Store long-lived toplevel values into globals #30
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We could generate invalid code for `Obj.set_field x 0 (Obj.repr f)` in `Lazy.from_fun` (OCaml 4.14) when `f` is a known function.
number of instructions after being defined is stored into a global instead of a local. The goals are the following: - Turn a large number of closures into constant closures, which has a significant impact on performance - Reduce the compilation time of the toplevel function in case the Wasm engine decide to optimize it: reduce the register pressure by avoiding long-lived registers in the toplevel function, and make load elimination less expensive by reducing the number of constant structures defined in this function.
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So if I understand correctly, after this pass no function will use more than 1,000 locals? |
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This is only for the toplevel function. And we are counting 1000 instructions in the intermediate code, not in the generated code. So this does not put an exact limit on the number of locals. And wasm-opt might not be able to coalesce some variables since it has refined their types. |
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I see. |
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Any variable which is used a number of instructions after being defined is stored into a global
instead of a local. The goals are the following:
This also improves binaryen's compilation time.