[llvm] [Attributor] Pack out arguments into a struct (PR #119267)

[Matt Arsenault via llvm-commits]

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@@ -2963,6 +2963,132 @@ bool Attributor::shouldSeedAttribute(AbstractAttribute &AA) {
   return Result;
 }
 
+// For now: argument can be put in the struct if it's write only and
+// has no aliases.
+static bool canBeComapctedInAStruct(const Argument &Arg, Attributor &A,
+                                    const AbstractAttribute &QueryingAA) {
+  IRPosition ArgPosition = IRPosition::argument(Arg);
+  // Check if Arg has no alias.
+  auto *AAliasInfo =
+      A.getAAFor<AANoAlias>(QueryingAA, ArgPosition, DepClassTy::NONE);
+  if (!AAliasInfo || !AAliasInfo->isKnownNoAlias())
+    return false;
+
+  // Check if Arg is write-only.
+  const auto *MemBehaviorAA =
+      A.getAAFor<AAMemoryBehavior>(QueryingAA, ArgPosition, DepClassTy::NONE);
+  if (!MemBehaviorAA || !MemBehaviorAA->isKnownWriteOnly())
+    return false;
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arsenm wrote:

Need negative tests for every condition 

https://github.com/llvm/llvm-project/pull/119267