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* never alias/coalesce cpu registers that are not usable by the register

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allocator (such as stack/framepointers) with virtual registers, otherwise
    they can get changed in case the virtual register gets changed (read-only
    use would be ok, but we don't keep track of which virtual registers are
    only read

git-svn-id: trunk@27104 -
This commit is contained in:
Jonas Maebe 2014-03-11 23:18:45 +00:00
parent c88cebfc97
commit 246caf3526
1 changed files with 18 additions and 3 deletions
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21
compiler/rgobj.pas
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@ -1121,6 +1121,15 @@ unit rgobj;
procedure trgobj.set_alias(u,v:Tsuperregister);
begin
{ don't make registers that the register allocator shouldn't touch (such
as stack and frame pointers) be aliases for other registers, because
then it can propagate them and even start changing them if the aliased
register gets changed }
if ((u<first_imaginary) and
not(u in usable_register_set)) or
((v<first_imaginary) and
not(v in usable_register_set)) then
exit;
include(reginfo[v].flags,ri_coalesced);
if reginfo[v].alias<>0 then
internalerror(200712291);
@ -1272,9 +1281,15 @@ unit rgobj;
add_worklist(u);
add_worklist(v);
end
{Next test: is it possible and a good idea to coalesce??}
else if ((u<first_imaginary) and adjacent_ok(u,v)) or
conservative(u,v) then
{Next test: is it possible and a good idea to coalesce?? Note: don't
coalesce registers that should not be touched by the register allocator,
such as stack/framepointers, because otherwise they can be changed }
else if (((u<first_imaginary) and adjacent_ok(u,v)) or
conservative(u,v)) and
((u>first_imaginary) or
(u in usable_register_set)) and
((v>first_imaginary) or
(v in usable_register_set)) then
begin
m.moveset:=ms_coalesced_moves; {Move coalesced!}
coalesced_moves.insert(m);