[llvm] [IPO] Added attributor for identifying invariant loads (PR #141800)

[Shilei Tian via llvm-commits]

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@@ -12534,6 +12535,301 @@ struct AAIndirectCallInfoCallSite : public AAIndirectCallInfo {
 };
 } // namespace
 
+/// --------------------- Invariant Load Pointer -------------------------------
+namespace {
+
+struct AAInvariantLoadPointerImpl
+    : public StateWrapper<BitIntegerState<uint8_t, 15>,
+                          AAInvariantLoadPointer> {
+
+  enum {
+    // pointer does not alias within the bounds of the function
+    IS_NOALIAS = 1 << 0,
+    // pointer is not involved in any effectful instructions within the bounds
+    // of the function
+    IS_NOEFFECT = 1 << 1,
+    // loads are invariant within the bounds of the function
+    IS_LOCALLY_INVARIANT = 1 << 2,
+    // memory lifetime is constrained within the bounds of the function
+    IS_LOCALLY_CONSTRAINED = 1 << 3,
+
+    IS_BEST_STATE = IS_NOALIAS | IS_NOEFFECT | IS_LOCALLY_INVARIANT |
+                    IS_LOCALLY_CONSTRAINED,
+  };
+  static_assert(getBestState() == IS_BEST_STATE, "Unexpected best state");
+
+  using Base =
+      StateWrapper<BitIntegerState<uint8_t, 15>, AAInvariantLoadPointer>;
+
+  // the BitIntegerState is optimistic about IS_NOALIAS and IS_NOEFFECT, but
+  // pessimistic about IS_KNOWN_INVARIANT
+  AAInvariantLoadPointerImpl(const IRPosition &IRP, Attributor &A)
+      : Base(IRP) {}
+
+  bool isKnownInvariant() const final {
+    return isKnownLocallyInvariant() && isKnown(IS_LOCALLY_CONSTRAINED);
+  }
+  bool isKnownLocallyInvariant() const final {
+    if (isKnown(IS_LOCALLY_INVARIANT))
+      return true;
+    return isKnown(IS_NOALIAS | IS_NOEFFECT);
+  }
+
+  bool isAssumedInvariant() const final {
+    return isAssumedLocallyInvariant() && isAssumed(IS_LOCALLY_CONSTRAINED);
+  }
+  bool isAssumedLocallyInvariant() const final {
+    if (isAssumed(IS_LOCALLY_INVARIANT))
+      return true;
+    return isAssumed(IS_NOALIAS | IS_NOEFFECT);
+  }
+
+  ChangeStatus updateImpl(Attributor &A) override {
+    if (isKnownInvariant())
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shiltian wrote:

Move this to the end

https://github.com/llvm/llvm-project/pull/141800