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Project-02-03-04/cfg_build.py

@@ -9,6 +9,13 @@ import compiler
 import syntax
 
 
+# -------------------------------------------------
+# Global function environment
+# -------------------------------------------------
+
+FUNCTIONS = {}  # name -> (func_start, func_end)
+
+
 # -------------------------------------------------
 # Expressions — NO CFG NODES
 # -------------------------------------------------
@@ -64,13 +71,21 @@ class SEQ(compiler.SEQ):
 
 class IF(compiler.IF):
     def cfa(self, pred, end):
-        cond = CFG_DIAMOND(self)
+        # decision node (condition only)
+        cond = CFG_DIAMOND(self.cond)
         pred.add_child(cond)
 
+        # explicit branch entries
+        then_entry = CFG_Node()
+        else_entry = CFG_Node()
+        cond.add_child(then_entry)
+        cond.add_child(else_entry)
+
+        # join node
         join = CFG_Node()
 
-        then_end = self.exp1.cfa(cond, end)
-        else_end = self.exp2.cfa(cond, end)
+        then_end = self.exp1.cfa(then_entry, end)
+        else_end = self.exp2.cfa(else_entry, end)
 
         if then_end is not None:
             then_end.add_child(join)
@@ -82,13 +97,19 @@ class IF(compiler.IF):
 
 class WHILE(compiler.WHILE):
     def cfa(self, pred, end):
-        cond = CFG_DIAMOND(self)
+        # loop condition
+        cond = CFG_DIAMOND(self.cond)
         pred.add_child(cond)
 
-        body_end = self.body.cfa(cond, end)
-        if body_end is not None:
-            body_end.add_child(cond)
+        # body entry
+        body_entry = CFG_Node()
+        cond.add_child(body_entry)
 
+        body_end = self.body.cfa(body_entry, end)
+        if body_end is not None:
+            body_end.add_child(cond)  # back-edge
+
+        # loop exit
         after = CFG_Node()
         cond.add_child(after)
 
@@ -96,21 +117,47 @@ class WHILE(compiler.WHILE):
 
 
 # -------------------------------------------------
-# Functions / calls
+# Functions / calls (interprocedural CFG)
 # -------------------------------------------------
 
 class CALL(compiler.CALL):
     def cfa(self, pred, end):
-        n = CFG_CALL(self)
-        pred.add_child(n)
-        return n
+        call = CFG_CALL(self)
+        pred.add_child(call)
+
+        # continuation after return
+        cont = CFG_Node()
+
+        if self.f_name not in FUNCTIONS:
+            raise RuntimeError(f"Call to undefined function '{self.f_name}'")
+
+        f_start, f_end = FUNCTIONS[self.f_name]
+
+        # call → function entry
+        call.add_child(f_start)
+
+        # function exit → continuation
+        f_end.add_child(cont)
+
+        return cont
 
 
 class DECL(compiler.DECL):
     def cfa(self, pred, end):
-        entry = CFG_Node(self)
-        pred.add_child(entry)
-        return self.body.cfa(entry, end)
+        # function entry / exit
+        f_start = CFG_Node(self)
+        f_end = CFG_Node(self)
+
+        # register function
+        FUNCTIONS[self.f_name] = (f_start, f_end)
+
+        # build function body
+        body_end = self.body.cfa(f_start, f_end)
+        if body_end is not None:
+            body_end.add_child(f_end)
+
+        # function declaration does not alter current control flow
+        return pred
 
 
 class LET(compiler.LET):
@@ -130,5 +177,5 @@ class RETURN(syntax.EXPRESSION):
     def cfa(self, pred, end):
         n = CFG_RETURN(self)
         pred.add_child(n)
-        n.add_child(end)   # direct jump to global END
+        n.add_child(end)   # return to function exit
         return None        # no fallthrough