[llvm] [AMDGPU] Propagate alias information in AMDGPULowerKernelArguments. (PR #161375)

[Leon Clark via llvm-commits]

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@@ -58,6 +66,143 @@ static BasicBlock::iterator getInsertPt(BasicBlock &BB) {
   return InsPt;
 }
 
+static void addAliasScopeMetadata(Function &F, DataLayout const &DL) {
+  // Collect noalias arguments.
+  auto NoAliasArgs = SmallVector<Argument const *, 4u>();
+
+  for (auto &Arg : F.args())
+    if (Arg.hasNoAliasAttr() && !Arg.use_empty())
+      NoAliasArgs.push_back(&Arg);
+
+  if (NoAliasArgs.empty())
+    return;
+
+  // Add alias scopes for each noalias argument.
+  auto MDB = MDBuilder(F.getContext());
+  auto NewScopes = DenseMap<Argument const *, MDNode *>();
+  auto *NewDomain = MDB.createAnonymousAliasScopeDomain(F.getName());
+
+  for (auto I = 0u; I < NoAliasArgs.size(); ++I) {
+    auto *Arg = NoAliasArgs[I];
+    auto Name = std::string(F.getName());
+
+    if (Arg->hasName())
+      Name += std::string(": %") + std::string(Arg->getName());
+    else
+      Name += std::string(": argument ") + std::to_string(I);
+
+    auto *NewScope = MDB.createAnonymousAliasScope(NewDomain, Name);
+    NewScopes.insert(std::make_pair(Arg, NewScope));
+  }
+
+  // Iterate over all instructions.
+  auto DT = DominatorTree();
+  DT.recalculate(F);
+
+  for (auto Inst = inst_begin(F); Inst != inst_end(F); ++Inst) {
----------------
PeddleSpam wrote:

We could recursively look at the uses of each `noalias` argument, but we'd need to use a set to make sure we don't collect the same instructions multiple times, and we'd probably end up collecting most of the instructions anyway.

https://github.com/llvm/llvm-project/pull/161375