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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 -
This commit is contained in:
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;
{ slow simplifications }
if (cs_opt_level2 in current_settings.optimizerswitches) then
if cs_opt_level2 in current_settings.optimizerswitches then
begin
{ the comparison is might be expensive and the nodes are usually only
equal if some previous optimizations were done so don't check
this simplification always
}
if is_boolean(left.resultdef) and is_boolean(right.resultdef) and
{ 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
if is_boolean(left.resultdef) and is_boolean(right.resultdef) then
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
case nodetype of
andn,orn:
@ -940,8 +940,25 @@ implementation
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
memory accesses while sqr(<real>) has no drawback }