Add specialized handler for checking if identical to string

This has a large performance benefit for the below snippet (0.64s vs 0.94s),
and a small benefit for `$alwaysStr == 'notnumeric'`/`$s = 'other'`
(for 1000 runs of test('test'))

- If the literal is non-numeric and the variable is a string,
  `==` behaves identically to `===`, so reuse the opcode.

This is similar to what was suggested in php#4900

- Avoiding types with __destruct or notices simplifies the specialized
  implementation and avoids expensive exception handling.
- TMPVARCV doesn't support FREE_OP1() - use TMPVAR|CV instead.

```
function test(string $s) : int {
    $total = 0;
    for ($i = 0; $i < 100000; $i++) {
        if ($s === "first") {
            $total++;
            $s = null;
        }
    }
    return $total;
}
```

Zend/zend_hash.h

@@ -371,6 +371,16 @@ static zend_always_inline int _zend_handle_numeric_str(const char *key, size_t l
 	return _zend_handle_numeric_str_ex(key, length, idx);
 }
 
+static zend_always_inline int zend_is_numeric_string_literal(const char *key, size_t length)
+{
+	zend_ulong idx;
+	return _zend_handle_numeric_str_ex(key, length, &idx);
+}
+
+static zend_always_inline int zend_is_numeric_string(const zend_string *str) {
+	return zend_is_numeric_string_literal(ZSTR_VAL(str), ZSTR_LEN(str));
+}
+
 #define ZEND_HANDLE_NUMERIC_STR(key, length, idx) \
 	_zend_handle_numeric_str(key, length, &idx)
 

Zend/zend_vm_def.h

@@ -9190,6 +9190,25 @@ ZEND_VM_HOT_TYPE_SPEC_HANDLER(ZEND_IS_EQUAL|ZEND_IS_IDENTICAL, (op1_info == MAY_
 	ZEND_VM_SMART_BRANCH(result, 0);
 }
 
+ZEND_VM_HOT_TYPE_SPEC_HANDLER(ZEND_IS_IDENTICAL|ZEND_IS_EQUAL, op->op1_type != IS_CONST && op->op2_type == IS_CONST && (op2_info == MAY_BE_STRING && (opcode == ZEND_IS_IDENTICAL ? !(op1_info & ~(MAY_BE_NULL|MAY_BE_FALSE|MAY_BE_TRUE|MAY_BE_LONG|MAY_BE_STRING)) : (op1_info == MAY_BE_STRING && !zend_is_numeric_string(Z_STR_P(RT_CONSTANT(op, op->op2)))))), ZEND_IS_IDENTICAL_STRING, TMPVAR|CV, CONST, SPEC(COMMUTATIVE))
+{
+	USE_OPLINE
+	zval *op1, *op2;
+	int result;
+
+	op1 = GET_OP1_ZVAL_PTR_UNDEF(BP_VAR_R);
+	op2 = RT_CONSTANT(opline, opline->op2);
+	if (Z_TYPE_P(op1) == IS_STRING) {
+		result = zend_string_equals(Z_STR_P(op1), Z_STR_P(op2));
+		if (OP1_TYPE & (IS_TMP_VAR|IS_VAR)) {
+			zval_ptr_dtor_str(op1);
+		}
+	} else {
+		result = 0;
+	}
+	ZEND_VM_SMART_BRANCH(result, 0);
+}
+
 ZEND_VM_HOT_TYPE_SPEC_HANDLER(ZEND_IS_NOT_EQUAL|ZEND_IS_NOT_IDENTICAL, (op1_info == MAY_BE_LONG && op2_info == MAY_BE_LONG), ZEND_IS_NOT_EQUAL_LONG, CONST|TMPVARCV, CONST|TMPVARCV, SPEC(SMART_BRANCH,NO_CONST_CONST,COMMUTATIVE))
 {
 	USE_OPLINE
@@ -9214,6 +9233,26 @@ ZEND_VM_HOT_TYPE_SPEC_HANDLER(ZEND_IS_NOT_EQUAL|ZEND_IS_NOT_IDENTICAL, (op1_info
 	ZEND_VM_SMART_BRANCH(result, 0);
 }
 
+ZEND_VM_HOT_TYPE_SPEC_HANDLER(ZEND_IS_NOT_IDENTICAL|ZEND_IS_NOT_EQUAL, op->op1_type != IS_CONST && op->op2_type == IS_CONST && (op2_info == MAY_BE_STRING && (opcode == ZEND_IS_NOT_IDENTICAL ? !(op1_info & ~(MAY_BE_NULL|MAY_BE_FALSE|MAY_BE_TRUE|MAY_BE_LONG|MAY_BE_STRING)) : (op1_info == MAY_BE_STRING && !zend_is_numeric_string(Z_STR_P(RT_CONSTANT(op, op->op2)))))), ZEND_IS_NOT_IDENTICAL_STRING, TMPVAR|CV, CONST, SPEC(COMMUTATIVE))
+{
+	USE_OPLINE
+	zval *op1, *op2;
+	int result;
+
+	op1 = GET_OP1_ZVAL_PTR_UNDEF(BP_VAR_R);
+	if (Z_TYPE_P(op1) == IS_STRING) {
+		op2 = RT_CONSTANT(opline, opline->op2);
+		result = !zend_string_equals(Z_STR_P(op1), Z_STR_P(op2));
+		if (OP1_TYPE & (IS_TMP_VAR|IS_VAR)) {
+			zval_ptr_dtor_str(op1);
+		}
+	} else {
+		result = 1;
+	}
+
+	ZEND_VM_SMART_BRANCH(result, 0);
+}
+
 ZEND_VM_TYPE_SPEC_HANDLER(ZEND_IS_IDENTICAL, op->op1_type == IS_CV && (op->op2_type & (IS_CONST|IS_CV)) && !(op1_info & (MAY_BE_UNDEF|MAY_BE_REF)) && !(op2_info & (MAY_BE_UNDEF|MAY_BE_REF)), ZEND_IS_IDENTICAL_NOTHROW, CV, CONST|CV, SPEC(COMMUTATIVE))
 {
 	/* This is declared below the specializations for MAY_BE_LONG/MAY_BE_DOUBLE so those will be used instead if possible. */