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A comment on How many registers does an x86-64 CPU have? (2020). Parent comment

Re:How many registers does an x86-64 CPU have? (2020) by guenthert on Sunday February 15, 2026 @07:48AM (#47023267)
> It's up to the compiler to decide how many registers it needs to preserve at a call.

But the compiler is bound by the ABI, isn't it? (at least for externally visible entrance points / calls to sub routines external to the current compilation unit)

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Re:How many registers does an x86-64 CPU have? (2020) by cvoss on Sunday February 15, 2026 @01:43PM (#47026209)
Someone decides how to define the ABI too, and that is a free choice. CPU register count doesn't constrain this particular system design question.
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