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3078a1927f
* rename old ttype variables *type to *def * rename resulttypepass to pass_typecheck * rename pass_2 to pass_generate_code git-svn-id: trunk@5077 -
80 lines
2.7 KiB
ObjectPascal
80 lines
2.7 KiB
ObjectPascal
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Common subexpression elimination on base blocks
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Copyright (c) 2005 by 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 optcse;
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{$i fpcdefs.inc}
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interface
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procedure docse(rootnode : tnode);
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implementation
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procedure docse(rootnode : tnode);
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begin
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{ create a linear list of nodes }
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{ create hash values }
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{ sort by hash values, taking care of nf_csebarrier and keeping the
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original order of the nodes }
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{ compare nodes with equal hash values }
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{ search barrier }
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for i:=0 to nodelist.length-1 do
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begin
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{ and then search backward so we get always the largest equal trees }
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j:=i+1;
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{ collect equal nodes }
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while (j<=nodelist.length-1) and
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nodelist[i].docompare(nodelist[j]) do
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inc(j);
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dec(j);
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if j>i then
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begin
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{ cse found }
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{ create temp. location }
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{ replace first node by
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- temp. creation
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- expression calculation
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- assignment of expression to temp. }
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tempnode:=ctempcreatenode.create(nodelist[i].resultdef,nodelist[i].resultdef.size,tt_persistent,
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nodelist[i].resultdef.is_intregable or nodelist[i].resultdef.is_fpuregable);
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addstatement(createstatement,tempnode);
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addstatement(createstatement,cassignmentnode.create(ctemprefnode.create(tempnode),
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caddrnode.create_internal(para.left)));
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para.left := ctypeconvnode.create_internal(cderefnode.create(ctemprefnode.create(tempnode)),para.left.resultdef);
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addstatement(deletestatement,ctempdeletenode.create(tempnode));
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{ replace next nodes by loading the temp. reference }
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{ replace last node by loading the temp. reference and
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delete the temp. }
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end;
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end;
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end;
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end.
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