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{
Common subexpression elimination on base blocks
Copyright (c) 2005-2012 by Florian Klaempfl
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
****************************************************************************
}
unit optcse;
{$i fpcdefs.inc}
{ $define csedebug}
{ $define csestats}
interface
uses
node;
{
the function creates non optimal code so far:
- call para nodes are cse barriers because they can be reordered and thus the
temp. creation could be done too late
- the cse knows nothing about register pressure. In case of high register pressure, cse might
have a negative impact
- the list of cseinvariant node types and inline numbers is not complete yet
Further, it could be done probably in a faster way though the complexity can't probably not reduced
}
function do_optcse(var rootnode : tnode) : tnode;
implementation
uses
globtype,globals,
cutils,cclasses,
nutils,compinnr,
nbas,nld,ninl,ncal,nadd,nmem,
pass_1,
symconst,symdef,symsym,
defutil,
optbase;
const
cseinvariant : set of tnodetype = [addn,muln,subn,divn,slashn,modn,andn,orn,xorn,notn,vecn,
derefn,equaln,unequaln,ltn,gtn,lten,gten,typeconvn,subscriptn,
inn,symdifn,shrn,shln,ordconstn,realconstn,unaryminusn,pointerconstn,stringconstn,setconstn,niln,
setelementn,{arrayconstructorn,arrayconstructorrangen,}
isn,asn,starstarn,nothingn,temprefn,loadparentfpn {,callparan},assignn,addrn];
function searchsubdomain(var n:tnode; arg: pointer) : foreachnoderesult;
begin
if (n.nodetype in cseinvariant) or
((n.nodetype=inlinen) and
(tinlinenode(n).inlinenumber in [in_length_x,in_assigned_x,in_sqr_real,in_sqrt_real,in_sin_real,in_cos_real,in_abs_long,
in_abs_real,in_exp_real,in_ln_real,in_pi_real,in_popcnt_x,in_arctan_real,in_round_real,in_trunc_real,
{ cse on fma will still not work because it would require proper handling of call nodes
with more than one parameter }
in_fma_single,in_fma_double,in_fma_extended,in_fma_float128])
) or
((n.nodetype=callparan) and not(assigned(tcallparanode(n).right))) or
((n.nodetype=loadn) and
not((tloadnode(n).symtableentry.typ in [staticvarsym,localvarsym,paravarsym]) and
(vo_volatile in tabstractvarsym(tloadnode(n).symtableentry).varoptions))
) then
result:=fen_true
else
begin
pboolean(arg)^:=false;
result:=fen_norecurse_true;
end;
end;
type
tlists = record
nodelist : tfplist;
locationlist : tfplist;
equalto : tfplist;
refs : tfplist;
avail : TDFASet;
end;
plists = ^tlists;
{ collectnodes needs the address of itself to call foreachnodestatic,
so we need a wrapper because @<func> inside <func doesn't work }
function collectnodes(var n:tnode; arg: pointer) : foreachnoderesult;forward;
function collectnodes2(var n:tnode; arg: pointer) : foreachnoderesult;
begin
result:=collectnodes(n,arg);
end;
function collectnodes(var n:tnode; arg: pointer) : foreachnoderesult;
{ when compiling a tree like
and
/ \
and C
/ \
A B
all expressions of B are available during evaluation of C. However considerung the whole expression,
values of B and C might not be available due to short boolean evaluation.
So recurseintobooleanchain detectes such chained and/or expressions and makes sub-expressions of B
available during the evaluation of C
firstleftend is later used to remove all sub expressions of B and C by storing the expression count
in the cse table after handling A
}
var
firstleftend : longint;
procedure recurseintobooleanchain(t : tnodetype;n : tnode);
begin
if (tbinarynode(n).left.nodetype=t) and is_boolean(tbinarynode(n).left.resultdef) then
recurseintobooleanchain(t,tbinarynode(n).left)
else
foreachnodestatic(pm_postprocess,tbinarynode(n).left,@collectnodes2,arg);
firstleftend:=min(plists(arg)^.nodelist.count,firstleftend);
foreachnodestatic(pm_postprocess,tbinarynode(n).right,@collectnodes2,arg);
end;
var
i : longint;
begin
result:=fen_false;
{ don't add the tree below an untyped const parameter: there is
no information available that this kind of tree actually needs
to be addresable, this could be improved }
{ the nodes below a type conversion node created for an absolute
reference cannot be handled separately, because the absolute reference
may have special requirements (no regability, must be in memory, ...)
