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+ optimize '0 shl x' and '0 shr x' to 0

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git-svn-id: trunk@36041 -
This commit is contained in:
nickysn 2017-05-01 18:16:38 +00:00
parent 546e993c25
commit de1e0c405e
1 changed files with 22 additions and 0 deletions
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22
compiler/nmat.pas
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@ -702,6 +702,28 @@ implementation
result:=left;
left:=nil;
end;
end
else if is_constintnode(left) then
begin
lvalue:=tordconstnode(left).value;
{ shl/shr are unsigned operations, so cut off upper bits }
case resultdef.size of
1:
lvalue:=tordconstnode(left).value and byte($ff);
2:
lvalue:=tordconstnode(left).value and word($ffff);
4:
lvalue:=tordconstnode(left).value and dword($ffffffff);
8:
lvalue:=tordconstnode(left).value and qword($ffffffffffffffff);
else
internalerror(2013122301);
end;
{ '0 shl x' and '0 shr x' are 0 }
if (lvalue=0) and
((cs_opt_level4 in current_settings.optimizerswitches) or
not might_have_sideeffects(right)) then
result:=cordconstnode.create(0,resultdef,true);
end;
end;