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* short boolean evaluation is too expensive for simple nodes with no side effects, do full evaluation in this case

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git-svn-id: trunk@35229 -
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florian 2017-01-04 16:33:27 +00:00
parent 233185a4e5
commit 3e2aff15fb
1 changed files with 28 additions and 11 deletions
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39
compiler/nadd.pas
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@ -909,21 +909,21 @@ implementation
end; end;
{ slow simplifications } { slow simplifications }
if (cs_opt_level2 in current_settings.optimizerswitches) then if cs_opt_level2 in current_settings.optimizerswitches then
begin begin
{ the comparison is might be expensive and the nodes are usually only { the comparison is might be expensive and the nodes are usually only
equal if some previous optimizations were done so don't check equal if some previous optimizations were done so don't check
this simplification always this simplification always
} }
if is_boolean(left.resultdef) and is_boolean(right.resultdef) and if is_boolean(left.resultdef) and is_boolean(right.resultdef) then
{ even when short circuit boolean evaluation is active, this
optimization cannot be performed in case the node has
side effects, because this can change the result (e.g., in an
or-node that calls the same function twice and first returns
false and then true because of a global state change }
not might_have_sideeffects(left) then
begin begin
if left.isequal(right) then { even when short circuit boolean evaluation is active, this
optimization cannot be performed in case the node has
side effects, because this can change the result (e.g., in an
or-node that calls the same function twice and first returns
false and then true because of a global state change }
if not might_have_sideeffects(left) and
left.isequal(right) then
begin begin
case nodetype of case nodetype of
andn,orn: andn,orn:
@ -940,8 +940,25 @@ implementation
end; end;
} }
end; end;
end; end
end; { short to full boolean evalution possible and useful? }
else if not(might_have_sideeffects(right)) and not(cs_full_boolean_eval in localswitches) then
begin
case nodetype of
andn,orn:
{ full boolean evaluation is only useful if the nodes are not too complex and if no flags/jumps must be converted,
further, we need to know the expectloc }
if (node_complexity(right)<=2) and
not(left.expectloc in [LOC_FLAGS,LOC_JUMP,LOC_INVALID]) and not(right.expectloc in [LOC_FLAGS,LOC_JUMP,LOC_INVALID]) then
begin
{ we need to copy the whole tree to force another pass_1 }
include(localswitches,cs_full_boolean_eval);
result:=getcopy;
exit;
end;
end;
end
end;
{ using sqr(x) for reals instead of x*x might reduces register pressure and/or { using sqr(x) for reals instead of x*x might reduces register pressure and/or
memory accesses while sqr(<real>) has no drawback } memory accesses while sqr(<real>) has no drawback }