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StripObjectHeaders: make sure that a dealloc_ref comes from the original root allocation.

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Fixes a miscompile
This commit is contained in:
Erik Eckstein
2023-09-19 11:12:18 +02:00
parent 5bc036661c
commit 614a635d5d
1 changed files with 14 additions and 3 deletions
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17
SwiftCompilerSources/Sources/Optimizer/FunctionPasses/StripObjectHeaders.swift
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@@ -37,13 +37,15 @@ let stripObjectHeadersPass = FunctionPass(name: "strip-object-headers") {
private extension Value {
func needObjectHeader() -> Bool {
var walker = IsBareObjectWalker()
var walker = IsBareObjectWalker(rootDef: self)
return walker.walkDownUses(ofValue: self, path: SmallProjectionPath()) == .abortWalk
}
}
private struct IsBareObjectWalker : ValueDefUseWalker {
private struct IsBareObjectWalker : ValueDefUseWalker, ValueUseDefWalker {
var walkUpCache = WalkerCache<SmallProjectionPath>()
var walkDownCache = WalkerCache<SmallProjectionPath>()
let rootDef: Value
mutating func walkDown(value operand: Operand, path: Path) -> WalkResult {
switch operand.instruction {
@@ -67,11 +69,20 @@ private struct IsBareObjectWalker : ValueDefUseWalker {
switch operand.instruction {
// White-list all instructions which don't use the object header.
case is RefElementAddrInst, is RefTailAddrInst,
is DeallocRefInst, is DeallocStackRefInst,
is DeallocStackRefInst,
is DebugValueInst, is FixLifetimeInst:
return .continueWalk
case let deallocRef as DeallocRefInst:
// Check if the final dealloc_ref comes from the single `rootDef`.
// In case of phi-arguments it might come from multiple root definitions.
return walkUp(value: deallocRef.operand.value, path: path)
default:
return .abortWalk
}
}
mutating func rootDef(value: Value, path: SmallProjectionPath) -> WalkResult {
return value == rootDef ? .continueWalk : .abortWalk
}
}