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A comment on TIL: Go's CompareAndSwap is not always Compare-and-swap.

Re:TIL: Go's CompareAndSwap is not always Compare-and-swap by perryizgr8 on Monday January 08, 2024 @05:37PM (#38919320)
// Check support for LSE atomics

MOVBU internal∕cpu·ARM64+const_offsetARM64HasATOMICS(SB), R4

CBZ R4, load_store_loop

Why is this a runtime decision? Shouldn't the compiler know if the target machine supports the instruction or not?

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Re:TIL: Go's CompareAndSwap is not always Compare-and-swap by enz on Monday January 08, 2024 @05:59PM (#38919619)
I believe Go wants to support "ARM64" that just works among the heterogeneous fleets of Arm machines (from Raspberry Pi to Graviton EC2 instances) and let the programmer not to worry about it. GCC seems to do the same if I believe the article linked on "MySQL on ARM": it emits code that dynamically decides to either use CAS or LL/SC depending on the LSE support.
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