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Revert "Ban address phis in non-OSSA as well" #61018

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Merged
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Sep 9, 2022
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Revert "Ban address phis in non-OSSA as well" #61018

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20 changes: 19 additions & 1 deletion lib/SIL/Verifier/SILVerifier.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -985,6 +985,24 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
return InstNumbers[a] < InstNumbers[b];
}

// FIXME: For sanity, address-type phis should be prohibited at all SIL
// stages. However, the optimizer currently breaks the invariant in three
// places:
// 1. Normal Simplify CFG during conditional branch simplification
// (sneaky jump threading).
// 2. Simplify CFG via Jump Threading.
// 3. Loop Rotation.
//
// BasicBlockCloner::canCloneInstruction and sinkAddressProjections is
// designed to avoid this issue, we just need to make sure all passes use it
// correctly.
//
// Minimally, we must prevent address-type phis as long as access markers are
// preserved. A goal is to preserve access markers in OSSA.
bool prohibitAddressPhis() {
return F.hasOwnership();
}

void visitSILPhiArgument(SILPhiArgument *arg) {
// Verify that the `isPhiArgument` property is sound:
// - Phi arguments come from branches.
Expand All @@ -1008,7 +1026,7 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
"All phi argument inputs must be from branches.");
}
}
if (arg->isPhi()) {
if (arg->isPhi() && prohibitAddressPhis()) {
// As a property of well-formed SIL, we disallow address-type
// phis. Supporting them would prevent reliably reasoning about the
// underlying storage of memory access. This reasoning is important for
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