[Coroutines] Mark parameter allocas with coro.outside.frame metadata

Parameters to a coroutine get copied (moved) to coroutine-local
instances which code inside the coroutine then uses.

The original parameters should not be part of the frame. Normally
CoroSplit figures that out by itself, but for [[clang::trivial_abi]]
parameters which, get destructed at the end of the ramp function,
it does not (see bug), causing use-after-free's if the frame is
destroyed before the end of the ramp (as happens if it doesn't suspend).

Since Clang knows these should never be part of the frame, use metadata
to make it so.

Fixes #127499

Author: zmodem

clang/lib/CodeGen/CGCoroutine.cpp

@@ -855,6 +855,16 @@ void CodeGenFunction::EmitCoroutineBody(const CoroutineBodyStmt &S) {
     // Create parameter copies. We do it before creating a promise, since an
     // evolution of coroutine TS may allow promise constructor to observe
     // parameter copies.
+    for (const ParmVarDecl *Parm : FnArgs) {
+      // If the original param is in an alloca, exclude it from the coroutine
+      // frame. The parameter copy will be part of the frame.
+      Address ParmAddr = GetAddrOfLocalVar(Parm);
+      if (auto *ParmAlloca =
+              dyn_cast<llvm::AllocaInst>(ParmAddr.getBasePointer())) {
+        ParmAlloca->setMetadata(llvm::LLVMContext::MD_coro_outside_frame,
+                                llvm::MDNode::get(CGM.getLLVMContext(), {}));
+      }
+    }
     for (auto *PM : S.getParamMoves()) {
       EmitStmt(PM);
       ParamReplacer.addCopy(cast<DeclStmt>(PM));

clang/test/CodeGenCoroutines/coro-params.cpp

@@ -59,46 +59,67 @@ struct MoveAndCopy {
   ~MoveAndCopy();
 };
 
-void consume(int,int,int) noexcept;
+struct [[clang::trivial_abi]] TrivialABI {
+  int val;
+  TrivialABI(MoveAndCopy&&) noexcept;
+  ~TrivialABI();
+};
+
+void consume(int,int,int,int) noexcept;
 
 // TODO: Add support for CopyOnly params
-// CHECK: define{{.*}} void @_Z1fi8MoveOnly11MoveAndCopy(i32 noundef %val, ptr noundef %[[MoParam:.+]], ptr noundef %[[McParam:.+]]) #0 personality ptr @__gxx_personality_v0
-void f(int val, MoveOnly moParam, MoveAndCopy mcParam) {
+// CHECK: define{{.*}} void @_Z1fi8MoveOnly11MoveAndCopy10TrivialABI(i32 noundef %val, ptr noundef %[[MoParam:.+]], ptr noundef %[[McParam:.+]], i32 %[[TrivialParam:.+]]) #0 personality ptr @__gxx_personality_v0
+void f(int val, MoveOnly moParam, MoveAndCopy mcParam, TrivialABI trivialParam) {
+  // CHECK: %[[TrivialAlloca:.+]] = alloca %struct.TrivialABI,
+  // CHECK-SAME: !coro.outside.frame
   // CHECK: %[[MoCopy:.+]] = alloca %struct.MoveOnly,
   // CHECK: %[[McCopy:.+]] = alloca %struct.MoveAndCopy,
+  // CHECK: %[[TrivialCopy:.+]] = alloca %struct.TrivialABI,
   // CHECK: store i32 %val, ptr %[[ValAddr:.+]]
 
   // CHECK: call ptr @llvm.coro.begin(
   // CHECK: call void @_ZN8MoveOnlyC1EOS_(ptr {{[^,]*}} %[[MoCopy]], ptr noundef nonnull align 4 dereferenceable(4) %[[MoParam]])
   // CHECK-NEXT: call void @llvm.lifetime.start.p0(
   // CHECK-NEXT: call void @_ZN11MoveAndCopyC1EOS_(ptr {{[^,]*}} %[[McCopy]], ptr noundef nonnull align 4 dereferenceable(4) %[[McParam]]) #
   // CHECK-NEXT: call void @llvm.lifetime.start.p0(
-  // CHECK-NEXT: invoke void @_ZNSt16coroutine_traitsIJvi8MoveOnly11MoveAndCopyEE12promise_typeC1Ev(
+  // CHECK-NEXT: call void @llvm.memcpy
+  // CHECK-SAME: %[[TrivialCopy]]
+  // CHECK-SAME: %[[TrivialAlloca]]
+  // CHECK-NEXT: call void @llvm.lifetime.start.p0(
+  // CHECK-NEXT: invoke void @_ZNSt16coroutine_traitsIJvi8MoveOnly11MoveAndCopy10TrivialABIEE12promise_typeC1Ev(
 
