Added basic block recognizer.

src/basic_block.py

+# TODO: Get all jump commands
+JUMP_COMMANDS = ['j', 'jal']
+
+def is_jump(line):
+    '''Check if a statement is a jump command.'''
+    return line[0] == 'command' and line[1] in JUMP_COMMANDS
+
+def find_leaders(lines):
+    '''Determine the leaders, which are:
+       1. The first statement.
+       2. Any statement that is the target of a jump.
+       3. Any statement that follows directly follows a jump.'''
+    leaders = [0]
+    jump_target_labels = []
+
+    # Append statements following jumps and save jump target labels
+    for i, line in enumerate(lines[1:]):
+        if is_jump(line):
+            leaders.append(i + 2)
+            jump_target_labels.append(line[2]['args'][0])
+            #print 'found jump:', i, line
+
+    #print 'target labels:', jump_target_labels
+
+    # Append jump targets
+    for i, line in enumerate(lines[1:]):
+        if i + 1 not in leaders \
+                and line[0] == 'label' \
+                and line[1] in jump_target_labels:
+            leaders.append(i + 1)
+            #print 'target:', i + 1, lines[i + 1]
+
+    return leaders
+
+def find_basic_blocks(lines):
+    '''Divide a statement list into basic blocks. Returns a list of basic
+    blocks, which are also statement lists.'''
+    leaders = find_leaders(lines)
+    blocks = []
+
+    for i in range(len(leaders) - 1):
+        blocks.append(lines[leaders[i]:leaders[i + 1]])
+
+    return blocks

src/optimize.py

+#!/usr/bin/python
+from parser import parse_file
+from basic_block import find_basic_blocks
+
+if __name__ == '__main__':
+    from sys import argv, exit
+
+    if len(argv) < 2:
+        print 'Usage: python %s FILE' % argv[0]
+        exit(1)
+
+    lines = parse_file(argv[1])
+    blocks = find_basic_blocks(lines)
+
+    #for i, line in enumerate(lines):
+    #    print i, line
+
+    for i, block in enumerate(blocks):
+        print '\nbasic block %d:' % i
+
+        for line in block:
+            print line