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version 1.1.1.2, 2012/02/21 23:50:25
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version 1.1.1.3, 2012/10/09 09:19:18
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Line 62 JIT. The support is limited to the following hardware
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Line 62 JIT. The support is limited to the following hardware
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| MIPS 32-bit |
MIPS 32-bit |
| Power PC 32-bit and 64-bit |
Power PC 32-bit and 64-bit |
| </pre> |
</pre> |
| The Power PC support is designated as experimental because it has not been | If --enable-jit is set on an unsupported platform, compilation fails. |
| fully tested. If --enable-jit is set on an unsupported platform, compilation | |
| fails. | |
| </P> |
</P> |
| <P> |
<P> |
| A program that is linked with PCRE 8.20 or later can tell if JIT support is |
A program that is linked with PCRE 8.20 or later can tell if JIT support is |
| available by calling <b>pcre_config()</b> with the PCRE_CONFIG_JIT option. The |
available by calling <b>pcre_config()</b> with the PCRE_CONFIG_JIT option. The |
| result is 1 when JIT is available, and 0 otherwise. However, a simple program |
result is 1 when JIT is available, and 0 otherwise. However, a simple program |
| does not need to check this in order to use JIT. The API is implemented in a |
does not need to check this in order to use JIT. The API is implemented in a |
| way that falls back to the ordinary PCRE code if JIT is not available. | way that falls back to the interpretive code if JIT is not available. |
| </P> |
</P> |
| <P> |
<P> |
| If your program may sometimes be linked with versions of PCRE that are older |
If your program may sometimes be linked with versions of PCRE that are older |
|
Line 88 You have to do two things to make use of the JIT suppo
|
Line 86 You have to do two things to make use of the JIT suppo
|
| <b>pcre_exec()</b>. |
<b>pcre_exec()</b>. |
| |
|
| (2) Use <b>pcre_free_study()</b> to free the <b>pcre_extra</b> block when it is |
(2) Use <b>pcre_free_study()</b> to free the <b>pcre_extra</b> block when it is |
| no longer needed instead of just freeing it yourself. This | no longer needed, instead of just freeing it yourself. This |
| ensures that any JIT data is also freed. |
ensures that any JIT data is also freed. |
| </pre> |
</pre> |
| For a program that may be linked with pre-8.20 versions of PCRE, you can insert |
For a program that may be linked with pre-8.20 versions of PCRE, you can insert |
|
Line 106 this to free the study data:
|
Line 104 this to free the study data:
|
| pcre_free(study_ptr); |
pcre_free(study_ptr); |
| #endif |
#endif |
| </pre> |
</pre> |
| |
PCRE_STUDY_JIT_COMPILE requests the JIT compiler to generate code for complete |
| |
matches. If you want to run partial matches using the PCRE_PARTIAL_HARD or |
| |
PCRE_PARTIAL_SOFT options of <b>pcre_exec()</b>, you should set one or both of |
| |
the following options in addition to, or instead of, PCRE_STUDY_JIT_COMPILE |
| |
when you call <b>pcre_study()</b>: |
| |
<pre> |
| |
PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE |
| |
PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE |
| |
</pre> |
| |
The JIT compiler generates different optimized code for each of the three |
| |
modes (normal, soft partial, hard partial). When <b>pcre_exec()</b> is called, |
| |
the appropriate code is run if it is available. Otherwise, the pattern is |
| |
matched using interpretive code. |
| |
</P> |
| |
<P> |
| In some circumstances you may need to call additional functions. These are |
In some circumstances you may need to call additional functions. These are |
| described in the section entitled |
described in the section entitled |
| <a href="#stackcontrol">"Controlling the JIT stack"</a> |
<a href="#stackcontrol">"Controlling the JIT stack"</a> |
| below. |
below. |
| </P> |
</P> |
| <P> |
<P> |
| If JIT support is not available, PCRE_STUDY_JIT_COMPILE is ignored, and no JIT | If JIT support is not available, PCRE_STUDY_JIT_COMPILE etc. are ignored, and |
| data is set up. Otherwise, the compiled pattern is passed to the JIT compiler, | no JIT data is created. Otherwise, the compiled pattern is passed to the JIT |
| which turns it into machine code that executes much faster than the normal | compiler, which turns it into machine code that executes much faster than the |
| interpretive code. When <b>pcre_exec()</b> is passed a <b>pcre_extra</b> block | normal interpretive code. When <b>pcre_exec()</b> is passed a <b>pcre_extra</b> |
| containing a pointer to JIT code, it obeys that instead of the normal code. The | block containing a pointer to JIT code of the appropriate mode (normal or |
| result is identical, but the code runs much faster. | hard/soft partial), it obeys that code instead of running the interpreter. The |
| | result is identical, but the compiled JIT code runs much faster. |
| </P> |
</P> |
| <P> |
<P> |
| There are some <b>pcre_exec()</b> options that are not supported for JIT |