   // CHECK: call void @_ZN14suspend_always12await_resumeEv(
   // CHECK: %[[IntParam:.+]] = load i32, ptr %{{.*}}
   // CHECK: %[[MoGep:.+]] = getelementptr inbounds nuw %struct.MoveOnly, ptr %[[MoCopy]], i32 0, i32 0
   // CHECK: %[[MoVal:.+]] = load i32, ptr %[[MoGep]]
-  // CHECK: %[[McGep:.+]] =  getelementptr inbounds nuw %struct.MoveAndCopy, ptr %[[McCopy]], i32 0, i32 0
+  // CHECK: %[[McGep:.+]] = getelementptr inbounds nuw %struct.MoveAndCopy, ptr %[[McCopy]], i32 0, i32 0
   // CHECK: %[[McVal:.+]] = load i32, ptr %[[McGep]]
-  // CHECK: call void @_Z7consumeiii(i32 noundef %[[IntParam]], i32 noundef %[[MoVal]], i32 noundef %[[McVal]])
+  // CHECK: %[[TrivialGep:.+]] = getelementptr inbounds nuw %struct.TrivialABI, ptr %[[TrivialCopy]], i32 0, i32 0
+  // CHECK: %[[TrivialVal:.+]] = load i32, ptr %[[TrivialGep]]
+  // CHECK: call void @_Z7consumeiiii(i32 noundef %[[IntParam]], i32 noundef %[[MoVal]], i32 noundef %[[McVal]], i32 noundef %[[TrivialVal]])
 
-  consume(val, moParam.val, mcParam.val);
+  consume(val, moParam.val, mcParam.val, trivialParam.val);
   co_return;
 
   // Skip to final suspend:
-  // CHECK: call void @_ZNSt16coroutine_traitsIJvi8MoveOnly11MoveAndCopyEE12promise_type13final_suspendEv(
+  // CHECK: call void @_ZNSt16coroutine_traitsIJvi8MoveOnly11MoveAndCopy10TrivialABIEE12promise_type13final_suspendEv(
   // CHECK: call void @_ZN14suspend_always12await_resumeEv(
 
   // Destroy promise, then parameter copies:
-  // CHECK: call void @_ZNSt16coroutine_traitsIJvi8MoveOnly11MoveAndCopyEE12promise_typeD1Ev(ptr {{[^,]*}} %__promise)
+  // CHECK: call void @_ZNSt16coroutine_traitsIJvi8MoveOnly11MoveAndCopy10TrivialABIEE12promise_typeD1Ev(ptr {{[^,]*}} %__promise)
+  // CHECK-NEXT: call void @llvm.lifetime.end.p0(
+  // CHECK-NEXT: call void @_ZN10TrivialABID1Ev(ptr {{[^,]*}} %[[TrivialCopy]])
   // CHECK-NEXT: call void @llvm.lifetime.end.p0(
   // CHECK-NEXT: call void @_ZN11MoveAndCopyD1Ev(ptr {{[^,]*}} %[[McCopy]])
   // CHECK-NEXT: call void @llvm.lifetime.end.p0(
   // CHECK-NEXT: call void @_ZN8MoveOnlyD1Ev(ptr {{[^,]*}} %[[MoCopy]]
   // CHECK-NEXT: call void @llvm.lifetime.end.p0(
   // CHECK-NEXT: call void @llvm.lifetime.end.p0(
   // CHECK-NEXT: call ptr @llvm.coro.free(
+
+  // The original trivial_abi parameter is destroyed when returning from the ramp.
+  // CHECK: call i1 @llvm.coro.end
+  // CHECK: call void @_ZN10TrivialABID1Ev(ptr {{[^,]*}} %[[TrivialAlloca]])
 }
 
 // CHECK-LABEL: void @_Z16dependent_paramsI1A1BEvT_T0_S3_(ptr noundef %x, ptr noundef %0, ptr noundef %y)