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123 lines
4.6 KiB
ObjectPascal
123 lines
4.6 KiB
ObjectPascal
{
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Dead store elimination
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Copyright (c) 2005-2012 by Jeppe Johansen and Florian Klaempfl
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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****************************************************************************
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}
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unit optdeadstore;
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{$i fpcdefs.inc}
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{ $define DEBUG_DEADSTORE}
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interface
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uses
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node;
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function do_optdeadstoreelim(var rootnode : tnode) : tnode;
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implementation
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uses
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verbose,globtype,globals,
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fmodule,
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procinfo,pass_1,
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nutils,
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nbas,nld,nmem,nflw,nset,
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optbase,
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symsym,symconst;
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function deadstoreelim(var n: tnode; arg: pointer): foreachnoderesult;
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var
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a: tassignmentnode;
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redundant: boolean;
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begin
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result:=fen_true;
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if (n.nodetype=statementn) and
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assigned(tstatementnode(n).statement) then
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begin
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if tstatementnode(n).statement.nodetype=assignn then
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begin
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a:=tassignmentnode(tstatementnode(n).statement);
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{ we need to have dfa for the node }
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if assigned(a.left.optinfo) and
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(a.left.optinfo^.index<>aword(-1)) and
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{ node must be either a local or parameter load node }
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(a.left.nodetype=loadn) and
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{ its address cannot have escaped the current routine }
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not(tabstractvarsym(tloadnode(a.left).symtableentry).addr_taken) and
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((
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(tloadnode(a.left).symtableentry.typ=localvarsym) and
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(tloadnode(a.left).symtable=current_procinfo.procdef.localst)) or
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((tloadnode(a.left).symtableentry.typ=paravarsym) and
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(tloadnode(a.left).symtable=current_procinfo.procdef.parast) and
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(tparavarsym(tloadnode(a.left).symtableentry).varspez in [vs_const,vs_value])) or
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((tloadnode(a.left).symtableentry.typ=staticvarsym) and
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(tloadnode(a.left).symtable.symtabletype=staticsymtable) and
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(current_procinfo.procdef.proctypeoption<>potype_unitinit)
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)
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) and
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((a.right.nodetype in [niln,stringconstn,pointerconstn,setconstn,guidconstn]) or
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((a.right.nodetype=ordconstn) and not(cs_check_range in current_settings.localswitches)) or
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((a.right.nodetype=realconstn) and not(cs_ieee_errors in current_settings.localswitches)) or
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((cs_opt_dead_values in current_settings.optimizerswitches) and not(might_have_sideeffects(a.right)))
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) then
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begin
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redundant:=not(assigned(a.successor)) or not(DFASetIn(a.successor.optinfo^.life,a.left.optinfo^.index));
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if redundant then
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begin
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{$ifdef DEBUG_DEADSTORE}
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writeln('************************** Redundant write *********************************');
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printnode(a);
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writeln('****************************************************************************');
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{$endif DEBUG_DEADSTORE}
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pboolean(arg)^:=true;
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tstatementnode(n).statement.free;
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tstatementnode(n).statement:=cnothingnode.create;
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Exclude(tstatementnode(n).flags, nf_pass1_done);
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do_firstpass(n);
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end
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end;
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end;
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end;
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end;
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function do_optdeadstoreelim(var rootnode: tnode): tnode;
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var
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changed: boolean;
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begin
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if not(pi_dfaavailable in current_procinfo.flags) then
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internalerror(2013110201);
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if not current_procinfo.has_nestedprocs then
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begin
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changed:=false;
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foreachnodestatic(pm_postprocess, rootnode, @deadstoreelim, @changed);
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end;
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result:=rootnode;
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end;
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end.
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