}
if (((n.nodetype=callparan) and
(tcallparanode(n).left.resultdef.typ=formaldef) and
(tcallparanode(n).parasym.varspez=vs_const)) or
((n.nodetype=typeconvn) and
(nf_absolute in n.flags))
) then
begin
result:=fen_norecurse_false;
exit;
end;
if
{ node possible to add? }
assigned(n.resultdef) and
(
{ regable expressions }
(actualtargetnode(@n)^.flags*[nf_write,nf_modify,nf_address_taken]=[]) and
((((tstoreddef(n.resultdef).is_intregable or tstoreddef(n.resultdef).is_fpuregable or tstoreddef(n.resultdef).is_const_intregable) and
{ is_int/fpuregable allows arrays and records to be in registers, cse cannot handle this }
(not(n.resultdef.typ in [arraydef,recorddef]))) or
is_dynamic_array(n.resultdef) or
((n.resultdef.typ in [arraydef,recorddef]) and not(is_special_array(tstoreddef(n.resultdef))) and not(tstoreddef(n.resultdef).is_intregable) and not(tstoreddef(n.resultdef).is_fpuregable))
) and
{ same for voiddef }
not(is_void(n.resultdef)) and
{ adding tempref and callpara nodes itself is worthless but
their complexity is probably <= 1 anyways
neither add setelementn nodes because the compiler sometimes depends on the fact
that a certain node stays a setelementn, this does not hurt either because
setelementn nodes itself generate no real code (except moving data into register) }
not(n.nodetype in [temprefn,callparan,setelementn]) and
{ node worth to add?
We consider almost every node because even loading a variables from
a register instead of memory is more beneficial. This behaviour should
not increase register pressure because if a variable is already
in a register, the reg. allocator can merge the nodes. If a variable
is loaded from memory, loading this variable and spilling another register
should not add a speed penalty.
}
{
load nodes are not considered if they load para or local symbols from the
current stack frame, those are in registers anyways if possible
}
(not(actualtargetnode(@n)^.nodetype=loadn) or
not(tloadnode(actualtargetnode(@n)^).symtableentry.typ in [paravarsym,localvarsym,staticvarsym]) or
{ apply cse on non-regable variables }
((tloadnode(actualtargetnode(@n)^).symtableentry.typ in [paravarsym,localvarsym,staticvarsym]) and
not(tabstractvarsym(tloadnode(actualtargetnode(@n)^).symtableentry).is_regvar(false)) and
not(vo_volatile in tabstractvarsym(tloadnode(actualtargetnode(@n)^).symtableentry).varoptions)) or
(node_complexity(n)>1)
) and
{
Const nodes however are only considered if their complexity is >1
This might be the case for the risc architectures if they need
more than one instruction to load this particular value
}
(not(is_constnode(n)) or (node_complexity(n)>1)))
{$if not(defined(i386)) and not(defined(i8086))}
or
{ store reference of expression? }
{ loading the address of a global symbol takes typically more than
one instruction on every platform except i8086/i386
so consider in this case loading the address of the data
}
(((n.resultdef.typ in [arraydef,recorddef]) or is_object(n.resultdef)) and not(is_dynamic_array(n.resultdef)) and
(n.nodetype=loadn) and
(tloadnode(n).symtableentry.typ=staticvarsym)
)
{$endif not(defined(i386)) and not(defined(i8086))}
) then
begin
plists(arg)^.nodelist.Add(n);
plists(arg)^.locationlist.Add(@n);
plists(arg)^.refs.Add(nil);
plists(arg)^.equalto.Add(pointer(-1));
DFASetInclude(plists(arg)^.avail,plists(arg)^.nodelist.count-1);
for i:=0 to plists(arg)^.nodelist.count-2 do
begin
if tnode(plists(arg)^.nodelist[i]).isequal(n) and DFASetIn(plists(arg)^.avail,i) then