There are some <b>pcre_exec()</b> options that are not supported for JIT |
| execution. There are also some pattern items that JIT cannot handle. Details |
execution. There are also some pattern items that JIT cannot handle. Details |
| are given below. In both cases, execution automatically falls back to the |
are given below. In both cases, execution automatically falls back to the |
| interpretive code. | interpretive code. If you want to know whether JIT was actually used for a |
| | particular match, you should arrange for a JIT callback function to be set up |
| | as described in the section entitled |
| | <a href="#stackcontrol">"Controlling the JIT stack"</a> |
| | below, even if you do not need to supply a non-default JIT stack. Such a |
| | callback function is called whenever JIT code is about to be obeyed. If the |
| | execution options are not right for JIT execution, the callback function is not |
| | obeyed. |
| </P> |
</P> |
| <P> |
<P> |
| If the JIT compiler finds an unsupported item, no JIT data is generated. You |
If the JIT compiler finds an unsupported item, no JIT data is generated. You |
| can find out if JIT execution is available after studying a pattern by calling |
can find out if JIT execution is available after studying a pattern by calling |
| <b>pcre_fullinfo()</b> with the PCRE_INFO_JIT option. A result of 1 means that |
<b>pcre_fullinfo()</b> with the PCRE_INFO_JIT option. A result of 1 means that |
| JIT compilation was successful. A result of 0 means that JIT support is not |
JIT compilation was successful. A result of 0 means that JIT support is not |
| available, or the pattern was not studied with PCRE_STUDY_JIT_COMPILE, or the | available, or the pattern was not studied with PCRE_STUDY_JIT_COMPILE etc., or |
| JIT compiler was not able to handle the pattern. | the JIT compiler was not able to handle the pattern. |
| </P> |
</P> |
| <P> |
<P> |
| Once a pattern has been studied, with or without JIT, it can be used as many |
Once a pattern has been studied, with or without JIT, it can be used as many |
|
Line 140 times as you like for matching different subject strin
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Line 161 times as you like for matching different subject strin
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| <br><a name="SEC5" href="#TOC1">UNSUPPORTED OPTIONS AND PATTERN ITEMS</a><br> |
<br><a name="SEC5" href="#TOC1">UNSUPPORTED OPTIONS AND PATTERN ITEMS</a><br> |
| <P> |
<P> |
| The only <b>pcre_exec()</b> options that are supported for JIT execution are |
The only <b>pcre_exec()</b> options that are supported for JIT execution are |
| PCRE_NO_UTF8_CHECK, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and | PCRE_NO_UTF8_CHECK, PCRE_NO_UTF16_CHECK, PCRE_NOTBOL, PCRE_NOTEOL, |
| PCRE_NOTEMPTY_ATSTART. Note in particular that partial matching is not | PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, PCRE_PARTIAL_HARD, and PCRE_PARTIAL_SOFT. |
| supported. | |
| </P> |
</P> |
| <P> |
<P> |
| The unsupported pattern items are: |
The unsupported pattern items are: |
| <pre> |
<pre> |
| \C match a single byte; not supported in UTF-8 mode |
\C match a single byte; not supported in UTF-8 mode |
| (?Cn) callouts |
(?Cn) callouts |
| (*COMMIT) ) | (*PRUNE) ) |
| (*MARK) ) | (*SKIP) ) backtracking control verbs |
| (*PRUNE) ) the backtracking control verbs | |
| (*SKIP) ) | |
| (*THEN) ) |
(*THEN) ) |
| </pre> |
</pre> |
| Support for some of these may be added in future. |
Support for some of these may be added in future. |
|
Line 221 should use. Its arguments are as follows:
|
Line 239 should use. Its arguments are as follows:
|
| void *data |
void *data |
| </pre> |
</pre> |
| The <i>extra</i> argument must be the result of studying a pattern with |
The <i>extra</i> argument must be the result of studying a pattern with |
| PCRE_STUDY_JIT_COMPILE. There are three cases for the values of the other two | PCRE_STUDY_JIT_COMPILE etc. There are three cases for the values of the other |
| options: | two options: |
| <pre> |
<pre> |
| (1) If <i>callback</i> is NULL and <i>data</i> is NULL, an internal 32K block |
(1) If <i>callback</i> is NULL and <i>data</i> is NULL, an internal 32K block |
| on the machine stack is used. |
on the machine stack is used. |
|
Line 230 options:
|
Line 248 options:
|
| (2) If <i>callback</i> is NULL and <i>data</i> is not NULL, <i>data</i> must be |
(2) If <i>callback</i> is NULL and <i>data</i> is not NULL, <i>data</i> must be |
| a valid JIT stack, the result of calling <b>pcre_jit_stack_alloc()</b>. |
a valid JIT stack, the result of calling <b>pcre_jit_stack_alloc()</b>. |
| |
|
| (3) If <i>callback</i> not NULL, it must point to a function that is called | (3) If <i>callback</i> is not NULL, it must point to a function that is |
| with <i>data</i> as an argument at the start of matching, in order to | called with <i>data</i> as an argument at the start of matching, in |
| set up a JIT stack. If the result is NULL, the internal 32K stack | order to set up a JIT stack. If the return from the callback |
