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ConstraintAnalysis: Fix some trivial asserts #8893

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Merged
kripken merged 3 commits into from
Jul 10, 2026
+64 −8
Merged

ConstraintAnalysis: Fix some trivial asserts #8893

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9c8f060
ConstraintAnalysis: Do not apply constraints in unreachable code
kripken Jul 10, 2026
d9456a3
ConstraintAnalysis: Fix assertion on trivial info
kripken Jul 10, 2026
dd212ec
Update test/lit/passes/constraint-analysis.wast
kripken Jul 10, 2026
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6 changes: 1 addition & 5 deletions src/ir/constraint.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -288,11 +288,7 @@ void BasicBlockConstraintMap::set(Index index, const Constraint& c) {

// Clear the old state.
eraseStaleRefs(index);
map[index].setProvesNothing();
// Note that this last line puts us in a temporarily invalid state: we do not
// normally store a constraint of proves-nothing in the map. Doing it this
// way, until approximateAnd adds the constraint, is more efficient than
// erasing and re-adding.
map.erase(index);

// Apply the constraint.
approximateAnd(index, c);
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8 changes: 5 additions & 3 deletions src/passes/ConstraintAnalysis.cpp
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Expand Up @@ -187,12 +187,14 @@ struct ConstraintAnalysis
// of course not needed at this stage.)
auto& constraints = block->contents.startConstraints;
for (auto** currp : block->contents.actions) {
applyToConstraints(*currp, constraints);
if (constraints.unreachable) {
if (!constraints.unreachable) {
applyToConstraints(*currp, constraints);
optimizeExpression(currp, constraints);
} else {
// This is unreachable code: just mark it so.
*currp = Builder(*getModule()).makeUnreachable();
refinalize = true;
}
optimizeExpression(currp, constraints);
}
}

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58 changes: 58 additions & 0 deletions test/lit/passes/constraint-analysis.wast
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Expand Up @@ -3472,4 +3472,62 @@
(br $loop)
)
)

;; CHECK: (func $unreachable-loop (type $1)
;; CHECK-NEXT: (local $x i32)
;; CHECK-NEXT: (unreachable)
;; CHECK-NEXT: (unreachable)
;; CHECK-NEXT: )
;; OPTIN: (func $unreachable-loop (type $1)
;; OPTIN-NEXT: (local $x i32)
;; OPTIN-NEXT: (unreachable)
;; OPTIN-NEXT: (unreachable)
;; OPTIN-NEXT: )
(func $unreachable-loop
(local $x i32)
;; The entire loop is unreachable. The control flow here should not cause any
;; internal errors, and we can just optimize this to unreachable.
(unreachable)
(local.set $x
(loop $loop (result i32)
(i32.const 0)
)
)
)

;; CHECK: (func $set-silly (type $0) (param $x i32)
;; CHECK-NEXT: (local.set $x
;; CHECK-NEXT: (local.get $x)
;; CHECK-NEXT: )
;; CHECK-NEXT: (if
;; CHECK-NEXT: (i32.const 0)
;; CHECK-NEXT: (then
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; OPTIN: (func $set-silly (type $0) (param $x i32)
;; OPTIN-NEXT: (local.set $x
;; OPTIN-NEXT: (local.get $x)
;; OPTIN-NEXT: )
;; OPTIN-NEXT: (if
;; OPTIN-NEXT: (i32.const 0)
;; OPTIN-NEXT: (then
;; OPTIN-NEXT: )
;; OPTIN-NEXT: )
;; OPTIN-NEXT: )
(func $set-silly (param $x i32)
;; Setting x to x adds no information, and we do not store it in the IR. This
;; must not lead to internal errors (we have asserts on not storing
;; "proves-nothing" in the internal map, and if we wrote this, it would be
;; that).
(local.set $x
(local.get $x)
)
;; Add some control flow to exercise the assert.
(if
(i32.const 0)
(then)
)
)
)

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