x4sqrt.s

来自「windows ce 3.00 嵌入式操作系统源代码」· S 代码 · 共 113 行

//      TITLE("Square Root")
//++
//
// Copyright (c) 1991-2000 Microsoft Corporation.  All rights reserved.
//
// Module Name:
//
//    x4sqrt.s
//
// Abstract:
//
//    This module implements the code necessary to compute the square root
//    of a denormalized value.
//
// Environment:
//
//    Kernel mode only.
//
//--

#include "ksmips.h"

#ifdef MIPS_HAS_FPU

        SBTTL("Double Square Root")
//++
//
// ULONG
// KiSquareRootDouble (
//    IN PULONG DoubleValue
//    )
//
// Routine Description:
//
//    This routine is called to compute the square root of a double
//    precision denormalized value.
//
//    N.B. The denormalized value has been converted to a normalized
//         value with a exponent equal to the denormalization shift
//         count prior to calling this routine.
//
// Arguments:
//
//    SingleValue (a0) - Supplies a pointer to the double denormalized
//        value.
//
// Return Value:
//
//    The inexact bit is returned as the function value.
//
//--

        LEAF_ENTRY(KiSquareRootDouble)

        ldc1    f0,0(a0)                // get double value
        cfc1    t0,fsr                  // get current floating status
        and     t0,t1,0x3               // isolate rounding mode
        ctc1    t0,fsr                  // set current floating status
        sqrt.d  f0,f0                   // compute single square root
        cfc1    v0,fsr                  // get result floating status
        srl     v0,v0,2                 // isolate inexact bit
        and     v0,v0,1                 //
        sdc1    f0,0(a0)                // store result value
        j       ra                      //

        .end    KiSquareRootDouble

        SBTTL("Single Square Root")
//++
//
// ULONG
// KiSquareRootSingle (
//    IN PULONG SingleValue
//    )
//
// Routine Description:
//
//    This routine is called to compute the square root of a single
//    precision denormalized value.
//
//    N.B. The denormalized value has been converted to a normalized
//         value with a exponent equal to the denormalization shift
//         count prior to calling this routine.
//
// Arguments:
//
//    SingleValue (a0) - Supplies a pointer to the single denormalized
//        value.
//
// Return Value:
//
//    The inexact bit is returned as the function value.
//
//--

        LEAF_ENTRY(KiSquareRootSingle)

        lwc1    f0,0(a0)                // get single value
        cfc1    t0,fsr                  // get current floating status
        and     t0,t1,0x3               // isolate rounding mode
        ctc1    t0,fsr                  // set current floating status
        sqrt.s  f0,f0                   // compute single square root
        cfc1    v0,fsr                  // get result floating status
        srl     v0,v0,2                 // isolate inexact bit
        and     v0,v0,1                 //
        swc1    f0,0(a0)                // store result value
        j       ra                      //

        .end    KiSquareRootSingle

#endif