root/arch/ia64/lib/idiv32.S

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * Copyright (C) 2000 Hewlett-Packard Co
   4  * Copyright (C) 2000 David Mosberger-Tang <davidm@hpl.hp.com>
   5  *
   6  * 32-bit integer division.
   7  *
   8  * This code is based on the application note entitled "Divide, Square Root
   9  * and Remainder Algorithms for the IA-64 Architecture".  This document
  10  * is available as Intel document number 248725-002 or via the web at
  11  * http://developer.intel.com/software/opensource/numerics/
  12  *
  13  * For more details on the theory behind these algorithms, see "IA-64
  14  * and Elementary Functions" by Peter Markstein; HP Professional Books
  15  * (http://www.goodreads.com/book/show/2019887.Ia_64_and_Elementary_Functions)
  16  */
  17 
  18 #include <asm/asmmacro.h>
  19 #include <asm/export.h>
  20 
  21 #ifdef MODULO
  22 # define OP     mod
  23 #else
  24 # define OP     div
  25 #endif
  26 
  27 #ifdef UNSIGNED
  28 # define SGN    u
  29 # define EXTEND zxt4
  30 # define INT_TO_FP(a,b) fcvt.xuf.s1 a=b
  31 # define FP_TO_INT(a,b) fcvt.fxu.trunc.s1 a=b
  32 #else
  33 # define SGN
  34 # define EXTEND sxt4
  35 # define INT_TO_FP(a,b) fcvt.xf a=b
  36 # define FP_TO_INT(a,b) fcvt.fx.trunc.s1 a=b
  37 #endif
  38 
  39 #define PASTE1(a,b)     a##b
  40 #define PASTE(a,b)      PASTE1(a,b)
  41 #define NAME            PASTE(PASTE(__,SGN),PASTE(OP,si3))
  42 
  43 GLOBAL_ENTRY(NAME)
  44         .regstk 2,0,0,0
  45         // Transfer inputs to FP registers.
  46         mov r2 = 0xffdd                 // r2 = -34 + 65535 (fp reg format bias)
  47         EXTEND in0 = in0                // in0 = a
  48         EXTEND in1 = in1                // in1 = b
  49         ;;
  50         setf.sig f8 = in0
  51         setf.sig f9 = in1
  52 #ifdef MODULO
  53         sub in1 = r0, in1               // in1 = -b
  54 #endif
  55         ;;
  56         // Convert the inputs to FP, to avoid FP software-assist faults.
  57         INT_TO_FP(f8, f8)
  58         INT_TO_FP(f9, f9)
  59         ;;
  60         setf.exp f7 = r2                // f7 = 2^-34
  61         frcpa.s1 f6, p6 = f8, f9        // y0 = frcpa(b)
  62         ;;
  63 (p6)    fmpy.s1 f8 = f8, f6             // q0 = a*y0
  64 (p6)    fnma.s1 f6 = f9, f6, f1         // e0 = -b*y0 + 1 
  65         ;;
  66 #ifdef MODULO
  67         setf.sig f9 = in1               // f9 = -b
  68 #endif
  69 (p6)    fma.s1 f8 = f6, f8, f8          // q1 = e0*q0 + q0
  70 (p6)    fma.s1 f6 = f6, f6, f7          // e1 = e0*e0 + 2^-34
  71         ;;
  72 #ifdef MODULO
  73         setf.sig f7 = in0
  74 #endif
  75 (p6)    fma.s1 f6 = f6, f8, f8          // q2 = e1*q1 + q1
  76         ;;
  77         FP_TO_INT(f6, f6)               // q = trunc(q2)
  78         ;;
  79 #ifdef MODULO
  80         xma.l f6 = f6, f9, f7           // r = q*(-b) + a
  81         ;;
  82 #endif
  83         getf.sig r8 = f6                // transfer result to result register
  84         br.ret.sptk.many rp
  85 END(NAME)
  86 EXPORT_SYMBOL(NAME)