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Deal with a number of issues in some expressions.

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- Move TODO of <0 to !=-1 to boolean, as it's counter-productive otherwise.
- All a!=b except list!=list are equivalent to !(a==b).
- Change a>b to b<a to simplify cases to analize.
- Proper fall-through in some spots, or return in some others where it didn't apply.
- Simplify handling of a<-2147483648 as a&0, falling through, instead of coping with it ourselves.
This commit is contained in:
Sei Lisa 2015-03-28 20:23:47 +01:00
parent de33c2df01
commit c154d5eb0d
1 changed files with 28 additions and 22 deletions
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50
lslopt/lslfoldconst.py
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@ -146,6 +146,8 @@ class foldconst(object):
# expression of the form !(a&-b) (if b is bool).
# TODO: Convert bool(x < 0) to bool(x & 0x80000000)
# TODO: If function domain starts at -1, treat & 0x80000000 as ~
# TODO: If function domain starts at -1, treat < 0 as ~
def CopyNode(self, node):
@ -609,41 +611,45 @@ class foldconst(object):
return
return
if nt in ('<=', '>=') or nt == '!=' \
and child[0]['t'] in ('float', 'integer') \
and child[1]['t'] in ('float', 'integer'):
if nt in ('<=', '>=') or nt == '!=' and child[0]['t'] != 'list':
# Except for list != list, all these comparisons are compiled
# as !(a>b) etc. so we transform them here in order to reduce
# the number of cases to check.
# a<=b --> !(a>b); a>=b --> !(a<b); a!=b --> !(a==b)
SEF = 'SEF' in node
node['nt'] = {'<=':'>', '>=':'<', '!=':'=='}[nt]
node = parent[index] = {'nt':'!', 't':node['t'], 'ch':[node]}
if SEF:
node['SEF'] = True
# Fold the new node
self.FoldTree(parent, index)
return
# Fall through to optimize as '<' or '>' or '=='
if nt in ('<', '>'):
# TODO: If function domain is -1..INT_MAX, treat <0 as !=-1
if nt == '>':
# Invert the inequalities to avoid doubling the cases to check.
# a>b --> b<a
nt = node['nt'] = '<'
child[1], child[0] = child[0], child[1]
# fall through to check for '<'
# i>2147483647 to FALSE if SEF, otherwise convert to a&0
# i<-2147483648 to FALSE if SEF, otherwise convert to a&0
a, b = 0, 1
if child[a]['nt'] == 'CONST':
a,b = 1,0
if child[b]['nt'] == 'CONST' and child[a]['t'] == child[b]['t'] == 'integer' \
and (nt == '>' and child[b]['value'] == 2147483647
or nt == '<' and child[b]['value'] == -2147483648):
if 'SEF' in child[a]:
parent[index] = node = child[b]
node['value'] = 0
return
if nt == '<':
# Convert 2147483647<i and i<-2147483648 to i&0
if child[0]['t'] == child[1]['t'] == 'integer' \
and (child[0]['nt'] == 'CONST' and child[0]['value'] == 2147483647
or child[1]['nt'] == 'CONST' and child[1]['value'] == -2147483648):
a, b = 0, 1
# Put the constant in child[b]
if child[a]['nt'] == 'CONST':
a, b = 1, 0
nt = node['nt'] = '&'
child[b]['value'] = 0
# fall through to check for '&'
else:
return
if nt in ('&', '|'):
# Deal with operands in any order
a, b = 0, 1
if child[a]['nt'] == 'CONST' and child[a]['t'] in ('float', 'integer'):
# Put constant in child[b]
if child[b]['nt'] != 'CONST':
a, b = 1, 0
if child[b]['nt'] == 'CONST':
@ -658,7 +664,7 @@ class foldconst(object):
# a&0 -> 0 if a is SEF
if 'SEF' in child[a]:
parent[index] = child[b]
return
return
if nt == '^':
a, b = 0, 1