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* try to transform the tree to be able to do better cse

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git-svn-id: trunk@21986 -
This commit is contained in:
florian 2012-07-29 21:29:07 +00:00
parent a27cc3e5f2
commit 562a45f2e1
1 changed files with 48 additions and 2 deletions
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50
compiler/optcse.pas
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@ -221,14 +221,60 @@ unit optcse;
statements : tstatementnode;
hp : ttempcreatenode;
addrstored : boolean;
hp2 : tnode;
begin
result:=fen_false;
if n.nodetype in cseinvariant then
begin
csedomain:=true;
foreachnodestatic(pm_postprocess,n,@searchsubdomain,@csedomain);
{ found a cse domain }
if csedomain then
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]) then
while n.nodetype=tbinarynode(n).left.nodetype 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;