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@@ -33,88 +33,55 @@ def eliminate_common_subexpressions(block):
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occurrences to a move instruction from that address.
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"""
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changed = False
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- prev = False
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block.reset()
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while not block.end():
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s = block.read()
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- args = s[1:]
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- mult = False
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-
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- if s.is_command('mflo') and prev and prev.name == 'mult':
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- mult = prev
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- args = mult.args
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- elif not s.is_arith():
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- prev = s
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- continue
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-
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- pointer = block.pointer
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- occurrences = [pointer - 1]
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- # Collect similar statements
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- while not block.end():
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- s2 = block.read()
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+ if s.is_arith():
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+ pointer = block.pointer
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+ occurrences = [pointer - 1]
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+ args = s[1:]
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- if not s2.is_command():
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- continue
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+ # Collect similar statements
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+ while not block.end():
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+ s2 = block.read()
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- # Stop if one of the arguments is assigned
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- assign = False
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+ if not s2.is_command():
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+ continue
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- for reg in s2.get_def():
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- if reg in args:
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- assign = True
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+ # Stop if one of the arguments is assigned
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+ if len(s2) and s2[0] in args:
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break
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- if assign:
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- break
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-
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- # Replace a similar expression by a move instruction
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- if mult:
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- # Multiplication has two instructions: mult and mflo
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- if s2.name == 'mult' and s2.args == args:
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- mflo = block.peek()
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-
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- if mflo.is_command('mflo'):
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- occurrences.append(block.pointer - 1)
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- elif s2.name == s.name and s2[1:] == args:
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- # Regular arithmetic command
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- occurrences.append(block.pointer - 1)
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-
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- if len(occurrences) > 1:
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- new_reg = find_free_reg(block, occurrences[0])
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-
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- # Replace each occurrence with a move statement
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- message = 'Common subexpression reference: %s %s' \
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- % (s.name, ','.join(map(str, [new_reg] + s[1:])))
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-
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- for occurrence in occurrences:
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- rd = block[occurrence][0]
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- block.replace(1, [S('command', 'move', rd, new_reg)], \
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- start=occurrence, message=message)
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-
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- # Insert the calculation before the original with the new
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- # destination address
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- if mult:
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- message = 'Common subexpression: mult ' \
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- + ','.join(map(str, args))
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- block.insert(S('command', 'mult', *args), \
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- index=occurrences[0], message=message)
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- block.insert(S('command', 'mflo', new_reg), \
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- index=occurrences[0], message=' |')
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- else:
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+ # Replace a similar expression by a move instruction
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+ if s2.name == s.name and s2[1:] == args:
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+ occurrences.append(block.pointer - 1)
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+
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+ if len(occurrences) > 1:
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+ new_reg = find_free_reg(block, occurrences[0])
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+
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+ # Replace each occurrence with a move statement
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+ message = 'Common subexpression reference: %s %s' \
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+ % (s.name, ','.join(map(str, [new_reg] + s[1:])))
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+
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+ for occurrence in occurrences:
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+ rd = block[occurrence][0]
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+ block.replace(1, [S('command', 'move', rd, new_reg)], \
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+ start=occurrence, message=message)
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+
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+ # Insert the calculation before the original with the new
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+ # destination address
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message = 'Common subexpression: %s %s' \
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% (s.name, ','.join(map(str, s)))
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block.insert(S('command', s.name, *([new_reg] + args)), \
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index=occurrences[0], message=message)
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- changed = True
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-
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- prev = s
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+ changed = True
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- # Reset pointer to continue from the original statement
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- block.pointer = pointer
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+ # Reset pointer to continue from the original statement
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+ block.pointer = pointer
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return changed
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@@ -489,7 +456,6 @@ def propagate_copies(block):
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# definition reaching it -> s in in[B_use]
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if s.sid in block.reach_out:
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for b in filter(lambda b: (x, y) in b.copy_in, succ(block)):
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- print b
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for s2 in b:
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# Determine if for each of those uses this is the only
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# definition reaching it -> s in in[B_use]
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Taddeus Kroes