String rc1 opts #12
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String rc1 opts #12
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## Introduction This implements a more generic version of the in-place modification I first tried in phpGH-11060. We decided to limit that PR to RC1 optimisations of some array functions only, and not do the in-place $variable optimisation in that way because of issues. This patch overcomes those issues and builds on the previous one. With this patch, any internal function that supports RC1 optimisations automatically gets the optimisation for in-place variable modifications. Contrary to the previous approach, this is compatible with exceptions. Furthermore, this approach also allows userland functions to benefit from this optimisation. e.g. the following code will not take a copy of the array with this patch: ``` function foo($array) { $array[1] = 1; } function bar() { $array = ...; $array = foo($array); } ``` Right now the impact on the benchmark suite isn't that high. The reason is that only a handful of functions within PHP optimise for RC1 cases, and the array sizes for those cases are fairly small. When more support for these cases are added, the benefit from this patch will increase. I've added a micro benchmark for array operations that shows the effect of this optimisation. ## Implementation The optimiser already tracks which SSA variables have a value that doesn't matter with the no_val field. By changing ZEND_SEND_VAR to redefine op1, we automatically know if the variable will ever be used again without being overwritten by looking at the no_val field. If the no_val field is set, the variable may hold a string/array and the refcount may be 1, we set a flag on the ZEND_SEND_VAR(_EX) opline to indicate that it may avoid a copy. The flag is stored in extended_value. There are two new VM type spec handlers for this that check for the flag: one for ZEND_SEND_VAR and one for ZEND_SEND_VAR_EX. ## Limitations * The optimisation isn't performed on arguments. This is because the optimisation would be externally visible, which is undesirable. Unfortunately, this is also the case where a lot of optimisation opportunity lies. Nonetheless, even with this limitation it seems like it can help a lot. * The optimisation does not apply to functions using indirect variable access (e.g. variable-variables, compact()) and vararg functions.
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We can't unconditionally allow inplace modification in zend_string_toupper_ex and zend_string_tolower_ex because their API contract expects a copy.
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nielsdos
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Oct 13, 2024
even without sanitizers, it is reproducible but with the following
```
<?php
$g = gmp_init(256);
var_dump(gmp_pow($g, PHP_INT_MAX));
```
we get this
```
AddressSanitizer:DEADLYSIGNAL
=================================================================
==286922==ERROR: AddressSanitizer: FPE on unknown address 0x03e8000460ca (pc 0x7faf6c69de5c bp 0x400000000000004 sp 0x7ffe9843c740 T0)
#0 0x7faf6c69de5c in __pthread_kill_implementation nptl/pthread_kill.c:44
#1 0x7faf6c649c81 in __GI_raise ../sysdeps/posix/raise.c:26
#2 0x7faf6db9386c in __gmp_exception (/lib/x86_64-linux-gnu/libgmp.so.10+0xd86c) (BuildId: 1af68a49fe041a5bb48a2915c3d47541f713bb38)
#3 0x7faf6db938d3 in __gmp_overflow_in_mpz (/lib/x86_64-linux-gnu/libgmp.so.10+0xd8d3) (BuildId: 1af68a49fe041a5bb48a2915c3d47541f713bb38)
#4 0x7faf6dbac95c in __gmpz_realloc (/lib/x86_64-linux-gnu/libgmp.so.10+0x2695c) (BuildId: 1af68a49fe041a5bb48a2915c3d47541f713bb38)
