Fix some bugs in if handling, add support for ternary ?:

1 files changed, 51 insertions, 7 deletions

diff --git a/pp2cc.py b/pp2cc.py
index 30dc5e0..3ae5c0a 100755
--- a/pp2cc.py
+++ b/pp2cc.py
@@ -10,7 +10,7 @@ permission. The generated output (assembly and messages) are not subject to
 this license.
 """
 
-import sys
+import sys, re
 from pycparser import c_parser, c_ast
 
 __author__ = "Peter Wu"
@@ -123,6 +123,10 @@ class Asm(object):
         indent_size = len(instruction) - len(new_instruction)
         return self.format_line(new_instruction, label, indent_size)
 
+    def has_label(self, line):
+        """"Returns True if a line appears to contain a label, False otherwise"""
+        return Parse.is_identifier(line.split(":", 1)[0].strip())
+
     def noop(self, label, register="R0"):
         """Returns a labelled no operation operator
         
@@ -182,6 +186,10 @@ class Logger(object):
         print type + ":" + source + message
 
 class Parse(object):
+    re_identifier = re.compile("^[0-9a-zA-Z_][0-9a-zA-Z_]*$")
+    @classmethod
+    def is_identifier(cls, text):
+        return cls.re_identifier.match(text)
     def __init__(self, filename, source=''):
         if source is "":
             file = open(filename, 'r')
@@ -547,6 +555,42 @@ class Parse(object):
         else:
             raise RuntimeError("Unknown unary operator '{}'".format(op))
         return lines
+    def parseTernaryOp(self, linked_node):
+        """Returns lines of ASM for ternary operation cond?expr_true:expr_false
+        
+        It looks very similar to an If expect that the return value is important
+        """
+        linked_node.incrementLevel()
+        node = linked_node.node
+        lbl_el = self.uniqLbl("el") # else
+        lbl_end = self.uniqLbl("fi") # endif
+        
+        lines = self.parseStatement(node.cond, linked_node)
+        lines.append(self.asm.branch_op("BEQ", lbl_el))
+
+        # if true...
+        then_block = self.parseStatement(node.iftrue, linked_node)
+        # use a single register for the result, using the one of expr_true
+        result_reg = self.registers.find_register(then_block, fatal=True)
+        lines += then_block
+        lines.append(self.asm.branch_op("BRA", lbl_end))
+
+        # else...
+        else_block = self.parseStatement(node.iffalse, linked_node)
+        assert len(else_block), "Else block is empty"
+        result_reg_else = self.registers.find_register(else_block, fatal=True)
+        # for consistency with the result of expr_true
+        if result_reg_else != result_reg:
+            lines.append(self.asm.binary_op("LOAD", result_reg, result_reg_else))
+        # add labels for the else block
+        if self.asm.has_label(else_block[0]):
+            lines.append(self.asm.noop(lbl_el))
+        else:
+            else_block[0] = self.asm.insert_label(else_block[0], lbl_el)
+        lines += else_block
+
+        lines.append(self.asm.noop(lbl_end, register=result_reg))
+        return lines
     def convertInteger(self, value=None, node=None):
         if value is None:
             if isinstance(node, c_ast.Constant) and node.type == "int":
@@ -595,7 +639,8 @@ class Parse(object):
         #lbl_if = self.uniqLbl("if") # if
         #lbl_th = self.uniqLbl("th") # then
         if node.iffalse:
-            lbl_end = lbl_el = self.uniqLbl("el") # else
+            lbl_el = self.uniqLbl("el") # else
+            lbl_end = self.uniqLbl("fi") # endif
         else:
             lbl_end = lbl_fi = self.uniqLbl("fi") # endif
 
@@ -607,7 +652,7 @@ class Parse(object):
         #        lines[0] = self.asm.insert_label(lines[0], lbl_if)
 
         # if cond is zero, go to else (BEQ branches if Z=0). Do not use CMP
-        lines.append(self.asm.branch_op("BEQ", lbl_end))
+        lines.append(self.asm.branch_op("BEQ", lbl_el))
 
         # if true...
         then_block = self.parseStatement(node.iftrue, linked_node)
@@ -627,7 +672,7 @@ class Parse(object):
                 if self.asm.has_label(else_block[0]):
                     lines.append(self.asm.noop(lbl_el))
                 else:
-                    else_block[0] = self.asm.insert_label(else_block, lbl_el)
+                    else_block[0] = self.asm.insert_label(else_block[0], lbl_el)
             lines += else_block
             # why branch if already at the end of the block? hmm
             #lines.append(self.asm.branch_op("BRA", lbl_end))
@@ -682,13 +727,12 @@ class Parse(object):
             raise RuntimeError("Not implemented for type " + repr(node))
         elif isinstance(node, c_ast.PtrDecl):
             raise RuntimeError("Not implemented for type " + repr(node))
-        elif isinstance(node, c_ast.TernaryOp):
-            raise RuntimeError("Not implemented for type " + repr(node))
         elif isinstance(node, c_ast.While):
             raise RuntimeError("Not implemented for type " + repr(node))
         else:
             for entry in ("Compound", "BinaryOp", "If", "Constant", "ID",
-                          "Return", "FuncCall", "UnaryOp", "Cast"):
+                          "Return", "FuncCall", "UnaryOp", "Cast",
+                          "TernaryOp"):
                 if isinstance(node, getattr(c_ast, entry)):
                     lines += getattr(self, "parse" + entry)(linked_node)
                     break