Used string with biased hash for double deduplication

Rather than using a separate hash table for doubles, use the same
biases hash approach we use for everything else. Either way works
fine, but there doesn't seem to be any strong reason to use a
different approach for doubles than we use for other cases.

Author: nikic

Zend/Optimizer/compact_literals.c

@@ -100,6 +100,13 @@ static uint32_t add_static_slot(HashTable     *hash,
 	return ret;
 }
 
+static inline void bias_key(zend_string *key, uint32_t bias)
+{
+	/* Add a bias to the hash so we can distinguish string keys
+	 * that would otherwise be the same. */
+	ZSTR_H(key) = zend_string_hash_val(key) + bias;
+}
+
 static zend_string *create_str_cache_key(zval *literal, uint8_t num_related)
 {
 	ZEND_ASSERT(Z_TYPE_P(literal) == IS_STRING);
@@ -124,9 +131,7 @@ static zend_string *create_str_cache_key(zval *literal, uint8_t num_related)
 		ZEND_ASSERT(0 && "Currently not needed");
 	}
 
-	/* Add a bias to the hash so we can distinguish keys
-	 * that would otherwise be the same after concatenation. */
-	ZSTR_H(key) = zend_string_hash_val(key) + num_related - 1;
+	bias_key(key, num_related - 1);
 	return key;
 }
 
@@ -141,7 +146,7 @@ void zend_optimizer_compact_literals(zend_op_array *op_array, zend_optimizer_ctx
 	int l_false = -1;
 	int l_true = -1;
 	int l_empty_arr = -1;
-	HashTable hash, double_hash;
+	HashTable hash;
 	zend_string *key = NULL;
 	void *checkpoint = zend_arena_checkpoint(ctx->arena);
 	int *const_slot, *class_slot, *func_slot, *bind_var_slot, *property_slot, *method_slot;
@@ -285,8 +290,6 @@ void zend_optimizer_compact_literals(zend_op_array *op_array, zend_optimizer_ctx
 		/* Merge equal constants */
 		j = 0;
 		zend_hash_init(&hash, op_array->last_literal, NULL, NULL, 0);
-		/* Use separate hashtable for doubles stored as string keys, to avoid collisions. */
-		zend_hash_init(&double_hash, 0, NULL, NULL, 0);
 		map = (int*)zend_arena_alloc(&ctx->arena, op_array->last_literal * sizeof(int));
 		memset(map, 0, op_array->last_literal * sizeof(int));
 		for (i = 0; i < op_array->last_literal; i++) {
@@ -349,10 +352,9 @@ void zend_optimizer_compact_literals(zend_op_array *op_array, zend_optimizer_ctx
 					} else {
 						ZEND_ASSERT(info[i].num_related == 2);
 						key = zend_string_init(Z_STRVAL(op_array->literals[i+1]), Z_STRLEN(op_array->literals[i+1]), 0);
-						ZSTR_H(key) = ZSTR_HASH(Z_STR(op_array->literals[i+1])) + 100 +
-							info[i].num_related - 1;
-						if ((pos = zend_hash_find(&hash, key)) != NULL
-						 && info[Z_LVAL_P(pos)].num_related == 2) {
+						bias_key(key, 100 + info[i].num_related - 1);
+						if ((pos = zend_hash_find(&hash, key)) != NULL) {
+							ZEND_ASSERT(info[Z_LVAL_P(pos)].num_related == 2);
 							map[i] = Z_LVAL_P(pos);
 							zval_ptr_dtor_nogc(&op_array->literals[i+1]);
 						} else {
@@ -373,18 +375,21 @@ void zend_optimizer_compact_literals(zend_op_array *op_array, zend_optimizer_ctx
 					break;
 				case IS_DOUBLE:
 					ZEND_ASSERT(info[i].num_related == 1);
-					if ((pos = zend_hash_str_find(&double_hash, (char*)&Z_DVAL(op_array->literals[i]), sizeof(double))) != NULL) {
+					key = zend_string_init((char*)&Z_DVAL(op_array->literals[i]), sizeof(double), 0);
+					bias_key(key, 200);
+					if ((pos = zend_hash_find(&hash, key))) {
 						map[i] = Z_LVAL_P(pos);
 					} else {
 						map[i] = j;
 						ZVAL_LONG(&zv, j);
-						zend_hash_str_add_new(&double_hash, (char*)&Z_DVAL(op_array->literals[i]), sizeof(double), &zv);
+						zend_hash_add_new(&hash, key, &zv);
 						if (i != j) {
 							op_array->literals[j] = op_array->literals[i];
 							info[j] = info[i];
 						}
 						j++;
 					}
+					zend_string_release_ex(key, 0);
 					break;
 				case IS_STRING: {
 					key = create_str_cache_key(&op_array->literals[i], info[i].num_related);
@@ -452,7 +457,6 @@ void zend_optimizer_compact_literals(zend_op_array *op_array, zend_optimizer_ctx
 
 		/* Only clean "hash", as it will be reused in the loop below. */
 		zend_hash_clean(&hash);
-		zend_hash_destroy(&double_hash);
 		op_array->last_literal = j;
 
 		const_slot = zend_arena_alloc(&ctx->arena, j * 6 * sizeof(int));