cgbkretn.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 96 行

/****************************************************************************
*
*                            Open Watcom Project
*
*    Portions Copyright (c) 1983-2002 Sybase, Inc. All Rights Reserved.
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*  ========================================================================
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*    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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* Description:  WHEN YOU FIGURE OUT WHAT THIS FILE DOES, PLEASE
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****************************************************************************/


#include "plusplus.h"
#include "cgfront.h"
#include "cgback.h"
#include "codegen.h"
#include "cgbackut.h"


boolean CgRetnOptForFile        // TEST IF RETURN OPTIMIZATION FOR FILE
    ( CGFILE* file_ctl )        // - file control
{
    return file_ctl->opt_retn_val || file_ctl->opt_retn_ref;
}


boolean CgRetnOptActive         // TEST IF RETURN OPTIMIZATION ACTIVE FOR FILE
    ( FN_CTL* fctl )            // - file-activation control
{
    CGFILE* file_ctl;           // - file control

    file_ctl = fctl->cgfile;
    return CgRetnOptForFile( file_ctl )
        && !( fctl->debug_info && ( GenSwitches & DBG_LOCALS ) );
}


boolean CgRetnOptIsOptVar       // TEST IF SYMBOL IS RETURN-OPTIMIZATION VAR
    ( FN_CTL* fctl              // - file-activation control
    , SYMBOL var )              // - var. to be tested
{
    return CgRetnOptActive( fctl )
        && var == fctl->cgfile->opt_retn;

}


void CgRetnOpt_RETNOPT_BEG      // PROCESS IC_RETNOPT_BEG
    ( FN_CTL* fctl )            // - file-activation control
{
    if( CgRetnOptActive( fctl ) ) {
        CgioReadICUntilOpcode( fctl->cgfile, IC_RETNOPT_END );
    }
}


// NOTE: this is only processed by back-end
//
// We cannot easily determine whether a function will optimize away the
// return during call-graph processing, so we must be conservative.
//
// Codes are skipped when "var" is optimized away.
//
void CgRetnOpt_RETNOPT_VAR      // PROCESS IC_RETNOPT_VAR
    ( FN_CTL* fctl              // - file-activation control
    , SYMBOL var )              // - variable
{
    CGFILE* file_ctl;           // - file control

    file_ctl = fctl->cgfile;
    if( var == file_ctl->opt_retn
     && CgRetnOptActive( fctl ) ) {
        CgioReadICUntilOpcode( file_ctl, IC_RETNOPT_END );
    }
}