[llvm] Attributor: Infer noalias.addrspace metadata for memory instructions (PR #136553)

[Matt Arsenault via llvm-commits]

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@@ -12780,6 +12781,214 @@ struct AAAddressSpaceCallSiteArgument final : AAAddressSpaceImpl {
 };
 } // namespace
 
+/// ------------------------ No Alias Address Space  ---------------------------
+namespace {
+struct AANoAliasAddrSpaceImpl : public AANoAliasAddrSpace {
+  AANoAliasAddrSpaceImpl(const IRPosition &IRP, Attributor &A)
+      : AANoAliasAddrSpace(IRP, A) {}
+
+  void initialize(Attributor &A) override {
+    assert(getAssociatedType()->isPtrOrPtrVectorTy() &&
+           "Associated value is not a pointer");
+
+    if (!A.getInfoCache().getFlatAddressSpace().has_value()) {
+      resetASRanges(A);
+      indicatePessimisticFixpoint();
+      return;
+    }
+
+    unsigned FlatAS = A.getInfoCache().getFlatAddressSpace().value();
+    resetASRanges(A);
+    removeAS(FlatAS);
+
+    unsigned AS = getAssociatedType()->getPointerAddressSpace();
+    if (AS != FlatAS) {
+      removeAS(AS);
+      indicateOptimisticFixpoint();
+    }
+  }
+
+  ChangeStatus updateImpl(Attributor &A) override {
+    unsigned FlatAS = A.getInfoCache().getFlatAddressSpace().value();
+    uint32_t OrigAssumed = getAssumed();
+
+    auto CheckAddressSpace = [&](Value &Obj) {
+      if (isa<PoisonValue>(&Obj))
+        return true;
+      // Handle argument in flat address space only has addrspace cast uses
+      if (auto *Arg = dyn_cast<Argument>(&Obj)) {
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arsenm wrote:

This isn't specifically checking kernels but I would avoid trying to handle the flat kernel argument hack in the first attempt at this 

https://github.com/llvm/llvm-project/pull/136553