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OptimizeInstructions: Fix max bits of a local with an unreachable set #7623

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Merged
merged 1 commit into from
May 27, 2025
Merged

OptimizeInstructions: Fix max bits of a local with an unreachable set #7623

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1 change: 1 addition & 0 deletions src/passes/OptimizeInstructions.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -129,6 +129,7 @@ struct LocalScanner : PostWalker<LocalScanner> {
Properties::getFallthrough(curr->value, passOptions, *getModule());
auto& info = localInfo[curr->index];
info.maxBits = std::max(info.maxBits, Bits::getMaxBits(value, this));
info.maxBits = std::min(info.maxBits, getBitsForType(type));
auto signExtBits = LocalInfo::kUnknown;
if (Properties::getSignExtValue(value)) {
signExtBits = Properties::getSignExtBits(value);
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37 changes: 37 additions & 0 deletions test/lit/passes/optimize-instructions-mvp.wast
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Expand Up @@ -18410,4 +18410,41 @@
)
)
)

;; CHECK: (func $local-unreachable-size-matters
;; CHECK-NEXT: (local $temp i32)
;; CHECK-NEXT: (local.set $temp
;; CHECK-NEXT: (i32.const 1)
;; CHECK-NEXT: )
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (i32.and
;; CHECK-NEXT: (local.get $temp)
;; CHECK-NEXT: (i32.const 1)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: (local.tee $temp
;; CHECK-NEXT: (unreachable)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
(func $local-unreachable-size-matters
;; The local is written 1, then later down we have an unreachable. That
;; should not confuse us as to the max bits in the local. This is a test for
;; a bug where any local with an unreachable set got assigned 64 bits, which
;; is wrong in this case and led to a misoptimization of the |and|. We
;; should not optimize it away to a 0 (we could in theory optimize it to a
;; 1, but this pass does not infer locals that precisely).
(local $temp i32)
(local.set $temp
(i32.const 1)
)
(drop
(i32.and
(local.get $temp)
(i32.const 1)
)
)
(local.tee $temp
(unreachable)
)
)
)
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