overlap.c

来自「开放源码的编译器open watcom 1.6.0版的源代码」· C语言 代码 · 共 97 行

/****************************************************************************
*
*                            Open Watcom Project
*
*    Portions Copyright (c) 1983-2002 Sybase, Inc. All Rights Reserved.
*
*  ========================================================================
*
*    This file contains Original Code and/or Modifications of Original
*    Code as defined in and that are subject to the Sybase Open Watcom
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*    except in compliance with the License. BY USING THIS FILE YOU AGREE TO
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* Description:  WHEN YOU FIGURE OUT WHAT THIS FILE DOES, PLEASE
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****************************************************************************/


#include "standard.h"
#include "coderep.h"
#include "regset.h"

extern  name    *DeAlias( name * );
extern  bool    Overlaps( name *, name * );

static  bool    Conflicts( type_length start, type_length end,
                        type_length start2, type_length end2 ) {
/**************************************************************/
    if( ( start2 >= start && start2 <= end ) ||
        ( end2 >= start && end2 <= end ) ) {
        return( TRUE );
    }
    return( FALSE );
}

static  bool    ovNo( name *op1, name *op2 ) {
    op1 = op2;
    return( FALSE );
}

static  bool    ovYes( name *op1, name *op2 ) {
    op1 = op2;
    return( TRUE );
}

static  bool    ovTemp( name *op1, name *op2 ) {
    if( DeAlias( op1 ) == DeAlias( op2 ) ) {
        return( Conflicts( op1->v.offset, op1->v.offset + op1->n.size,
                    op2->v.offset, op2->v.offset + op2->n.size ) );
    }
    return( FALSE );
}

static  bool    ovReg( name *op1, name *op2 ) {
    return( HW_Ovlap( op1->r.reg, op2->r.reg ) );
}

static  bool    ovIndex( name *op1, name *op2 ) {
    /* this is overly pessimistic, but we shouldn't see mem->mem moves anyway */
    op1 = op2;
    return( TRUE );
}

static  bool    ovUses( name *op1, name *index ) {
    return( Overlaps( index->i.index, op1 ) ||
            Overlaps( index->i.base, op1 ) );
}

static  bool    (*OverlapTable[N_INDEXED+1][N_INDEXED+1])( name *, name * ) = {
/* result       op ->   N_CONST N_MEM   N_TEMP  N_REG   N_INDEX */
/* N_CONSTANT   */   {  ovNo,   ovNo,   ovNo,   ovNo,   ovNo },
/* N_MEMORY     */   {  ovNo,   ovYes,  ovNo,   ovNo,   ovNo },
/* N_TEMP       */   {  ovNo,   ovNo,   ovTemp, ovNo,   ovUses },
/* N_REGISTER   */   {  ovNo,   ovNo,   ovNo,   ovReg,  ovUses },
/* N_INDEX      */   {  ovNo,   ovNo,   ovNo,   ovNo,   ovIndex } };

extern  bool    Overlaps( name *result, name *op ) {
/**************************************************/
    if( result == NULL || op == NULL ) return( FALSE );
    if( result == op ) return( TRUE );
    return( OverlapTable[result->n.class][op->n.class]( result, op ) );
}