[llvm] [IPO] Added attributor for identifying invariant loads (PR #141800)
Shilei Tian via llvm-commits
llvm-commits at lists.llvm.org
Wed May 28 10:07:17 PDT 2025
================
@@ -12534,6 +12535,248 @@ struct AAIndirectCallInfoCallSite : public AAIndirectCallInfo {
};
} // namespace
+/// --------------------- Invariant Load Pointer -------------------------------
+namespace {
+
+struct AAInvariantLoadPointerImpl
+ : public StateWrapper<BitIntegerState<uint8_t, 7>, AAInvariantLoadPointer,
+ uint8_t> {
+ // load invariance is implied by, but not equivalent to IS_NOALIAS |
+ // IS_READONLY, as load invariance is also implied by all underlying objects
+ // being load invariant.
+ //
+ // IS_INVARIANT is set to indicate that the contents of the pointer are
+ // *known* to be invariant.
+ enum {
+ IS_INVARIANT = 1 << 0,
+ IS_NOALIAS = 1 << 1,
+ IS_READONLY = 1 << 2,
+ };
+ static_assert(getBestState() == (IS_INVARIANT | IS_NOALIAS | IS_READONLY),
+ "Unexpected best state!");
+
+ using Base = StateWrapper<BitIntegerState<uint8_t, 7>, AAInvariantLoadPointer,
+ uint8_t>;
+
+ // the BitIntegerState is optimistic about noalias and readonly, but
+ // pessimistic about invariance
+ AAInvariantLoadPointerImpl(const IRPosition &IRP, Attributor &A)
+ : Base(IRP, IS_NOALIAS | IS_READONLY) {}
+
+ void initialize(Attributor &A) final {
+ // conservatively assume that the pointer's contents are not invariant,
+ // until proven otherwise.
+ removeAssumedBits(IS_INVARIANT);
+ }
+
+ bool isKnownInvariant() const final {
+ return isKnown(IS_INVARIANT) || isKnown(IS_NOALIAS | IS_READONLY);
+ }
+
+ bool isAssumedInvariant() const final {
+ return isAssumed(IS_INVARIANT) || isAssumed(IS_NOALIAS | IS_READONLY);
+ }
+
+ ChangeStatus updateImpl(Attributor &A) override {
+ if (isKnownInvariant())
+ return ChangeStatus::UNCHANGED;
----------------
shiltian wrote:
indicate optimistic state here
https://github.com/llvm/llvm-project/pull/141800
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