0xffdd                 // r2 = -34 + 65535 (fp reg format bias)
  45        EXTEND in0 = in0                // in0 = a
  46        EXTEND in1 = in1                // in1 = b
  47        ;;
  48        setf.sig f8 = in0
  49        setf.sig f9 = in1
  50#ifdef MODULO
  51        sub in1 = r0, in1               // in1 = -b
  52#endif
  53        ;;
  54        // Convert the inputs to FP, to avoid FP software-assist faults.
  55        INT_TO_FP(f8, f8)
  56        INT_TO_FP(f9, f9)
  57        ;;
  58        setf.exp f7 = r2                // f7 = 2^-34
  59        frcpa.s1 f6, p6 = f8, f9        // y0 = frcpa(b)
  60        ;;
  61(p6)    fmpy.s1 f8 = f8, f6             // q0 = a*y0
  62(p6)    fnma.s1 f6 = f9, f6, f1         // e0 = -b*y0 + 1 
  63        ;;
  64#ifdef MODULO
  65        setf.sig f9 = in1               // f9 = -b
  66#endif
  67(p6)    fma.s1 f8 = f6, f8, f8          // q1 = e0*q0 + q0
  68(p6)    fma.s1 f6 = f6, f6, f7          // e1 = e0*e0 + 2^-34
  69        ;;
  70#ifdef MODULO
  71        setf.sig f7 = in0
  72#endif
  73(p6)    fma.s1 f6 = f6, f8, f8          // q2 = e1*q1 + q1
  74        ;;
  75        FP_TO_INT(f6, f6)               // q = trunc(q2)
  76        ;;
  77#ifdef MODULO
  78        xma.l f6 = f6, f9, f7           // r = q*(-b) + a
  79        ;;
  80#endif
  81        getf.sig r8 = f6                // transfer result to result register
  82        br.ret.sptk.many rp
  83END(NAME)
  84