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* if a for loop does not change a variable, we can propate it if it is a constant, resolves #39726

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florian 2022-05-20 22:50:59 +02:00
parent 8817e896db
commit a1ee4e04ed
2 changed files with 30 additions and 2 deletions
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26
compiler/optconstprop.pas
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@ -55,9 +55,11 @@ unit optconstprop;
implementation
uses
globtype,
pass_1,procinfo,compinnr,
symsym, symconst,
nutils, nbas, ncnv, nld, nflw, ncal, ninl;
nutils, nbas, ncnv, nld, nflw, ncal, ninl,
optbase, optutils;
function check_written(var n: tnode; arg: pointer): foreachnoderesult;
begin
@ -71,7 +73,8 @@ unit optconstprop;
end;
{ propagates the constant assignment passed in arg into n }
{ propagates the constant assignment passed in arg into n, it returns true if
the search can continue with the next statement }
function replaceBasicAssign(var n: tnode; arg: tnode; var tree_modified: boolean): boolean;
var
st2, oldnode: tnode;
@ -131,6 +134,20 @@ unit optconstprop;
if result then
replaceBasicAssign(tfornode(n).t1, arg, tree_modified2);
tree_modified:=tree_modified or tree_modified2;
if pi_dfaavailable in current_procinfo.flags then
begin
CalcDefSum(tfornode(n).t2);
{ the constant can propagete if is is not the counter variable ... }
if not(tassignmentnode(arg).left.isequal(tfornode(n).left)) and
{ if it is a temprefn or its address is not taken in case of loadn }
((tassignmentnode(arg).left.nodetype=temprefn) or not(tabstractvarsym(tloadnode(tassignmentnode(arg).left).symtableentry).addr_taken)) and
{ and no definition in the loop? }
not(DFASetIn(tfornode(n).t2.optinfo^.defsum,tassignmentnode(arg).left.optinfo^.index)) then
begin
replaceBasicAssign(tfornode(n).t2, arg, tree_modified3);
tree_modified:=tree_modified or tree_modified3;
end;
end;
{ after a for node we cannot continue with our simple approach }
result:=false;
end
@ -317,6 +334,11 @@ unit optconstprop;
is_constenumnode(a.right) or
is_conststringnode(a.right)) then
begin
{$ifdef DEBUG_CONSTPROP}
writeln('******************************* propagating ***********************************');
printnode(a);
writeln('*******************************************************************************');
{$endif DEBUG_CONSTPROP}
st2:=tstatementnode(tstatementnode(st).right);
old:=@tstatementnode(st).right;
while assigned(st2) do

6
compiler/psub.pas
View File

@ -1221,6 +1221,12 @@ implementation
include(flags,pi_dfaavailable);
RedoDFA:=false;
if cs_opt_constant_propagate in current_settings.optimizerswitches then
do_optconstpropagate(code);
if RedoDFA then
dfabuilder.redodfainfo(code);
if (cs_opt_loopstrength in current_settings.optimizerswitches)
{ our induction variable strength reduction doesn't like
for loops with more than one entry }