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Optimize comparisons of the form int>2147483647 or int<-2147483648 and expand (>=, <=, !=) to !(<, >, ==) respectively.

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Sei Lisa 2015-03-03 02:16:00 +01:00
parent 493aed6c39
commit 05d46e9ac3
1 changed files with 30 additions and 7 deletions
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37
lslopt/lslfoldconst.py
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@ -191,6 +191,8 @@ class foldconst(object):
if subexpr['nt'] == 'CONST': if subexpr['nt'] == 'CONST':
node = parent[index] = subexpr node = parent[index] = subexpr
node['value'] = int(not node['value']) node['value'] = int(not node['value'])
# TODO: Missing comparison optimization
# !(i>const) to i<(const+1) if no overflow (4 variants)
return return
if nt == '~': if nt == '~':
@ -543,8 +545,8 @@ class foldconst(object):
# expr * 1 -> expr # expr * 1 -> expr
# expr * 0 -> 0 if side-effect free # expr * 0 -> 0 if side-effect free
# expr * -1 -> -expr # expr * -1 -> -expr
# ident * 2 -> ident + ident (no gain except if ident is local) # ident * 2 -> ident + ident (only if ident is local)
# ident * -2 -> -(ident + ident) (this is counter-productive if ident is not local) # ident * -2 -> -(ident + ident) (only if ident is local)
# expr/1 -> expr # expr/1 -> expr
# expr/-1 -> -expr # expr/-1 -> -expr
if nt == '*' and child[b]['t'] in ('float', 'integer') \ if nt == '*' and child[b]['t'] in ('float', 'integer') \
@ -574,13 +576,34 @@ class foldconst(object):
return return
return return
# TODO: Missing comparison optimization if nt in ('<=', '>=') or nt == '!=' \
# (a<=b) to !(a>b) and child[0]['t'] in ('float', 'integer') \
# (a>=b) to !(a<b) and child[1]['t'] in ('float', 'integer'):
# (a!=b) to !(a==b) SEF = 'SEF' in node
# !(i>const) to i<(const+1) if no overflow (4 variants) node['nt'] = {'<=':'>', '>=':'<', '!=':'=='}[nt]
node = parent[index] = {'nt':'NEG', 't':node['t'], 'ch':[node]}
if SEF:
node['SEF'] = True
# Fold the new node
self.FoldTree(parent, index)
return
if nt in ('<', '>'):
# i>2147483647 to FALSE if SEF, otherwise convert to a&0 # i>2147483647 to FALSE if SEF, otherwise convert to a&0
# i<-2147483648 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
nt = node['nt'] = '&'
child[b]['value'] = 0
# fall through to check for '&'
if nt in ('&', '|'): if nt in ('&', '|'):
# Deal with operands in any order # Deal with operands in any order