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archived-php-src/Zend/zend_vm_execute.skl
Arnaud Le Blanc 73b98a3858 TAILCALL VM
Introduce the TAILCALL VM, a more efficient variant of the CALL VM:

 * Each opcode handler tailcalls the next opcode handler directly instead of
   returning to the interpreter loop. This eliminates call and interpreter loop
   overhead.
 * Opcode handlers use the preserve_none calling convention to eliminate
   register saving overhead.
 * preserve_none uses non-volatile registers for its first arguments, so
   execute_data and opline are usually kept in these registers and no code is
   required to forward them to the next handlers.

Generated machine code is similar to a direct-threaded VM with register pinning,
like the HYBRID VM.

JIT+TAILCALL VM also benefits from this compared to JIT+CALL VM:

 * JIT uses the registers of the execute_data and opline args as fixed regs,
   eliminating the need to move them in prologue.
 * Traces exit by tailcalling the next handler. No code is needed to forward
   execute_data and opline.
 * No register saving/restoring in epilogue/prologue.

The TAILCALL VM is used when the HYBRID VM is not supported, and the compiler
supports the musttail and preserve_none attributes: The HYBRID VM is used when
compiling with GCC, the TAILCALL VM when compiling with Clang>=19 on x86_64 or
aarch64, and the CALL VM otherwise.

This makes binaries built with Clang>=19 as fast as binaries built with GCC.
Before, these were considerably slower (by 2.8% to 44% depending on benchmark,
and by 5% to 77% before 76d7c616bb).