#5 0x7faf6dba9038 in __gmpz_n_pow_ui (/lib/x86_64-linux-gnu/libgmp.so.10+0x23038) (BuildId: 1af68a49fe041a5bb48a2915c3d47541f713bb38)
#6 0x5565ae1ccd9f in zif_gmp_pow /home/dcarlier/Contribs/php-src/ext/gmp/gmp.c:1286
#7 0x5565aee96ea9 in ZEND_DO_ICALL_SPEC_RETVAL_USED_HANDLER /home/dcarlier/Contribs/php-src/Zend/zend_vm_execute.h:1312
#8 0x5565af144320 in execute_ex /home/dcarlier/Contribs/php-src/Zend/zend_vm_execute.h:56075
#9 0x5565af160f07 in zend_execute /home/dcarlier/Contribs/php-src/Zend/zend_vm_execute.h:60439
#10 0x5565aed6fafe in zend_execute_scripts /home/dcarlier/Contribs/php-src/Zend/zend.c:1842
#11 0x5565aeae70a8 in php_execute_script /home/dcarlier/Contribs/php-src/main/main.c:2578
#12 0x5565af532f4e in do_cli /home/dcarlier/Contribs/php-src/sapi/cli/php_cli.c:964
#13 0x5565af535877 in main /home/dcarlier/Contribs/php-src/sapi/cli/php_cli.c:1334
#14 0x7faf6c633d67 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
#15 0x7faf6c633e24 in __libc_start_main_impl ../csu/libc-start.c:360
#16 0x5565adc04040 in _start (/home/dcarlier/Contribs/php-src/sapi/cli/php+0x2604040) (BuildId: 949049955bdf8b7197390b1978a1dfc3ef6fdf38)
AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: FPE nptl/pthread_kill.c:44 in __pthread_kill_implementation
==286922==ABORTING
```
nielsdos
pushed a commit
that referenced
this pull request
Oct 26, 2024
even without sanitizers, it is reproducible but with the following
```
<?php
$g = gmp_init(256);
var_dump(gmp_pow($g, PHP_INT_MAX));
```
we get this
```
AddressSanitizer:DEADLYSIGNAL
=================================================================
==286922==ERROR: AddressSanitizer: FPE on unknown address 0x03e8000460ca (pc 0x7faf6c69de5c bp 0x400000000000004 sp 0x7ffe9843c740 T0)
#0 0x7faf6c69de5c in __pthread_kill_implementation nptl/pthread_kill.c:44
#1 0x7faf6c649c81 in __GI_raise ../sysdeps/posix/raise.c:26
#2 0x7faf6db9386c in __gmp_exception (/lib/x86_64-linux-gnu/libgmp.so.10+0xd86c) (BuildId: 1af68a49fe041a5bb48a2915c3d47541f713bb38)
#3 0x7faf6db938d3 in __gmp_overflow_in_mpz (/lib/x86_64-linux-gnu/libgmp.so.10+0xd8d3) (BuildId: 1af68a49fe041a5bb48a2915c3d47541f713bb38)
#4 0x7faf6dbac95c in __gmpz_realloc (/lib/x86_64-linux-gnu/libgmp.so.10+0x2695c) (BuildId: 1af68a49fe041a5bb48a2915c3d47541f713bb38)
#5 0x7faf6dba9038 in __gmpz_n_pow_ui (/lib/x86_64-linux-gnu/libgmp.so.10+0x23038) (BuildId: 1af68a49fe041a5bb48a2915c3d47541f713bb38)
#6 0x5565ae1ccd9f in zif_gmp_pow /home/dcarlier/Contribs/php-src/ext/gmp/gmp.c:1286
#7 0x5565aee96ea9 in ZEND_DO_ICALL_SPEC_RETVAL_USED_HANDLER /home/dcarlier/Contribs/php-src/Zend/zend_vm_execute.h:1312
#8 0x5565af144320 in execute_ex /home/dcarlier/Contribs/php-src/Zend/zend_vm_execute.h:56075
#9 0x5565af160f07 in zend_execute /home/dcarlier/Contribs/php-src/Zend/zend_vm_execute.h:60439
#10 0x5565aed6fafe in zend_execute_scripts /home/dcarlier/Contribs/php-src/Zend/zend.c:1842
#11 0x5565aeae70a8 in php_execute_script /home/dcarlier/Contribs/php-src/main/main.c:2578
#12 0x5565af532f4e in do_cli /home/dcarlier/Contribs/php-src/sapi/cli/php_cli.c:964
#13 0x5565af535877 in main /home/dcarlier/Contribs/php-src/sapi/cli/php_cli.c:1334
#14 0x7faf6c633d67 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
#15 0x7faf6c633e24 in __libc_start_main_impl ../csu/libc-start.c:360
#16 0x5565adc04040 in _start (/home/dcarlier/Contribs/php-src/sapi/cli/php+0x2604040) (BuildId: 949049955bdf8b7197390b1978a1dfc3ef6fdf38)
AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: FPE nptl/pthread_kill.c:44 in __pthread_kill_implementation
==286922==ABORTING
```
close phpGH-16384
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