Fix compile-time optimization of NAN comparisons

Zend/zend_operators.c

@@ -2151,6 +2151,16 @@ ZEND_API int ZEND_FASTCALL is_not_equal_function(zval *result, zval *op1, zval *
 
 ZEND_API int ZEND_FASTCALL is_smaller_function(zval *result, zval *op1, zval *op2) /* {{{ */
 {
+	if (UNEXPECTED((Z_TYPE_P(op1) == IS_DOUBLE) && isnan(Z_DVAL_P(op1)))) {
+		ZVAL_FALSE(result);
+		return SUCCESS;
+	}
+
+	if (UNEXPECTED((Z_TYPE_P(op2) == IS_DOUBLE) && isnan(Z_DVAL_P(op2)))) {
+		ZVAL_FALSE(result);
+		return SUCCESS;
+	}
+
 	if (compare_function(result, op1, op2) == FAILURE) {
 		return FAILURE;
 	}
@@ -2161,6 +2171,16 @@ ZEND_API int ZEND_FASTCALL is_smaller_function(zval *result, zval *op1, zval *op
 
 ZEND_API int ZEND_FASTCALL is_smaller_or_equal_function(zval *result, zval *op1, zval *op2) /* {{{ */
 {
+	if (UNEXPECTED((Z_TYPE_P(op1) == IS_DOUBLE) && isnan(Z_DVAL_P(op1)))) {
+		ZVAL_FALSE(result);
+		return SUCCESS;
+	}
+
+	if (UNEXPECTED((Z_TYPE_P(op2) == IS_DOUBLE) && isnan(Z_DVAL_P(op2)))) {
+		ZVAL_FALSE(result);
+		return SUCCESS;
+	}
+
 	if (compare_function(result, op1, op2) == FAILURE) {
 		return FAILURE;
 	}

tests/lang/operators/nan-comparison-false.phpt

@@ -0,0 +1,29 @@
+--TEST--
+Comparisons with NAN should yield false, even at compile-time
+--FILE--
+<?php
+
+echo "** CONST\n";
+var_dump(0 < NAN);
+var_dump(0 <= NAN);
+var_dump(0 > NAN);
+var_dump(0 >= NAN);
+
+echo "** VAR\n";
+$nan = NAN;
+var_dump(0 < $nan);
+var_dump(0 <= $nan);
+var_dump(0 > $nan);
+var_dump(0 >= $nan);
+
+--EXPECT--
+** CONST
+bool(false)
+bool(false)
+bool(false)
+bool(false)
+** VAR
+bool(false)
+bool(false)
+bool(false)
+bool(false)