begin
{ use always the first occurence }
if plists(arg)^.equalto[i]<>pointer(-1) then
plists(arg)^.equalto[plists(arg)^.nodelist.count-1]:=plists(arg)^.equalto[i]
else
plists(arg)^.equalto[plists(arg)^.nodelist.count-1]:=pointer(ptrint(i));
plists(arg)^.refs[i]:=pointer(plists(arg)^.refs[i])+1;
{ tree has been found, no need to search further,
sub-trees have been added by the first occurence of
the tree already }
result:=fen_norecurse_false;
break;
end;
end;
end;
{ boolean and/or require a special handling: after evaluating the and/or node,
the expressions of the right side might not be available due to short boolean
evaluation, so after handling the right side, mark those expressions
as unavailable }
if (n.nodetype in [orn,andn]) and is_boolean(taddnode(n).left.resultdef) then
begin
firstleftend:=high(longint);
recurseintobooleanchain(n.nodetype,n);
for i:=firstleftend to plists(arg)^.nodelist.count-1 do
DFASetExclude(plists(arg)^.avail,i);
result:=fen_norecurse_false;
end;
{$ifdef cpuhighleveltarget}
{ The high level targets use the functionality from ncgnstld for
nested accesses, and that one stores the complete location of the
nested variable in tloadnode.left rather than only the location of
the parent context containing it. This causes problems with the
CSE in case the nested variable is used as an lvalue, so disable
CSE in that case
}
if (n.nodetype=loadn) and assigned(tloadnode(n).left) then
result:=fen_norecurse_false;
{$endif}
end;
function searchcsedomain(var n: tnode; arg: pointer) : foreachnoderesult;
var
csedomain : boolean;
lists : tlists;
templist : tfplist;
i : longint;
def : tstoreddef;
nodes : tblocknode;
creates,
statements : tstatementnode;
deletetemp : ttempdeletenode;
hp : ttempcreatenode;
addrstored : boolean;
hp2 : tnode;
begin
result:=fen_false;
nodes:=nil;
if n.nodetype in cseinvariant then
begin
csedomain:=true;
foreachnodestatic(pm_postprocess,n,@searchsubdomain,@csedomain);
if not(csedomain) then
begin
{ try to transform the tree to get better cse domains, consider:
+
/ \
+ C
/ \
A B
if A is not cse'able but B and C are, then the compiler cannot do cse so the tree is transformed into
+
/ \
A +
/ \
B C
Because A could be another tree of this kind, the whole process is done in a while loop
}
if (n.nodetype in [andn,orn,addn,muln]) and
(n.nodetype=tbinarynode(n).left.nodetype) and
{ do is optimizations only for integers, reals (no currency!), vectors, sets or booleans }
(is_integer(n.resultdef) or is_real(n.resultdef) or is_vector(n.resultdef) or is_set(n.resultdef) or
is_boolean(n.resultdef)) and
{ either if fastmath is on }
((cs_opt_fastmath in current_settings.optimizerswitches) or
{ or for the logical operators, they cannot overflow }
(n.nodetype in [andn,orn]) or
{ or for integers if range checking is off }
((is_integer(n.resultdef) and
(n.localswitches*[cs_check_range,cs_check_overflow]=[]) and
(tbinarynode(n).left.localswitches*[cs_check_range,cs_check_overflow]=[]))) or
{ for sets, we can do this always }
(is_set(n.resultdef))
) then
while (n.nodetype=tbinarynode(n).left.nodetype) and
{ the resulttypes of the operands we'll swap must be equal,
required in case of a 32x32->64 multiplication, then we
cannot swap out one of the 32 bit operands for a 64 bit one
}
(tbinarynode(tbinarynode(n).left).left.resultdef=tbinarynode(n).left.resultdef) and
(tbinarynode(n).left.resultdef=tbinarynode(n).right.resultdef) do
begin
csedomain:=true;
