New optimization idea; was: No runtime fetching of built-in global constants

Hi Matt, At first as you are a scanner expert, I would like you to look into another optimization idea. Probably for historical reason PHP supports shebang lines (#! /usr/bin/php) on top of php files. Especially to handle them PHP (CGI/FastCGI/CLI) opens file and check for it. So even with opcode caches FastCGI PHP does open syscall for the requested script, however with opcode caches it's absolutely useless. In case PHP scanner will handle shebang lines itself, we will able to save this syscall. I never had time and enough flex/re2c knowledge to implement this idea myself. May be you'll able to look into the problem. In case you find a simple solution we will able to do it in php-5.3. Most PHP hosters and large sites use FastCGI with opcode caches (it is also the primary way for MS Windows users), so this optimization is really important. [see below] Matt Wilmas wrote:

Hi Dmitry, I saw that you commited this patch, with the addition of only replacing persistent constants (just mentioning for others on the list). The attached patches have a few tweaks: The main thing I noticed is that if "something" creates a persistent, case-INsensitive constant (any of those in "standard" PHP, besides TRUE/FALSE/NULL?), it could still wrongly be substituted. My change eliminates that possibility.

After yesterday's subbotnik I'm so stupid so cannot understand simple tings. :) Could you point me into the exact part of the patch.

Checking Z_TYPE(c->value) != IS_CONSTANT[_ARRAY] isn't needed with the persistent check now, is it?

I think you are right, but it's better to have this checks, because nobody prohibit to create array constants in extensions.

From orginal patch (zend_constants.c part), the memcmp(...) != 0 isn't needed as it will always be true. If it wasn't, the *first* hash lookup wouldn't have failed. :-) Like I said in the original message, it's old code from a long time ago, but was never removed...

I'll check it with more clear head. Thanks. Dmitry.

- Matt ----- Original Message ----- From: "Dmitry Stogov" Sent: Thursday, July 24, 2008

I would propose the attached patch for this optimization. Opcode caches and encoders will have to disable this optimization with ZEND_COMPILE_NO_CONSTANT_SUBSTITUTION Any objections? Thanks. Dmitry.

---------------------------------------------------------------------------- ----

Index: Zend/zend_compile.c =================================================================== RCS file: /repository/ZendEngine2/zend_compile.c,v retrieving revision 1.647.2.27.2.41.2.74 diff -u -p -d -r1.647.2.27.2.41.2.74 zend_compile.c --- Zend/zend_compile.c 24 Jul 2008 11:47:49 -0000 1.647.2.27.2.41.2.74 +++ Zend/zend_compile.c 24 Jul 2008 14:40:12 -0000 @@ -3804,6 +3804,12 @@ static zend_constant* zend_get_ct_const( if (c->flags & CONST_CT_SUBST) { return c; } + if (!CG(current_namespace) &&

+     !(CG(compiler_options) & ZEND_COMPILE_NO_CONSTANT_SUBSTITUTION) &&
+     Z_TYPE(c->value) != IS_CONSTANT &&
+     Z_TYPE(c->value) != IS_CONSTANT_ARRAY) {

+ return c; + } return NULL; } /* }}} */ @@ -5169,12 +5175,14 @@ void zend_do_use(znode *ns_name, znode * void zend_do_declare_constant(znode *name, znode *value TSRMLS_DC) /*

{{{ */

{ zend_op *opline; + zend_constant *c; if(Z_TYPE(value->u.constant) == IS_CONSTANT_ARRAY) { zend_error(E_COMPILE_ERROR, "Arrays are not allowed as constants"); } - if (zend_get_ct_const(&name->u.constant TSRMLS_CC)) { + c = zend_get_ct_const(&name->u.constant TSRMLS_CC); + if (c && (c->flags & CONST_CT_SUBST)) { zend_error(E_COMPILE_ERROR, "Cannot redeclare constant '%s'",

Z_STRVAL(name->u.constant));

} Index: Zend/zend_compile.h =================================================================== RCS file: /repository/ZendEngine2/zend_compile.h,v retrieving revision 1.316.2.8.2.12.2.27 diff -u -p -d -r1.316.2.8.2.12.2.27 zend_compile.h --- Zend/zend_compile.h 24 Jul 2008 11:47:49 -0000 1.316.2.8.2.12.2.27 +++ Zend/zend_compile.h 24 Jul 2008 14:40:13 -0000 @@ -762,6 +762,9 @@ END_EXTERN_C() /* generate ZEND_DECLARE_INHERITED_CLASS_DELAYED opcode to delay early

binding */

#define ZEND_COMPILE_DELAYED_BINDING (1<<4) +/* disable constant substitution at compile-time */ +#define ZEND_COMPILE_NO_CONSTANT_SUBSTITUTION (1<<5) + /* The default value for CG(compiler_options) */ #define ZEND_COMPILE_DEFAULT ZEND_COMPILE_HANDLE_OP_ARRAY