| is used; otherwise the return value must be a valid JIT stack, | function is NULL, the internal 32K stack is used; otherwise the |
| the result of calling <b>pcre_jit_stack_alloc()</b>. | return value must be a valid JIT stack, the result of calling |
| | <b>pcre_jit_stack_alloc()</b>. |
| </pre> |
</pre> |
| You may safely assign the same JIT stack to more than one pattern, as long as | A callback function is obeyed whenever JIT code is about to be run; it is not |
| they are all matched sequentially in the same thread. In a multithread | obeyed when <b>pcre_exec()</b> is called with options that are incompatible for |
| application, each thread must use its own JIT stack. | JIT execution. A callback function can therefore be used to determine whether a |
| | match operation was executed by JIT or by the interpreter. |
| </P> |
</P> |
| <P> |
<P> |
| Strictly speaking, even more is allowed. You can assign the same stack to any | You may safely use the same JIT stack for more than one pattern (either by |
| number of patterns as long as they are not used for matching by multiple | assigning directly or by callback), as long as the patterns are all matched |
| | sequentially in the same thread. In a multithread application, if you do not |
| | specify a JIT stack, or if you assign or pass back NULL from a callback, that |
| | is thread-safe, because each thread has its own machine stack. However, if you |
| | assign or pass back a non-NULL JIT stack, this must be a different stack for |
| | each thread so that the application is thread-safe. |
| | </P> |
| | <P> |
| | Strictly speaking, even more is allowed. You can assign the same non-NULL stack |
| | to any number of patterns as long as they are not used for matching by multiple |
| threads at the same time. For example, you can assign the same stack to all |
threads at the same time. For example, you can assign the same stack to all |
| compiled patterns, and use a global mutex in the callback to wait until the |
compiled patterns, and use a global mutex in the callback to wait until the |
| stack is available for use. However, this is an inefficient solution, and | stack is available for use. However, this is an inefficient solution, and not |
| not recommended. | recommended. |
| </P> |
</P> |
| <P> |
<P> |
| This is a suggestion for how a typical multithreaded program might operate: | This is a suggestion for how a multithreaded program that needs to set up |
| | non-default JIT stacks might operate: |
| <pre> |
<pre> |
| During thread initalization |
During thread initalization |
| thread_local_var = pcre_jit_stack_alloc(...) |
thread_local_var = pcre_jit_stack_alloc(...) |
|
Line 263 This is a suggestion for how a typical multithreaded p
|
Line 293 This is a suggestion for how a typical multithreaded p
|
| All the functions described in this section do nothing if JIT is not available, |
All the functions described in this section do nothing if JIT is not available, |
| and <b>pcre_assign_jit_stack()</b> does nothing unless the <b>extra</b> argument |
and <b>pcre_assign_jit_stack()</b> does nothing unless the <b>extra</b> argument |
| is non-NULL and points to a <b>pcre_extra</b> block that is the result of a |
is non-NULL and points to a <b>pcre_extra</b> block that is the result of a |
| successful study with PCRE_STUDY_JIT_COMPILE. | successful study with PCRE_STUDY_JIT_COMPILE etc. |
| <a name="stackfaq"></a></P> |
<a name="stackfaq"></a></P> |
| <br><a name="SEC9" href="#TOC1">JIT STACK FAQ</a><br> |
<br><a name="SEC9" href="#TOC1">JIT STACK FAQ</a><br> |
| <P> |
<P> |
|
Line 329 pattern causes stack overflow with a stack of 1M? Is t
|
Line 359 pattern causes stack overflow with a stack of 1M? Is t
|
| stack is freed? |
stack is freed? |
| <br> |
<br> |
| <br> |
<br> |
| Especially on embedded sytems, it might be a good idea to release | Especially on embedded sytems, it might be a good idea to release memory |
| memory sometimes without freeing the stack. There is no API for this at the | sometimes without freeing the stack. There is no API for this at the moment. |
| moment. Probably a function call which returns with the currently allocated | Probably a function call which returns with the currently allocated memory for |
| memory for any stack and another which allows releasing memory (shrinking the | any stack and another which allows releasing memory (shrinking the stack) would |
| stack) would be a good idea if someone needs this. | be a good idea if someone needs this. |
| </P> |
</P> |
| <P> |
<P> |
| (7) This is too much of a headache. Isn't there any better solution for JIT |
(7) This is too much of a headache. Isn't there any better solution for JIT |
|
Line 383 Cambridge CB2 3QH, England.
|
Line 413 Cambridge CB2 3QH, England.
|
| </P> |
</P> |
| <br><a name="SEC13" href="#TOC1">REVISION</a><br> |
<br><a name="SEC13" href="#TOC1">REVISION</a><br> |
| <P> |
<P> |
| Last updated: 08 January 2012 | Last updated: 04 May 2012 |
| <br> |
<br> |
| Copyright © 1997-2012 University of Cambridge. |
Copyright © 1997-2012 University of Cambridge. |
| <br> |
<br> |
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