i86temps.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 192 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
*    Public License version 1.0 (the 'License'). You may not use this file
*    except in compliance with the License. BY USING THIS FILE YOU AGREE TO
*    ALL TERMS AND CONDITIONS OF THE LICENSE. A copy of the License is
*    provided with the Original Code and Modifications, and is also
*    available at www.sybase.com/developer/opensource.
*
*    The Original Code and all software distributed under the License are
*    distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
*    EXPRESS OR IMPLIED, AND SYBASE AND ALL CONTRIBUTORS HEREBY DISCLAIM
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*    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR
*    NON-INFRINGEMENT. Please see the License for the specific language
*    governing rights and limitations under the License.
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*  ========================================================================
*
* Description:  WHEN YOU FIGURE OUT WHAT THIS FILE DOES, PLEASE
*               DESCRIBE IT HERE!
*
****************************************************************************/


#include "standard.h"
#include "coderep.h"
#include "opcodes.h"
#include "procdef.h"
#include "sysmacro.h"
#include "model.h"
#include "conflict.h"
#include "savings.h"

extern  name            *DeAlias(name*);
extern  bool            UnChangeable(instruction*);
extern  bool            DoesSomething(instruction*);
extern  void            DoNothing(instruction*);
extern  type_length     PushSize(type_length);
extern  void            PropLocal(name*);

extern  proc_def        *CurrProc;
extern  bool            BlockByBlock;
extern  block           *HeadBlock;
extern  name            *Names[];
extern  byte            OptForSize;
extern  savings         Save;

static  void    AssignPushLocals( void );

extern  void    PushLocals( void ) {
/*****************************
    Assign locals which can have their initial value pushed onto the stack
*/

    if( BlockByBlock ) return;
    if( Save.store_cost[WD] <= Save.push_cost[WD] ) return;
    AssignPushLocals();
}

static  void    AssignPushLocals( void ) {
/***********************************
    Scan through HeadBlock to see if there are any leading instructions of
    the form MOV REG => temp, where temp is on the stack. We can eliminate
    the instruction (call DoNothing to mark it as unnecessary to generate)
    and then the guy that generates the prolog can come along later and
    generate PUSH REG, and adjust the SUB SP,n instruction appropriately.
    this replaces a move with a less expensive push, and if all locals
    turn out to be push locals, eliminates the SUP SP,n instruction as well
*/

    instruction *move;
    name        *src;
    name        *dst;
    type_length curr_offset;

    move = HeadBlock->ins.hd.next;
    curr_offset = 0;
    for(;;) {
        if( CurrProc->prolog_state & GENERATED_PROLOG ) break;
        if( DoesSomething( move ) ) {
            if( move->head.opcode != OP_MOV ) break;
            if( UnChangeable( move ) ) break;
            src = move->operands[ 0 ];
            dst = move->result;
            if( src->n.class != N_REGISTER ) break;
            if( _IsFloating( src->n.name_class ) ) break; /*90-Dec-17*/
            if( dst->n.class != N_TEMP ) break;
        #if _TARGET & _TARG_80386
            if( dst->n.size != 4 ) break;
        #else
            if( dst->n.size != 2 && dst->n.size != 4 ) break;
        #endif
            curr_offset -= PushSize( dst->n.size );/* assume it will be pushed*/
            if( DeAlias( dst ) != dst ) break;
            if( dst->v.usage & HAS_MEMORY ) {
                if( dst->t.location != curr_offset ) break;
            } else {
                CurrProc->targ.push_local_size += PushSize( dst->n.size );
                dst->t.location = - CurrProc->targ.push_local_size;
                dst->v.usage |= HAS_MEMORY;
                PropLocal( dst );
            }
            move->head.state = OPERANDS_NEED_WORK;
            DoNothing( move );
        }
        move = move->head.next;
    }
}


extern  void    AdjustPushLocal( name *temp ) {
/**********************************************
    Adjust the location field of a push local, and all its aliases.
    Before this routine is called, the location field just contains
    the offset relative to the first push local in the routine, not BP.
    We adjust here because the adjustment depends upon CurrProc->locals.base
    which is set by I86PROC.C, and cannot be known until we know just
    what kind of prolog we're generating.
*/

    name        *scan;

    if( ( temp->t.temp_flags & PUSH_LOCAL ) == EMPTY ) { /* if not already adjusted*/
        temp->t.location += -CurrProc->locals.size - CurrProc->locals.base;
        scan = temp->t.alias;
        while( scan != temp ) {
            scan->t.location = temp->t.location;
            scan->v.usage |= HAS_MEMORY;
            scan->t.temp_flags |= PUSH_LOCAL;
            scan = scan->t.alias;
        }
    }
}


extern  void    SetTempLocation( name *temp, type_length size ) {
/****************************************************************
    Snag a temporary with length "size" off the stack and set it's location
*/

    CurrProc->locals.size += size;
    temp->t.location = - CurrProc->locals.size
                      - CurrProc->locals.base;
}


extern  void    RelocParms( void ) {
/*****************************
    Relocate parameter locations based on what type of prolog we generated,
    how many registers were pushed on the stack, and all that other stuff
    figured out by GenProlog
*/

    name        *name;

    name = Names[ N_TEMP ];
    while( name != NULL ) {
        if( ( name->v.usage & HAS_MEMORY )
         && ( name->t.temp_flags & STACK_PARM ) ) {
            name->t.location += CurrProc->parms.base;
        }
        name = name->n.next_name;
    }
}


extern  bool    TempAllocBefore( name *t1, name *t2 ) {
/*****************************************************/

    if( (t1->t.temp_flags & USED_AS_FD) && !(t2->t.temp_flags & USED_AS_FD) ) {
        if( CurrProc->targ.sp_align ) return( FALSE );
        return( TRUE );
    }
    if( (t2->t.temp_flags & USED_AS_FD) && !(t1->t.temp_flags & USED_AS_FD) ) {
        if( CurrProc->targ.sp_align ) return( TRUE );
        return( FALSE );
    }
    if( t1->n.size < t2->n.size ) return( TRUE );
    if( t1->n.size != t2->n.size ) return( FALSE );
    /* allocate big pointers the right way 'round for LES/LDS*/
    if( t1->t.v.id == t2->t.v.id && t1->v.offset > t2->v.offset ) return( TRUE );
    return( FALSE );
}