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Simplify const + nonconst + const and nonconst + const + const.

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Sei Lisa 2014-08-19 19:45:47 +02:00
parent c2437b33e7
commit c2a30fb9ee
1 changed files with 26 additions and 4 deletions
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30
lslopt/lslfoldconst.py
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@ -153,9 +153,10 @@ class foldconst(object):
# Child is an unary postfix expression (highest priority); # Child is an unary postfix expression (highest priority);
# parentheses are redundant and can be removed safely. Not # parentheses are redundant and can be removed safely. Not
# strictly an optimization but it helps keeping the output # strictly an optimization but it helps keeping the output
# tidy-ish a bit. It's not done in general (e.g. (a * b) + c # tidy-ish a bit, and helps the optimizer do its work. It's not
# does not need parentheses but these are not eliminated). Only # done in general (e.g. (a * b) + c does not need parentheses
# cases like (3) or (myvar++) are simplified. # but these are not eliminated). Only cases like (3) or
# (myvar++) are simplified.
parent[index] = child[0] parent[index] = child[0]
return return
@ -244,6 +245,14 @@ class foldconst(object):
if nt == '+': if nt == '+':
# Tough one. Remove neutral elements for the diverse types, # Tough one. Remove neutral elements for the diverse types,
# and more. # and more.
# Remove redundant parentheses
if lnt == '()' and lval['ch'][0]['nt'] in ('+', '-', '*', '/', '%'):
# (a op b) + c -> a op b + c
# where op's priority is that of + or greater
lval = child[0] = lval['ch'][0]
lnt = '+'
if optype == 'list' and not (ltype == rtype == 'list'): if optype == 'list' and not (ltype == rtype == 'list'):
if lnt == 'CONST' and not lval['value']: if lnt == 'CONST' and not lval['value']:
# [] + nonlist -> (list)nonlist # [] + nonlist -> (list)nonlist
@ -329,6 +338,19 @@ class foldconst(object):
return return
if lnt == '+' and (lval['ch'][0]['nt'] == 'CONST'
or rval['ch'][0]['nt'] == 'CONST'):
# We have var + const + const or const + var + const.
# Addition of integers mod 2^32 is associative and
# commutative, so constants can be merged.
if lval['ch'][0]['nt'] == 'CONST':
rval['value'] = lslfuncs.S32(rval['value'] + lval['ch'][0]['value'])
lval = child[0] = lval['ch'][1]
else:
rval['value'] = lslfuncs.S32(rval['value'] + lval['ch'][1]['value'])
lval = child[0] = lval['ch'][0]
lnt = lval['nt']
if rnt == 'CONST': if rnt == 'CONST':
# Swap the vars to deal with const in lval always # Swap the vars to deal with const in lval always
lval, lnt, rval, rnt = rval, rnt, lval, lnt lval, lnt, rval, rnt = rval, rnt, lval, lnt
@ -400,7 +422,7 @@ class foldconst(object):
return return
elif nt == '<<' and child[1]['nt'] == 'CONST': if nt == '<<' and child[1]['nt'] == 'CONST':
# Transforming << into multiply saves some bytes. # Transforming << into multiply saves some bytes.
if child[1]['value'] & 31: if child[1]['value'] & 31:
# x << 3 --> x * 8 # x << 3 --> x * 8