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Optimize spread operator for packed arrays (fix GH-9794) #9796

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Merged
merged 2 commits into from
Oct 26, 2022
Merged

Optimize spread operator for packed arrays (fix GH-9794) #9796

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f5cc5f6
optimize spread operator for packed arrays
jhdxr Oct 21, 2022
106207d
ci fix
jhdxr Oct 21, 2022
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46 changes: 31 additions & 15 deletions Zend/zend_vm_def.h
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Original file line number Diff line number Diff line change
Expand Up @@ -6047,23 +6047,39 @@ ZEND_VM_C_LABEL(add_unpack_again):
if (EXPECTED(Z_TYPE_P(op1) == IS_ARRAY)) {
HashTable *ht = Z_ARRVAL_P(op1);
zval *val;
zend_string *key;

if (HT_IS_PACKED(ht) && (zend_hash_num_elements(result_ht) == 0 || HT_IS_PACKED(result_ht))) {
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@TysonAndre TysonAndre Oct 22, 2022 •
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Suggested change
if (HT_IS_PACKED(ht) && (zend_hash_num_elements(result_ht) == 0 || HT_IS_PACKED(result_ht))) {
if (HT_IS_PACKED(ht) && (!HT_IS_INITIALIZED(result_ht) || HT_IS_PACKED(result_ht))) {

I'm pretty sure there can be hash tables that are initialized but associative(not packed), e.g. $globalXyz = ['a' => 'val']; unset($globalXyz['a']); has zend_hash_num_elements === 0

  1. oh, right, this is a temporary array being constructed and only being added to, that suggestion isn't technically needed here, but I expect my suggestion to be be faster anyway since both macros are checking HT_FLAGS from the same location in memory and the compiler could optimize that
  2. HT_IS_INITIALIZED is a better example for other code and I'd personally strongly recommend that

Seems like it should behave correctly

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Yeah this is just to check if the temp array needs to be mark as packed and/or extend to necessary size. zend_hash_num_elements is for new array.

I'll do a benchmark later to see there is any performance improvement, although I won't expect much difference. zend_hash_num_elements is inline and simple.

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since both macros are checking HT_FLAGS from the same location in memory and the compiler could optimize that

And following up, unsurprisingly, the compiler does optimize that (one less branch to predict, so I'd expect it to be better, though for it to be that noticeable you'd use a random mix of lists of length 0 and 1)

https://godbolt.org/z/sdaPEf8z9

void xyz(int n) {
    if ((n & (1<<2)) || !(n&(1<<3))) {
        puts("Matches one flag and not the other");
    }
}

e.g. the condition compiles to (x&12) != 8

        and     edi, 12
        cmp     edi, 8
        jne     .LBB0_2

zend_hash_extend(result_ht, zend_hash_num_elements(result_ht) + zend_hash_num_elements(ht), 1);
ZEND_HASH_FILL_PACKED(result_ht) {
ZEND_HASH_PACKED_FOREACH_VAL(ht, val) {
if (UNEXPECTED(Z_ISREF_P(val)) &&
UNEXPECTED(Z_REFCOUNT_P(val) == 1)) {
val = Z_REFVAL_P(val);
}
Z_TRY_ADDREF_P(val);
ZEND_HASH_FILL_ADD(val);
} ZEND_HASH_FOREACH_END();
} ZEND_HASH_FILL_END();
} else {
zend_string *key;

ZEND_HASH_FOREACH_STR_KEY_VAL(ht, key, val) {
if (Z_ISREF_P(val) && Z_REFCOUNT_P(val) == 1) {
val = Z_REFVAL_P(val);
}
Z_TRY_ADDREF_P(val);
if (key) {
zend_hash_update(result_ht, key, val);
} else {
if (!zend_hash_next_index_insert(result_ht, val)) {
zend_cannot_add_element();
zval_ptr_dtor_nogc(val);
break;
ZEND_HASH_FOREACH_STR_KEY_VAL(ht, key, val) {
if (UNEXPECTED(Z_ISREF_P(val)) &&
UNEXPECTED(Z_REFCOUNT_P(val) == 1)) {
val = Z_REFVAL_P(val);
}
}
} ZEND_HASH_FOREACH_END();
Z_TRY_ADDREF_P(val);
if (key) {
zend_hash_update(result_ht, key, val);
} else {
if (!zend_hash_next_index_insert(result_ht, val)) {
zend_cannot_add_element();
zval_ptr_dtor_nogc(val);
break;
}
}
} ZEND_HASH_FOREACH_END();
}
} else if (EXPECTED(Z_TYPE_P(op1) == IS_OBJECT)) {
zend_class_entry *ce = Z_OBJCE_P(op1);
zend_object_iterator *iter;
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46 changes: 31 additions & 15 deletions Zend/zend_vm_execute.h
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