Add J2CL optimization pass to binaryen. #6151
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This PR creates a new pass to optimize J2CL specific patterns that would otherwise difficult to recognize/prove generically by other binaryen passes. The pass currently handles fields what we call as "constant-like". These fields are fields initialized once and unconditionally through "clinit" function and technically they do have 2 observable states; - initial null/0 state - initialized state. However you can only observe initial null/0 state in contrived examples, not in real world/correct applications. This pass moves such "clinit" initialized fields to global initialization. Above pattern also matches other lazy init construct like String and Class literals (which binaryen already reduces to constant expressions). So the pass is generalized to include them as well. (by matching any functions with the name pattern "_@once_") In order for this pass to be effective: 1. It needs to run between O3 passes 2. We need to stop inlining of "once" functions. Stopping inlining of the once functions are important to preseve their structure. This both helps existing OnceReducer pass and new J2CL pass to be a lot more effective. Also it is not useful to inline these functions as by defintion they only executed once. This could be achieved by passing no-inline filter. Although the inlining is generally disabled for these functions, it is still needed for some cases since inliner is effectively responsible for removal of the once functions that are simplified into empty or simple delegating functions. For this reason, the pass will rename such trivial function so no-inline filter will no longer match them. Also note that after all optimizations completed, it does make sense to have a final stage where the "partial inline" of all once functions are allowed. This will speed them up by moving the initialization check to call-site.
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@kripken Again pardon my C++; I'm not familiar with best practices and guidelines so you can assume I don't know what I'm doing and comment accordingly. I will send the tests in follow up commits within same PR. |
src/passes/J2clOpts.cpp
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| if (!GlobalUtils::canInitializeGlobal(*getModule(), set->value)) { | ||
| // It is not a valid constant expression so cannot be hoisted to | ||
| // global init. |
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It is convenient that this rules out all the dangerous situations, like local state, doing a call, etc.
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Exactly, it was nicely fit!
Are there some instructions that I can follow to add the tests? |
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For testing, you can add a file in parallel to this one: https://github.com/WebAssembly/binaryen/blob/main/test/lit/passes/inlining_splitting_basics.wast The name can be the same as the commandline flag to run the pass. To test it locally for quick iteration, you can run (or whatever the filename ends up being). That adds the expected results in the file. |
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You will also need to run |
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@kripken Some of the expected results are put in weird places like: I'm not sure what I'm doing wrong. |
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I've seen it move expected outputs around when it doesn't find the corresponding input. Are those functions at the end new ones created by split inlining or such? That could explain it. Anyhow, it's probably not something wrong that you are doing, but I can take a closer look when the tests are added. |
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Oh I see. That's probably due to the renaming of the methods then (to enable inlining). I will stop doing that so should be fine. |
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PTAL @kripken |
Co-authored-by: Alon Zakai <alonzakai@gmail.com>
Co-authored-by: Alon Zakai <alonzakai@gmail.com>
Co-authored-by: Alon Zakai <alonzakai@gmail.com>
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I tihnk it is good to go now. |
This PR creates a new pass to optimize J2CL specific patterns that would otherwise difficult to recognize/prove generically by other binaryen passes. The pass currently handles fields what we call as "constant-like". These fields are fields initialized once and unconditionally through "clinit" function and technically they do have 2 observable states; - initial null/0 state - initialized state. However you can only observe initial null/0 state in contrived examples, not in real world/correct applications. This pass moves such "clinit" initialized fields to global initialization. Above pattern also matches other lazy init construct like String and Class literals (which binaryen already reduces to constant expressions). So the pass is generalized to include them as well. (by matching any functions with the name pattern "_@once_") In order for this pass to be effective: 1. It needs to run between O3 passes 2. We need to stop inlining of "once" functions. Stopping inlining of the once functions are important to preserve their structure. This both helps existing OnceReducer pass and new J2CL pass to be a lot more effective. Also it is not useful to inline these functions as by defintion they only executed once. This could be achieved by passing no-inline filter. Although the inlining is generally disabled for these functions, it is still needed for some cases since inliner is effectively responsible for removal of the once functions that are simplified into empty or simple delegating functions. For this reason, the pass will rename such trivial function so no-inline filter will no longer match them. Also note that after all optimizations completed, it does make sense to have a final stage where the "partial inline" of all once functions are allowed. This will speed them up by moving the initialization check to call-site.
This PR creates a new pass to optimize J2CL specific patterns that would otherwise difficult to recognize/prove generically by other binaryen passes.
The pass currently handles fields what we call as "constant-like". These fields are fields initialized once and unconditionally through "clinit" function and technically they do have 2 observable states;
This pass moves such "clinit" initialized fields to global initialization.
Above pattern also matches other lazy init construct like String and Class literals (which binaryen already reduces to constant expressions). So the pass is generalized to include them as well. (by matching any functions with the name pattern
_@once_)In order for this pass to be effective:
Stopping inlining of the once functions are important to preseve their structure. This both helps existing OnceReducer pass and new J2CL pass to be a lot more effective. Also it is not useful to inline these functions as by defintion they only executed once. This could be achieved by passing no-inline filter.
Although the inlining is generally disabled for these functions, it is still needed for some cases since inliner is effectively responsible for removal of the once functions that are simplified into empty or simple delegating functions. For this reason, the pass will rename such trivial function so no-inline filter will no longer match them.
Also note that after all optimizations completed, it does make sense to have a final stage where the "partial inline" of all once functions are allowed. This will speed them up by moving the initialization check to call-site.