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Ban address phis in non-OSSA SIL

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Meghana Gupta
2022-09-12 11:12:16 -07:00
parent d5f6b12830
commit 035f062e69
1 changed files with 1 additions and 19 deletions
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20
lib/SIL/Verifier/SILVerifier.cpp
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@@ -985,24 +985,6 @@ public:
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.
@@ -1026,7 +1008,7 @@ public:
"All phi argument inputs must be from branches.");
}
}
if (arg->isPhi() && prohibitAddressPhis()) {
if (arg->isPhi()) {
// 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