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

According to constants patch, it definitely will break PHP encoders and may be opcode caches, but as you mentioned the compiler_option will solve the issue. In this case we probable may substitute any constants (not only persistent). Anyway I don't see a big reason for special handling of TRUE/FALSE/NULL in scanner. Also it'll break "function true(){}" and may be something else (I'm not sure if it's good or bad :). Multiple long looks fine, but on which systems did you test it? I'll try to take a deeper look into string optimization patch today or tomorrow. 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