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Optimize 'if' statements better.

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if (!cond) X; else Y;  ->  if (cond) Y; else X;

if (int1 == int2) X; else Y;  ->  if (int1 ^ int2) Y; else X;

When 'cond' is of a type other than 'key': if (cond) ; else X;  ->  if (!cond) X;  (this required changing if(str) to its compiled equivalent if(!(str == "")), so that 'cond' is always either key or integer).

if (cond) ;  ->  cond; and folds it as a statement, which may eliminate it if it's SEF. This is done after eliminating 'else ;' so that it also optimizes 'if (cond) ; else ;' the same way.

This removes a TODO item.
This commit is contained in:
Sei Lisa 2017-10-30 18:45:56 +01:00
parent ed49170d87
commit 097c054494
1 changed files with 40 additions and 2 deletions
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42
lslopt/lslfoldconst.py
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@ -226,12 +226,15 @@ class foldconst(object):
ctyp = parent[index]['t']
# Under LSO, this would break the fact that 1-element lists count as
# false, so we don't do it for LSO lists.
if ctyp in ('float', 'vector', 'rotation') or ctyp == 'list' and not lslcommon.LSO:
if (ctyp in ('float', 'vector', 'rotation', 'string')
or ctyp == 'list' and not lslcommon.LSO
):
parent[index] = {'nt':'!=', 't':'integer', 'ch':[parent[index],
{'nt':'CONST', 't':ctyp, 'value':
0.0 if ctyp == 'float'
else ZERO_VECTOR if ctyp == 'vector'
else ZERO_ROTATION if ctyp == 'rotation'
else u"" if ctyp == 'string'
else []}]}
parent[index]['SEF'] = 'SEF' in parent[index]['ch'][0]
@ -1573,7 +1576,6 @@ class foldconst(object):
return
if nt == 'IF':
# TODO: Swap IF/ELSE if both present and cond starts with !
self.ExpandCondition(child, 0)
self.FoldTree(child, 0)
self.FoldCond(child, 0)
@ -1630,9 +1632,45 @@ class foldconst(object):
if len(child) > 2:
self.FoldTree(child, 2)
self.FoldStmt(child, 2)
if self.DoesSomething(child[2]):
# Check if we can gain something by negating the
# expression.
# Swap 'if' and 'else' branch when the condition has
# a '!' prefix
if child[0]['nt'] == '!':
child[0] = child[0]['ch'][0]
child[1], child[2] = child[2], child[1]
# Swap them if condition is '==' with integer operands
if (child[0]['nt'] == '=='
and child[0]['ch'][0]['t']
== child[0]['ch'][1]['t'] == 'integer'
):
child[0]['nt'] = '^'
child[1], child[2] = child[2], child[1]
# Re-test just in case we swapped in the previous check.
if not self.DoesSomething(child[2]):
# no point in "... else ;" - remove else branch
del child[2]
if not self.DoesSomething(child[1]):
# if (X) ; -> X;
if len(child) == 2:
parent[index] = child[0]
# It has been promoted to statement. Fold it.
# (Will remove it if SEF)
self.FoldStmt(child, 0)
return
# If type(X) != Key, then:
# if (X) ; else {stuff} -> if (!X) {stuff}
if child[0]['t'] != 'key':
# We've already converted all other types to equivalent
# comparisons
assert child[0]['t'] == 'integer'
child[0] = {'nt':'!', 't':'integer', 'ch':[child[0]]}
del child[1]
self.FoldTree(child, 0)
self.FoldCond(child, 0)
if all('SEF' in subnode for subnode in child):
node['SEF'] = True
return