Add assertion in liveliness computation

nikic · nikic · commit ed14019e8c0c · 2015-07-08T12:00:39.000+02:00
Assert that a live-range does not start, while one for the same
variable is already active.

To satisfy this constraint, explicitly exclude writes from JMP_SET
and COALESCE. They were previously also handled correctly, because
their result variable was only killed after the second write to it
after the false branch. This just makes it more explicit.
diff --git a/Zend/zend_opcode.c b/Zend/zend_opcode.c
@@ -941,9 +941,12 @@ static zend_always_inline uint32_t *generate_var_liveliness_info_ex(zend_op_arra
 			&& opline->opcode != ZEND_BOOL
 			&& opline->opcode != ZEND_JMPZ_EX
 			&& opline->opcode != ZEND_JMPNZ_EX
-			/* these two consecutive ops appear on ternary,
-			 * the result of true branch is undefined for false branch */
+			/* These opcodes write the result of the true branch of a ternary, short
+			 * ternary or coalesce and are immediately followed by the instructions
+			 * for the false branch (where this result is not live) */
 			&& (opline->opcode != ZEND_QM_ASSIGN || (opline + 1)->opcode != ZEND_JMP)
+			&& opline->opcode != ZEND_JMP_SET
+			&& opline->opcode != ZEND_COALESCE
 			/* exception for opcache, it might nowhere use the temporary
 			 * (anyway bool, so no need to free) */
 			&& opline->opcode != ZEND_CASE
@@ -959,14 +962,17 @@ static zend_always_inline uint32_t *generate_var_liveliness_info_ex(zend_op_arra
 			&& opline->opcode != ZEND_DECLARE_INHERITED_CLASS
 			&& opline->opcode != ZEND_DECLARE_INHERITED_CLASS_DELAYED
 			&& opline->opcode != ZEND_DECLARE_ANON_CLASS
-			&& opline->opcode != ZEND_DECLARE_ANON_INHERITED_CLASS) {
+			&& opline->opcode != ZEND_DECLARE_ANON_INHERITED_CLASS
+		) {
 			if (done_pass_two) {
 				var = EX_VAR_TO_NUM(opline->result.var) - op_array->last_var;
 			} else {
 				var = opline->result.var;
 			}
-			/* Objects created via ZEND_NEW are only fully initialized after the DO_FCALL (constructor call) */
+			ZEND_ASSERT(Tstart[var] == (unsigned) -1);
 			if (opline->opcode == ZEND_NEW) {
+				/* Objects created via ZEND_NEW are only fully initialized
+				 * after the DO_FCALL (constructor call) */
 				Tstart[var] = opline->op2.opline_num - 1;
 			} else {
 				Tstart[var] = opline - op_array->opcodes;
