Re: [PATCH] No runtime fetching of built-in global constants

Thank you for noticing SID issue. So it seems like we able to substitute only persistent constants. Thanks. Dmitry. Matt Wilmas wrote:

Hi again Dmitry, Well, that should get the main runtime optimization job done just as well. :-) I was just trying for more compile-time improvement also (it was definitely measurable with fake tests), especially for those not using an opcode cache, with no lookup needed for the 3 basic constants, and only one without lowercasing for others. One other thing it looks like with your patch, to be careful of, is wrongly substituting SID (session id) like I mentioned in the previous message, or other case-insensitive constants that could match at compile time, to later be defined as case sensitive, which should have priority. Know what I mean? Thanks, 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. Matt Wilmas wrote:

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

Hi Matt, Sorry if I missed it.

No problem. :-)

Does this patch make any performance difference? I assume it saves on hash lookup during compilation and its really insignificant time. However it add new scanner rules which may slowdown the whole scanner. For now I don't see a big reason, but may be I didn't see something.

Yes, I tried to explain the differences in the original message (below).

In

runtime, FETCH_CONSTANT is saved for the "built-in, global constants" (CONST_PERSISTENT). During compilation, no hash lookup is needed for TRUE/FALSE/NULL since they are caught by the scanner, as you saw. The compile-time hash lookups were added when you eliminated runtime

fetching

for TRUE/FALSE/NULL a couple years ago, which has since been looking up

the

other built-in constants too and discarding them, so I just use them.

:-)

Also, right now if the constant isn't found (zend_get_ct_const()),

there's

lowercasing and a second lookup -- only for catching case-insensitive TRUE/FALSE/NULL! One thing I was wondering about is if this would cause a problem for

opcode

caches if they need to know it's really a "constant constant" and not a "literal constant." If so, can probably have a compiler_options flag to disable my compile-time substitution, and the opcode cache can do what

it

wants (substitution with own optimizer, etc.).

Do you have any other "postponed" patches? I remember something about string optimizations and long multiply.

Yeah. :-) The multiply long one [1] is a pretty small thing that

probably

should be reviewed for a decision (MM's safe_address() function

especially),

though it does speed up mul_function() (* operator) on more platforms. The "string changes/optimizations" patch [2] is mostly fine, I think.

Just

wondering if it's OK to remove the INIT_STRING opcode. BTW, it has

changes

that make the scanner simpler/smaller if you're concerned about the constants patch adding a few rules. ;-D [1] http://marc.info/?l=php-internals&m=121630449331340&w=2 [2] http://marc.info/?l=php-internals&m=121569400218314&w=2

Thanks. Dmitry.

Thanks, Matt

Matt Wilmas wrote:

Hi all, Never heard anything about this optimization after sending it 3 months

ago

(should've sent a follow-up sooner)... Is this something that can be done? Dmitry? Details in original

message.

Patch is unchanged, I just updated them for the current file versions. http://realplain.com/php/const_ct_optimization.diff http://realplain.com/php/const_ct_optimization_5_3.diff Thanks, Matt ----- Original Message ----- From: "Matt Wilmas" Sent: Friday, April 18, 2008

Hi all, I changed things so that the many "built-in" constants

(CONST_PERSISTENT

ones) will be replaced at compile-time, saving the FETCH_CONSTANT

opcode,

if

these changes are usable. This was added for TRUE/FALSE/NULL 2 years

ago,

but seems like it can be done for "lots" of others too. Since the change 2 years ago, other constants have been getting

looked

up

also, but just discarded. And if a constant wasn't found, its name

was

lowercased and looked up again (for case-insensitive

TRUE/FALSE/NULL).

Lowercasing has been removed, since case-insensitive constants can't

be

done

(guess an exception was made for TRUE/FALSE/NULL :-)), and

TRUE/FALSE/NULL

get flagged in the scanner (not reserved words, which Marcus did

briefly a

few years ago), skipping a hash lookup. BTW, to get this

compile-time

optimization in a namespace, it needs to be prefixed (::CONSTANT). I also removed an unnecessary memcmp() in zend_get_constant() -- old

code

that was needed a long time ago, it appears. http://realplain.com/php/const_ct_optimization.diff http://realplain.com/php/const_ct_optimization_5_3.diff Thoughts? Thanks, Matt

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

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