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Merged
tlively merged 2 commits into from
Apr 19, 2023
Merged

Disable sign extension in SignExtLowering.cpp #5676

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01b126f
Disable sign extension in SignExtLowering.cpp
tlively Apr 19, 2023
ed169c8
update pass description
tlively Apr 19, 2023
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8 changes: 8 additions & 0 deletions src/passes/SignExtLowering.cpp
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Expand Up @@ -68,6 +68,14 @@ struct SignExtLowering : public WalkerPass<PostWalker<SignExtLowering>> {
}
}
}

void run(Module* module) override {
if (!module->features.has(FeatureSet::SignExt)) {

@sbc100 sbc100 Apr 19, 2023

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Is it possible the module could contain sign ext instructions but this feature not be enabled? (I guess in that case it would not validate?)

@sbc100 sbc100 Apr 19, 2023

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I also wonder why the test we have in emscripten for this was passing.. investigating.

@sbc100 sbc100 Apr 19, 2023

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The emscripten test merely checks that --signext-lowering is part of the wasm-opt command line .. I didn't both to actually decompile the module to verify binaryen was actually doing the right thing.

@tlively tlively Apr 19, 2023

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Is it possible the module could contain sign ext instructions but this feature not be enabled? (I guess in that case it would not validate?)

Right, in this case the module would not validate and Binaryen would produce an error.

return;
}
super::run(module);
module->features.disable(FeatureSet::SignExt);
}
};

Pass* createSignExtLoweringPass() { return new SignExtLowering(); }
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3 changes: 2 additions & 1 deletion src/passes/pass.cpp
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Expand Up @@ -408,7 +408,8 @@ void PassRegistry::registerPasses() {
"apply more specific subtypes to signature types where possible",
createSignatureRefiningPass);
registerPass("signext-lowering",
"lower sign-ext operations to wasm mvp",
"lower sign-ext operations to wasm mvp and disable the sign "
"extension feature",
createSignExtLoweringPass);
registerPass("simplify-globals",
"miscellaneous globals-related optimizations",
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3 changes: 2 additions & 1 deletion test/lit/help/wasm-opt.test
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Expand Up @@ -399,7 +399,8 @@
;; CHECK-NEXT: signature types where possible
;; CHECK-NEXT:
;; CHECK-NEXT: --signext-lowering lower sign-ext operations to
;; CHECK-NEXT: wasm mvp
;; CHECK-NEXT: wasm mvp and disable the sign
;; CHECK-NEXT: extension feature
;; CHECK-NEXT:
;; CHECK-NEXT: --simplify-globals miscellaneous globals-related
;; CHECK-NEXT: optimizations
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3 changes: 2 additions & 1 deletion test/lit/help/wasm2js.test
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Expand Up @@ -358,7 +358,8 @@
;; CHECK-NEXT: signature types where possible
;; CHECK-NEXT:
;; CHECK-NEXT: --signext-lowering lower sign-ext operations to
;; CHECK-NEXT: wasm mvp
;; CHECK-NEXT: wasm mvp and disable the sign
;; CHECK-NEXT: extension feature
;; CHECK-NEXT:
;; CHECK-NEXT: --simplify-globals miscellaneous globals-related
;; CHECK-NEXT: optimizations
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9 changes: 9 additions & 0 deletions test/lit/passes/signext-lowering-features.wast
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@@ -0,0 +1,9 @@
;; RUN: wasm-opt %s --enable-sign-ext --print-features --print --signext-lowering --print-features | filecheck %s

;; Check that the --signext-lowering pass disables the signext feature.

;; CHECK: --enable-sign-ext
;; CHECK: (module
;; CHECK-NOT: --enable-sign-ext

(module)