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[NFC] Finalize blocks with explicit breakability in IRBuilder #7085

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Nov 18, 2024
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[NFC] Finalize blocks with explicit breakability in IRBuilder #7085

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[NFC] Finalize blocks with explicit breakability in IRBuilder
tlively Nov 16, 2024
3981163
Merge branch 'main' into ir-builder-breakability
tlively Nov 18, 2024
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tlively Nov 18, 2024
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7 changes: 7 additions & 0 deletions src/passes/Outlining.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -304,6 +304,13 @@ struct Outlining : public Pass {
// Position the outlined functions first in the functions vector to make
// the outlining lit tests far more readable.
moveOutlinedFunctions(module, substrings.size());

// Because we visit control flow in an odd order, IRBuilder is not able to
// properly track branches, so it may not have finalized blocks with the
// correct types. ReFinalize now to fix any issues.
PassRunner runner(getPassRunner());
runner.add(std::make_unique<ReFinalize>());
runner.run();
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This comment sort of suggests to me that Outlining should not be using IRBuilder...? What does "an odd order" mean?

lgtm otherwise

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Outlining visits control flow expressions in a breadth-first order rather than doing a normal postorder traversal. So it visits every top-level expression in a function body, ends the function, then visits the contents of every block it saw while traversing those top-level expressions, etc. Another way to look at it is that Outlining uses IRBuilder to build one control flow structure at a time rather than a whole function at at a time.

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This "odd" traversal should be well documented in passes/stringify-walker.h.

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Ok, sounds good. Maybe add a link to there?

}

Name addOutlinedFunction(Module* module,
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12 changes: 8 additions & 4 deletions src/wasm/wasm-ir-builder.cpp
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Expand Up @@ -972,7 +972,12 @@ Result<> IRBuilder::visitEnd() {
block->type = blockType;
return block;
}
return builder.makeBlock(label, {curr}, blockType);
auto* block = builder.makeBlock();
block->name = label;
block->list.push_back(curr);
block->finalize(blockType,
scope.labelUsed ? Block::HasBreak : Block::NoBreak);
return block;
};

if (auto* func = scope.getFunction()) {
Expand All @@ -985,9 +990,8 @@ Result<> IRBuilder::visitEnd() {
} else if (auto* block = scope.getBlock()) {
assert(*expr == block);
block->name = scope.label;
// TODO: Track branches so we can know whether this block is a target and
// finalize more efficiently.
block->finalize(block->type);
block->finalize(block->type,
scope.labelUsed ? Block::HasBreak : Block::NoBreak);
push(block);
} else if (auto* loop = scope.getLoop()) {
loop->body = *expr;
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