Do not emit lifetime intrinsics for coro promise alloca

Author: NewSigma

clang/lib/CodeGen/CGDecl.cpp

@@ -1343,6 +1343,11 @@ llvm::Value *CodeGenFunction::EmitLifetimeStart(llvm::TypeSize Size,
   if (!ShouldEmitLifetimeMarkers)
     return nullptr;
 
+  // No lifetimes on promise alloca, or middle end passes will assume promise
+  // dead after lifetime.end, leading to mis-optimization
+  if (Addr->getName() == "__promise")
+    return nullptr;
+
   assert(Addr->getType()->getPointerAddressSpace() ==
              CGM.getDataLayout().getAllocaAddrSpace() &&
          "Pointer should be in alloca address space");

clang/test/CodeGenCoroutines/coro-params.cpp

@@ -84,7 +84,6 @@ void f(int val, MoveOnly moParam, MoveAndCopy mcParam, TrivialABI trivialParam)
   // 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: call void @_ZN10TrivialABIC1EOS_(ptr {{[^,]*}} %[[TrivialCopy]], ptr {{[^,]*}} %[[TrivialAlloca]])
-  // CHECK-NEXT: call void @llvm.lifetime.start.p0(
   // CHECK-NEXT: invoke void @_ZNSt16coroutine_traitsIJvi8MoveOnly11MoveAndCopy10TrivialABIEE12promise_typeC1Ev(
 
   // CHECK: call void @_ZN14suspend_always12await_resumeEv(
@@ -106,7 +105,6 @@ void f(int val, MoveOnly moParam, MoveAndCopy mcParam, TrivialABI trivialParam)
 
   // Destroy promise, then parameter copies:
   // 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]])
@@ -135,7 +133,6 @@ void dependent_params(T x, U, U y) {
   // CHECK-NEXT: call void @_ZN1BC1EOS_(ptr {{[^,]*}} %[[unnamed_copy]], ptr noundef nonnull align 4 dereferenceable(512) %0)
   // CHECK-NEXT: call void @llvm.lifetime.start.p0(
   // CHECK-NEXT: call void @_ZN1BC1EOS_(ptr {{[^,]*}} %[[y_copy]], ptr noundef nonnull align 4 dereferenceable(512) %y)
-  // CHECK-NEXT: call void @llvm.lifetime.start.p0(
   // CHECK-NEXT: invoke void @_ZNSt16coroutine_traitsIJv1A1BS1_EE12promise_typeC1Ev(
 
   co_return;

clang/test/CodeGenCoroutines/coro-suspend-cleanups.cpp

@@ -52,7 +52,7 @@ coroutine ArrayInitCoro() {
     // CHECK-NEXT:  store ptr %arrayinit.element, ptr %arrayinit.endOfInit.reload.addr, align 8
     co_await Awaiter{}
     // CHECK-NEXT:  @_ZNSt14suspend_always11await_readyEv
-    // CHECK-NEXT:  br i1 %{{.+}}, label %await.ready, label %CoroSave30
+    // CHECK-NEXT:  br i1 %{{.+}}, label %await.ready, label %CoroSave29
   };
   // CHECK:       await.cleanup:                                    ; preds = %AfterCoroSuspend{{.*}}
   // CHECK-NEXT:    br label %cleanup{{.*}}.from.await.cleanup