Implement basic if statement rendering in LLVM IR

- Add _emit_if() method to handle if statements
- Add _emit_expr() to evaluate signal references and constants
- Create basic blocks for then/else/merge
- Convert condition to i1 and branch
- Test passing: test_if_statement_codegen

ritz/llvm_codegen_signals.py

@@ -188,8 +188,69 @@ class SignalLLVMIRGenerator:
             return self._emit_with(stmt)
         elif stmt["type"] == "yield":
             return self._emit_yield(stmt)
+        elif stmt["type"] == "if":
+            return self._emit_if(stmt)
         return None
 
+    def _emit_if(self, stmt: dict[str, Any]) -> str | None:
+        """Emit an if statement."""
+        # Generate unique labels for this if statement
+        if_id = self._new_var()
+        then_label = f"if.then.{if_id}"
+        else_label = f"if.else.{if_id}"
+        end_label = f"if.end.{if_id}"
+
+        # Evaluate condition
+        test_var = self._emit_expr(stmt["test"])
+
+        # Convert to i1 (boolean)
+        cond_var = self._new_var()
+        self.lines.append(f"  %{cond_var} = icmp ne i32 %{test_var}, 0")
+
+        # Branch based on whether there's an else
+        has_else = stmt.get("orelse") and len(stmt["orelse"]) > 0
+        if has_else:
+            self.lines.append(f"  br i1 %{cond_var}, label %{then_label}, label %{else_label}")
+        else:
+            self.lines.append(f"  br i1 %{cond_var}, label %{then_label}, label %{end_label}")
+
+        # Emit then block
+        self.lines.append(f"{then_label}:")
+        for then_stmt in stmt["body"]:
+            self._emit_statement(then_stmt)
+        self.lines.append(f"  br label %{end_label}")
+
+        # Emit else block if present
+        if has_else:
+            self.lines.append(f"{else_label}:")
+            for else_stmt in stmt["orelse"]:
+                self._emit_statement(else_stmt)
+            self.lines.append(f"  br label %{end_label}")
+
+        # Emit merge block
+        self.lines.append(f"{end_label}:")
+
+        return None
+
+    def _emit_expr(self, expr: dict[str, Any]) -> str:
+        """Emit an expression and return the result variable name."""
+        if expr["type"] == "name":
+            # Load signal value
+            signal_name = expr["id"]
+            if signal_name in self.signals:
+                load_var = self._new_var()
+                self.lines.append(f"  %{load_var} = load i32, i32* @signal_{signal_name}")
+                return load_var
+            else:
+                # Unknown variable
+                return "0"
+        elif expr["type"] == "constant":
+            # Return constant inline
+            return str(expr["value"])
+        else:
+            # Unknown expression type
+            return "0"
+
     def _emit_with(self, stmt: dict[str, Any]) -> str:
         """Emit a 'with Element()' block."""
         element_info = stmt["element"]