Merge pull request #23 from feat/deadcode

Feat(optimizer): Otimização de eliminação de deadcode após return

Author: Sophiassilva

src/ast.c

@@ -37,7 +37,7 @@ static void ensure_capacity(void **buffer, size_t elem_size, size_t *capacity, s
 }
 
 static void ast_expr_destroy(AstExpr *expr);
-static void ast_stmt_destroy(AstStmt *stmt);
+void ast_stmt_destroy(AstStmt *stmt);
 
 AstProgram *ast_program_create(void)
 {
@@ -229,7 +229,7 @@ void ast_stmt_list_destroy(AstStmtList *list)
 	list->capacity = 0;
 }
 
-static void ast_stmt_destroy(AstStmt *stmt)
+void ast_stmt_destroy(AstStmt *stmt)
 {
 	if (!stmt)
 	{

src/ast.h

@@ -223,6 +223,7 @@ void ast_expr_list_destroy(AstExprList *list);
 AstStmtList ast_stmt_list_make(void);
 void ast_stmt_list_push(AstStmtList *list, AstStmt *stmt);
 void ast_stmt_list_destroy(AstStmtList *list);
+void ast_stmt_destroy(AstStmt *stmt);
 
 AstBlock ast_block_from_list(AstStmtList *list);
 

src/optimizer.c

@@ -51,6 +51,7 @@ static char *dup_string(const char *value);
 static void *xmalloc(size_t size);
 static int compare_entries_by_index(const void *lhs, const void *rhs);
 static int occurrence_survives_dce(const CseOccurrence *occ);
+static void eliminate_unreachable(AstStmtList *list);
 
 void optimize_program(AstProgram *program)
 {
@@ -89,6 +90,7 @@ static void optimize_block(AstBlock *block)
 	{
 		optimize_statement_children(block->statements.items[i]);
 	}
+	eliminate_unreachable(&block->statements);
 }
 
 static void optimize_statement_children(AstStmt *stmt)
@@ -608,3 +610,29 @@ static char *expr_make_key(const AstExpr *expr)
 		return dup_string("<unsupported>");
 	}
 }
+
+static void eliminate_unreachable(AstStmtList *list)
+{
+	if (!list)
+		return;
+
+	int after_return = 0;
+	size_t write = 0;
+
+	for (size_t i = 0; i < list->count; i++)
+	{
+		AstStmt *s = list->items[i];
+		if (after_return)
+		{
+			ast_stmt_destroy(s);
+			continue;
+		}
+		list->items[write++] = s;
+		if (s->kind == STMT_RETURN)
+		{
+			after_return = 1;
+		}
+	}
+
+	list->count = write;
+}

tests/pass/deadcode.c

@@ -0,0 +1,6 @@
+int main()
+{
+    int a = 10;
+    return a;
+    int b = 20;
+}

tests/pass/deadcode.lua

@@ -0,0 +1,4 @@
+os.exit((function(args)
+	local a = 10
+	return a
+end)(arg))

tests/pass/expressions.c

@@ -18,5 +18,5 @@ int main(int K)
     int a = 10;
     int b = 20;
     int r = sum(a, b) + add(a, b);
-    return 0;
+    return r;
 }

tests/pass/expressions.lua

@@ -13,5 +13,5 @@ os.exit((function(args)
 	local a = 10
 	local b = 20
 	local r = (sum(a, b) + add(a, b))
-	return 0
+	return r
 end)(arg))