foreachnodestatic(pm_postprocess,tbinarynode(n).right,@searchsubdomain,@csedomain);
if csedomain then
begin
csedomain:=true;
foreachnodestatic(pm_postprocess,tbinarynode(tbinarynode(n).left).right,@searchsubdomain,@csedomain);
if csedomain then
begin
hp2:=tbinarynode(tbinarynode(n).left).left;
tbinarynode(tbinarynode(n).left).left:=tbinarynode(tbinarynode(n).left).right;
tbinarynode(tbinarynode(n).left).right:=tbinarynode(n).right;
tbinarynode(n).right:=tbinarynode(n).left;
tbinarynode(n).left:=hp2;
{ the transformed tree could result in new possibilities to fold constants
so force a firstpass on the root node }
exclude(tbinarynode(n).right.flags,nf_pass1_done);
do_firstpass(tbinarynode(n).right);
end
else
break;
end
else
break;
end;
end
else
begin
statements:=nil;
result:=fen_norecurse_true;
{$ifdef csedebug}
writeln('============ cse domain ==================');
printnode(output,n);
writeln('Complexity: ',node_complexity(n));
{$endif csedebug}
lists.nodelist:=tfplist.create;
lists.locationlist:=tfplist.create;
lists.equalto:=tfplist.create;
lists.refs:=tfplist.create;
foreachnodestatic(pm_postprocess,n,@collectnodes,@lists);
templist:=tfplist.create;
templist.count:=lists.nodelist.count;
{ check all nodes if one is used more than once }
for i:=0 to lists.nodelist.count-1 do
begin
{ current node used more than once? }
if assigned(lists.refs[i]) then
begin
if not(assigned(statements)) then
begin
nodes:=internalstatements(statements);
addstatement(statements,internalstatements(creates));
end;
def:=tstoreddef(tnode(lists.nodelist[i]).resultdef);
{ we cannot handle register stored records or array in CSE yet
but we can store their reference }
addrstored:=((def.typ in [arraydef,recorddef]) or is_object(def)) and not(is_dynamic_array(def));
if addrstored then
templist[i]:=ctempcreatenode.create_value(cpointerdef.getreusable(def),voidpointertype.size,tt_persistent,
true,caddrnode.create_internal(tnode(lists.nodelist[i])))
else
templist[i]:=ctempcreatenode.create_value(def,def.size,tt_persistent,
def.is_intregable or def.is_fpuregable or def.is_const_intregable,tnode(lists.nodelist[i]));
{ the value described by the temp. is immutable and the temp. can be always in register
ttempcreatenode.create normally takes care of the register location but it does not
know about immutability so it cannot take care of managed types }
ttempcreatenode(templist[i]).includetempflag(ti_const);
ttempcreatenode(templist[i]).includetempflag(ti_may_be_in_reg);
{ make debugging easier and set temp. location to the original location }
tnode(templist[i]).fileinfo:=tnode(lists.nodelist[i]).fileinfo;
addstatement(creates,tnode(templist[i]));
{ the delete node has no semantic use yet, it is just used to clean up memory }
deletetemp:=ctempdeletenode.create(ttempcreatenode(templist[i]));
deletetemp.includetempflag(ti_cleanup_only);
addstatement(tstatementnode(arg^),deletetemp);
{ make debugging easier and set temp. location to the original location }
creates.fileinfo:=tnode(lists.nodelist[i]).fileinfo;
hp:=ttempcreatenode(templist[i]);
do_firstpass(tnode(hp));
templist[i]:=hp;
if addrstored then
pnode(lists.locationlist[i])^:=cderefnode.Create(ctemprefnode.create(ttempcreatenode(templist[i])))
else
pnode(lists.locationlist[i])^:=ctemprefnode.create(ttempcreatenode(templist[i]));
{ make debugging easier and set temp. location to the original location }
pnode(lists.locationlist[i])^.fileinfo:=tnode(lists.nodelist[i]).fileinfo;
do_firstpass(pnode(lists.locationlist[i])^);
{$ifdef csedebug}
