Coro: Remove coro_end and coro_suspend_retcon in private unprocessed functions

[aschwaighofer]

Summary

We might emit functions that are private and never called. The coro
split pass only processes functions that might be called. Remove
intrinsics that we can't generate code for.

rdar://84619859

llvm/lib/Transforms/Coroutines/CoroCleanup.cpp

static void lowerSubFn(IRBuilder<> &Builder, CoroSubFnInst *SubFn) {
   auto *Load = Builder.CreateLoad(FrameTy->getElementType(Index), Gep);
 
   SubFn->replaceAllUsesWith(Load);
 }
 
 bool Lowerer::lowerRemainingCoroIntrinsics(Function &F) {
   bool Changed = false;
 
+  bool IsPrivateAndUnprocessed =
+      F.hasFnAttribute(CORO_PRESPLIT_ATTR) && F.hasLocalLinkage();
+
   for (Instruction &I : llvm::make_early_inc_range(instructions(F))) {
     if (auto *II = dyn_cast<IntrinsicInst>(&I)) {
       switch (II->getIntrinsicID()) {
       default:
         continue;
       case Intrinsic::coro_begin:
         II->replaceAllUsesWith(II->getArgOperand(1));
         break;
if (auto *II = dyn_cast<IntrinsicInst>(&I)) {
       case Intrinsic::coro_id_retcon:
       case Intrinsic::coro_id_retcon_once:
       case Intrinsic::coro_id_async:
         II->replaceAllUsesWith(ConstantTokenNone::get(Context));
         break;
       case Intrinsic::coro_subfn_addr:
         lowerSubFn(Builder, cast<CoroSubFnInst>(II));
         break;
+      case Intrinsic::coro_end:
+      case Intrinsic::coro_suspend_retcon:
+        if (IsPrivateAndUnprocessed) {
+          II->replaceAllUsesWith(UndefValue::get(II->getType()));
+        } else
+          continue;
+        break;
       case Intrinsic::coro_async_size_replace:
         auto *Target = cast<ConstantStruct>(
             cast<GlobalVariable>(II->getArgOperand(0)->stripPointerCasts())
                 ->getInitializer());
         auto *Source = cast<ConstantStruct>(
             cast<GlobalVariable>(II->getArgOperand(1)->stripPointerCasts())
                 ->getInitializer());
         auto *TargetSize = Target->getOperand(1);

llvm/test/Transforms/Coroutines/coro-retcon-once-private.ll

+; RUN: opt < %s -enable-coroutines -passes='default<O0>' -S | FileCheck %s
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.12.0"
+
+; CHECK: define internal { i8*, i32 } @f(i8* %buffer, i32* %array)
+; CHECK-NEXT: entry:
+; CHECK-NEXT:  unreachable
+
+define internal {i8*, i32} @f(i8* %buffer, i32* %array) {
+entry:
+  %id = call token @llvm.coro.id.retcon.once(i32 8, i32 8, i8* %buffer, i8* bitcast (void (i8*, i1)* @prototype to i8*), i8* bitcast (i8* (i32)* @allocate to i8*), i8* bitcast (void (i8*)* @deallocate to i8*))
+  %hdl = call i8* @llvm.coro.begin(token %id, i8* null)
+  %load = load i32, i32* %array
+  %load.pos = icmp sgt i32 %load, 0
+  br i1 %load.pos, label %pos, label %neg
+
+pos:
+  %unwind0 = call i1 (...) @llvm.coro.suspend.retcon.i1(i32 %load)
+  br i1 %unwind0, label %cleanup, label %pos.cont
+
+pos.cont:
+  store i32 0, i32* %array, align 4
+  br label %cleanup
+
+neg:
+  %unwind1 = call i1 (...) @llvm.coro.suspend.retcon.i1(i32 0)
+  br i1 %unwind1, label %cleanup, label %neg.cont
+
+neg.cont:
+  store i32 10, i32* %array, align 4
+  br label %cleanup
+
+cleanup:
+  call i1 @llvm.coro.end(i8* %hdl, i1 0)
+  unreachable
+}
+
+declare token @llvm.coro.id.retcon.once(i32, i32, i8*, i8*, i8*, i8*)
+declare i8* @llvm.coro.begin(token, i8*)
+declare i1 @llvm.coro.suspend.retcon.i1(...)
+declare i1 @llvm.coro.end(i8*, i1)
+declare i8* @llvm.coro.prepare.retcon(i8*)
+
+declare void @prototype(i8*, i1 zeroext)
+
+declare noalias i8* @allocate(i32 %size)
+declare void @deallocate(i8* %ptr)