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Fix a bug with unreachable control flow in IRBuilder #6130

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Merged
tlively merged 1 commit into from
Nov 21, 2023
Merged

Fix a bug with unreachable control flow in IRBuilder #6130

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1 change: 1 addition & 0 deletions src/wasm-ir-builder.h
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Original file line number Diff line number Diff line change
Expand Up @@ -238,6 +238,7 @@ class IRBuilder : public UnifiedExpressionVisitor<IRBuilder, Result<>> {

// The branch label name for this scope. Always fresh, never shadowed.
Name label;
bool labelUsed = false;

std::vector<Expression*> exprStack;
// Whether we have seen an unreachable instruction and are in
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12 changes: 10 additions & 2 deletions src/wasm/wasm-ir-builder.cpp
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Expand Up @@ -570,10 +570,17 @@ Result<> IRBuilder::visitEnd() {
CHECK_ERR(expr);

// If the scope expression cannot be directly labeled, we may need to wrap it
// in a block.
// in a block. It's possible that the scope expression becomes typed
// unreachable when it is finalized, but if the wrapper block is targeted by
// any branches, the target block needs to have the original non-unreachable
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@ashleynh ashleynh Nov 21, 2023

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Why does the target block need to have the original non-unreachable type of the scope expression?

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@ashleynh ashleynh Nov 21, 2023

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Talked offline.

// type of the scope expression.
auto originalScopeType = scope.getResultType();
auto maybeWrapForLabel = [&](Expression* curr) -> Expression* {
if (scope.label) {
return builder.makeBlock(scope.label, {curr}, scope.getResultType());
return builder.makeBlock(scope.label,
{curr},
scope.labelUsed ? originalScopeType
: scope.getResultType());
}
return curr;
};
Expand Down Expand Up @@ -624,6 +631,7 @@ Result<Name> IRBuilder::getLabelName(Index label) {
// The scope does not already have a name, so we need to create one.
scopeLabel = makeFresh("label");
}
(*scope)->labelUsed = true;
return scopeLabel;
}

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44 changes: 43 additions & 1 deletion test/lit/wat-kitchen-sink.wast
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Expand Up @@ -1257,6 +1257,48 @@
end
)

;; CHECK: (func $if-else-brs (type $void)
;; CHECK-NEXT: (block $label
;; CHECK-NEXT: (if
;; CHECK-NEXT: (i32.const 0)
;; CHECK-NEXT: (br $label)
;; CHECK-NEXT: (br $label)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
(func $if-else-brs
i32.const 0
if
br 0
else
br 0
end
)

;; CHECK: (func $if-else-brs-i32 (type $1) (result i32)
;; CHECK-NEXT: (block $label (result i32)
;; CHECK-NEXT: (if (result i32)
;; CHECK-NEXT: (i32.const 0)
;; CHECK-NEXT: (br $label
;; CHECK-NEXT: (i32.const 1)
;; CHECK-NEXT: )
;; CHECK-NEXT: (br $label
;; CHECK-NEXT: (i32.const 2)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
(func $if-else-brs-i32 (result i32)
i32.const 0
if (result i32)
i32.const 1
br 0
else
i32.const 2
br 0
end
)

;; CHECK: (func $loop (type $void)
;; CHECK-NEXT: (loop
;; CHECK-NEXT: (nop)
Expand Down Expand Up @@ -2332,7 +2374,7 @@
(func $ref-func
ref.func $ref-func
drop
ref.func 107
ref.func 109
drop
)

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