Closes GH-17849
Closes GH-18720
2025-08-22 18:05:52 +02:00

168 lines
4.3 KiB
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#include "Zend/zend_vm_opcodes.h"
{%DEFINES%}
#if (ZEND_VM_KIND != ZEND_VM_KIND_CALL) && (ZEND_GCC_VERSION >= 4000) && !defined(__clang__)
# pragma GCC push_options
# pragma GCC optimize("no-gcse")
# pragma GCC optimize("no-ivopts")
#endif
#if defined(_WIN64) && defined(_M_X64)
/* See save_xmm_x86_64_ms_masm.asm */
void {%EXECUTOR_NAME%}_ex_real(zend_execute_data *ex)
#else
ZEND_API void {%EXECUTOR_NAME%}_ex(zend_execute_data *ex)
#endif
{
DCL_OPLINE
#if defined(__GNUC__) && defined(__aarch64__)
__asm__ __volatile__ (""::: "v8","v9","v10","v11","v12","v13","v14","v15");
#endif
{%HELPER_VARS%}
{%INTERNAL_LABELS%}
LOAD_OPLINE();
ZEND_VM_LOOP_INTERRUPT_CHECK();
#ifdef ZEND_CHECK_STACK_LIMIT
if (UNEXPECTED(zend_call_stack_overflowed(EG(stack_limit)))) {
zend_call_stack_size_error();
/* No opline was executed before exception */
EG(opline_before_exception) = NULL;
LOAD_OPLINE();
/* Fall through to handle exception below. */
}
#endif /* ZEND_CHECK_STACK_LIMIT */
while (1) {
{%ZEND_VM_CONTINUE_LABEL%}
{%ZEND_VM_DISPATCH%} {
{%INTERNAL_EXECUTOR%}
}
}
zend_error_noreturn(E_CORE_ERROR, "Arrived at end of main loop which shouldn't happen");
}
#if (ZEND_VM_KIND != ZEND_VM_KIND_CALL) && (ZEND_GCC_VERSION >= 4000) && !defined(__clang__)
# pragma GCC pop_options
#endif
ZEND_API void zend_{%EXECUTOR_NAME%}(zend_op_array *op_array, zval *return_value)
{
zend_execute_data *execute_data;
void *object_or_called_scope;
uint32_t call_info;
if (EG(exception) != NULL) {
return;
}
object_or_called_scope = zend_get_this_object(EG(current_execute_data));
if (EXPECTED(!object_or_called_scope)) {
object_or_called_scope = zend_get_called_scope(EG(current_execute_data));
call_info = ZEND_CALL_TOP_CODE | ZEND_CALL_HAS_SYMBOL_TABLE;
} else {
call_info = ZEND_CALL_TOP_CODE | ZEND_CALL_HAS_SYMBOL_TABLE | ZEND_CALL_HAS_THIS;
}
execute_data = zend_vm_stack_push_call_frame(call_info,
(zend_function*)op_array, 0, object_or_called_scope);
if (EG(current_execute_data)) {
execute_data->symbol_table = zend_rebuild_symbol_table();
} else {
execute_data->symbol_table = &EG(symbol_table);
}
EX(prev_execute_data) = EG(current_execute_data);
i_init_code_execute_data(execute_data, op_array, return_value);
ZEND_OBSERVER_FCALL_BEGIN(execute_data);
zend_{%EXECUTOR_NAME%}_ex(execute_data);
/* Observer end handlers are called from ZEND_RETURN */
zend_vm_stack_free_call_frame(execute_data);
}
{%EXTERNAL_EXECUTOR%}
void {%INITIALIZER_NAME%}(void)
{
{%EXTERNAL_LABELS%}
VM_TRACE_START();
}
static HashTable *zend_handlers_table = NULL;
void zend_vm_dtor(void)
{
VM_TRACE_END();
if (zend_handlers_table) {
zend_hash_destroy(zend_handlers_table);
free(zend_handlers_table);
zend_handlers_table = NULL;
}
}
static void init_opcode_serialiser(void)
{
int i;
zval tmp;
zend_handlers_table = malloc(sizeof(HashTable));
zend_hash_init(zend_handlers_table, zend_handlers_count, NULL, NULL, 1);
zend_hash_real_init(zend_handlers_table, 0);
Z_TYPE_INFO(tmp) = IS_LONG;
for (i = 0; i < zend_handlers_count; i++) {
Z_LVAL(tmp) = i;
zend_hash_index_add(zend_handlers_table, (zend_long)(uintptr_t)zend_opcode_handlers[i], &tmp);
}
}
ZEND_API void ZEND_FASTCALL zend_serialize_opcode_handler(zend_op *op)
{
zval *zv;
if (!zend_handlers_table) {
init_opcode_serialiser();
}
zv = zend_hash_index_find(zend_handlers_table, (zend_long)(uintptr_t)op->handler);
ZEND_ASSERT(zv != NULL);
op->handler = (zend_vm_opcode_handler_t)(uintptr_t)Z_LVAL_P(zv);
}
ZEND_API void ZEND_FASTCALL zend_deserialize_opcode_handler(zend_op *op)
{
op->handler = zend_opcode_handlers[(uintptr_t)op->handler];
}
ZEND_API const void* ZEND_FASTCALL zend_get_opcode_handler_func(const zend_op *op)
{
#if ZEND_VM_KIND == ZEND_VM_KIND_HYBRID || ZEND_VM_KIND == ZEND_VM_KIND_TAILCALL
zval *zv;
if (!zend_handlers_table) {
init_opcode_serialiser();
}
zv = zend_hash_index_find(zend_handlers_table, (zend_long)(uintptr_t)op->handler);
ZEND_ASSERT(zv != NULL);
return zend_opcode_handler_funcs[Z_LVAL_P(zv)];
#elif ZEND_VM_KIND == ZEND_VM_KIND_CALL
return op->handler;
#else
return NULL;
#endif
}
ZEND_API const zend_op *zend_get_halt_op(void)
{
#if ZEND_VM_KIND == ZEND_VM_KIND_HYBRID
return &hybrid_halt_op;
#else
return NULL;
#endif
}
ZEND_API int zend_vm_kind(void)
{
return ZEND_VM_KIND;
}