fix a bug in selecting loop control variables.

No union integer fields should be selected as loop control variable if another field is pointer because stepping could potentially invalidate the pointer analysis

src/StatementFor.cpp

@@ -147,10 +147,6 @@ StatementFor::make_iteration(CGContext& cg_context, StatementAssign*& init, Expr
 		var = VariableSelector::SelectLoopCtrlVar(cg_context, invalid_vars); 
 		ERROR_GUARD(NULL);
 		if (var->is_volatile() || 
-			// disallow an integer field of an union, which also has a pointer field, to be IV because
-			// increment IV would cause the pointer to be invalid, and the current points-to analysis
-			// simply assumes loop stepping has no pointer effect
-			(var->is_inside_union_field() && var->get_top_container()->type->contain_pointer_field()) ) {
 			invalid_vars.push_back(var);
 		} else {
 			break;

src/Type.cpp

@@ -439,10 +439,9 @@ Type::is_volatile_struct_union() const
 bool
 Type::has_int_field() const
 {
-	if (!is_aggregate()) return false; 
+	if (is_int()) return true; 
 	for (size_t i=0; i<fields.size(); ++i) {
 		const Type* t = fields[i];
-		if (t->is_int()) return true;
 		if (t->has_int_field()) return true;
 	}
 	return false;

src/VariableSelector.cpp

@@ -1097,18 +1097,29 @@ Variable *
 VariableSelector::SelectLoopCtrlVar(const CGContext &cg_context, const vector<const Variable*>& invalid_vars)
 {
 	// Note that many of the functions that select `var' can return null, if
-	const Type* type = get_int_type();  
-	//eVariableScope scope = VariableSelectionProbability(eNewValue);
-	//ERROR_GUARD(NULL);
+	const Type* type = get_int_type();   
 	vector<Variable*> vars;
-	find_all_non_array_visible_vars(cg_context.get_current_block(), vars); 
+	find_all_non_array_visible_vars(cg_context.get_current_block(), vars);
+	// remove union variables that have both integer field(s) and pointer field(s)  
+	// because incrementing the integer field causes the pointer to be invalid, and the current 
+	// points-to analysis simply assumes loop stepping has no pointer effect
+	size_t len = vars.size();
+	for (size_t i=0; i<len; i++) { 
+		if (vars[i]->type && 
+			(!vars[i]->type->has_int_field() ||		// remove variables isn't (or doesn't contain) integers 
+			(vars[i]->type->eType == eUnion && 
+			vars[i]->type->contain_pointer_field()))) {
+			vars.erase(vars.begin() + i);
+			i--;
+			len--;
+		}
+	}
 	Variable* var = choose_var(vars, Effect::WRITE, cg_context, type, 0, eConvert, invalid_vars, true);
 	ERROR_GUARD(NULL);
 	if (var == NULL) {
 		var = GenerateNewGlobal(Effect::WRITE, cg_context, type, 0);
 	}
 	return var;
-	//return select(Effect::WRITE, cg_context, type, 0, invalid_vars, eConvert, scope);
 }
 
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