printnode(output,statements);
{$endif csedebug}
end
{ current node reference to another node? }
else if lists.equalto[i]<>pointer(-1) then
begin
def:=tstoreddef(tnode(lists.nodelist[i]).resultdef);
{ we cannot handle register stored records or array in CSE yet
but we can store their reference }
addrstored:=((def.typ in [arraydef,recorddef]) or is_object(def)) and not(is_dynamic_array(def));
{$if defined(csedebug) or defined(csestats)}
writeln;
writeln('!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!');
writeln('Complexity: ',node_complexity(tnode(lists.nodelist[i])),' Node ',i,' equals Node ',ptrint(lists.equalto[i]));
printnode(output,tnode(lists.nodelist[i]));
printnode(output,tnode(lists.nodelist[ptrint(lists.equalto[i])]));
writeln('!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!');
writeln;
{$endif defined(csedebug) or defined(csestats)}
templist[i]:=templist[ptrint(lists.equalto[i])];
if addrstored then
pnode(lists.locationlist[i])^:=cderefnode.Create(ctemprefnode.create(ttempcreatenode(templist[ptrint(lists.equalto[i])])))
else
pnode(lists.locationlist[i])^:=ctemprefnode.create(ttempcreatenode(templist[ptrint(lists.equalto[i])]));
{ make debugging easier and set temp. location to the original location }
pnode(lists.locationlist[i])^.fileinfo:=tnode(lists.nodelist[i]).fileinfo;
do_firstpass(pnode(lists.locationlist[i])^);
end;
end;
{ clean up unused trees }
for i:=0 to lists.nodelist.count-1 do
if lists.equalto[i]<>pointer(-1) then
tnode(lists.nodelist[i]).free;
{$ifdef csedebug}
writeln('nodes: ',lists.nodelist.count);
writeln('==========================================');
{$endif csedebug}
lists.nodelist.free;
lists.locationlist.free;
lists.equalto.free;
lists.refs.free;
templist.free;
if assigned(statements) then
begin
{ call para nodes need a special handling because
they can be only children nodes of call nodes
so the initialization code is inserted below the
call para node
}
if n.nodetype=callparan then
begin
addstatement(statements,tcallparanode(n).left);
tcallparanode(n).left:=nodes;
do_firstpass(tcallparanode(n).left);
end
else
begin
addstatement(statements,n);
n:=nodes;
do_firstpass(n);
end;
{$ifdef csedebug}
printnode(output,nodes);
{$endif csedebug}
end;
end
end;
end;
function do_optcse(var rootnode : tnode) : tnode;
var
deletes,
statements : tstatementnode;
deleteblock,
rootblock : tblocknode;
begin
{$ifdef csedebug}
writeln('====================================================================================');
writeln('CSE optimization pass started');
writeln('====================================================================================');
printnode(rootnode);
writeln('====================================================================================');
writeln;
{$endif csedebug}
deleteblock:=internalstatements(deletes);
foreachnodestatic(pm_postprocess,rootnode,@searchcsedomain,@deletes);
rootblock:=internalstatements(statements);
addstatement(statements,rootnode);
addstatement(statements,deleteblock);
rootnode:=rootblock;
do_firstpass(rootnode);
{$ifdef csedebug}
writeln('====================================================================================');
writeln('CSE optimization result');
writeln('====================================================================================');
printnode(rootnode);
writeln('====================================================================================');
writeln;
{$endif csedebug}
result:=nil;
end;
end.
|