TAILLCALL VM: Do not return in ZEND_VM_ENTER_EX, ZEND_VM_LEAVE#21475
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arnaud-lb wants to merge 3 commits intophp:masterfrom
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TAILLCALL VM: Do not return in ZEND_VM_ENTER_EX, ZEND_VM_LEAVE#21475arnaud-lb wants to merge 3 commits intophp:masterfrom
arnaud-lb wants to merge 3 commits intophp:masterfrom
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dstogov
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Mar 23, 2026
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As I understood, this affects only TAILCALL VM.
So, it should be fine, except for a single minor comment.
Zend/zend_vm_gen.php
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| out($f," } while (0)\n"); | ||
| out($f,"# define ZEND_VM_DISPATCH_TO_LEAVE_HELPER(helper) opline = &call_leave_op; SAVE_OPLINE(); ZEND_VM_CONTINUE()\n"); | ||
| out($f,"# define ZEND_VM_INTERRUPT() ZEND_VM_TAIL_CALL(zend_interrupt_helper".($spec?"_SPEC":"")."_TAILCALL(ZEND_OPCODE_HANDLER_ARGS_PASSTHRU))\n"); | ||
| out($f,"# define ZEND_VM_ENTER_EX() ZEND_VM_CONTINUE()\n"); |
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This misses ZEND_VM_INTERRUPT_CHECK();, otherwise a deeply recursive function couldn't be interrupted.
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Thank you, I forgot about this. In the CALL VM, ZEND_VM_ENTER_EX() relies on the interpreter loop to check for interrupts. Here we need to check interrupts in ZEND_VM_ENTER_EX() since we don't return to the loop anymore.
I've added ZEND_VM_INTERRUPT_CHECK(). Performance numbers are not impacted meaningfully.
dstogov
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Mar 23, 2026
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The TAILLCALL VM returns in ZEND_VM_ENTER_EX and ZEND_VM_LEAVE, but that's not necessary.
Redefine ZEND_VM_ENTER_EX, ZEND_VM_LEAVE so that they tailcall instead.
This makes the Symfony and bench.php benchmarks about 1% and 3.5% faster.