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by joelangeway
4307 days ago
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Even if a JIT compiler can prove that all the code in your app doesn't change that function pointer, because the variable is volatile, the compiler must assume that you intend to read from actual metal every time you refer to it and it can not predict what the value will be. Even a JIT compiler is not allowed to optimize away that read, or else you'd never be able to write a driver. |
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Because a JIT may have enough knowledge of the underlying system to know that the pointer is not pointing to a memory-mapped / DMA'd / etc area, and as such can be assumed to remain constant.