[llvm-branch-commits] [llvm] [LLVM][Coroutines] Create `.noalloc` variant of switch ABI coroutine ramp functions during CoroSplit (PR #99283)

[Adrian Vogelsgesang via llvm-branch-commits]

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@@ -1455,6 +1462,64 @@ struct SwitchCoroutineSplitter {
     setCoroInfo(F, Shape, Clones);
   }
 
+  static Function *createNoAllocVariant(Function &F, coro::Shape &Shape,
+                                        SmallVectorImpl<Function *> &Clones) {
+    auto *OrigFnTy = F.getFunctionType();
+    auto OldParams = OrigFnTy->params();
+
+    SmallVector<Type *> NewParams;
+    NewParams.reserve(OldParams.size() + 1);
+    for (Type *T : OldParams) {
+      NewParams.push_back(T);
+    }
+    NewParams.push_back(PointerType::getUnqual(Shape.FrameTy));
+
+    auto *NewFnTy = FunctionType::get(OrigFnTy->getReturnType(), NewParams,
+                                      OrigFnTy->isVarArg());
+    Function *NoAllocF =
+        Function::Create(NewFnTy, F.getLinkage(), F.getName() + ".noalloc");
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vogelsgesang wrote:

I wonder if the function should be marked as `linkage = internal`. To my understanding, the `[[coro_must_elide]]` does not work across translation units, yet. As such, there won't be any cross-TU calls to the `.noalloc` function

https://github.com/llvm/llvm-project/pull/99283