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GH-138245: Perform boolean guards by testing a single bit, rather than a full pointer comparison. #143810

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@markshannon markshannon commented Jan 13, 2026 •
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This reduces the overhead of performing boolean guards in jitted code.

On Aarch64 reduces the size of the stencil from 5 to 2 instructions.

GUARD_IS_FALSE_POP_r10:

 adrp x8, 0x0 // _Py_FalseStruct
 ldr x8, [x8] // _Py_FalseStruct
 orr x8, x8, #0x1
 cmp x24, x8
 b.ne jump_target

_GUARD_BIT_IS_SET_POP_4_r10:

 tbnz w24, #0x4, next
 b jump_target
next:
 // 0000000000000004: R_AARCH64_JUMP26 _JIT_JUMP_TARGET

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