Index: llvm/lib/Transforms/Coroutines/CoroFrame.cpp
===================================================================
--- llvm/lib/Transforms/Coroutines/CoroFrame.cpp
+++ llvm/lib/Transforms/Coroutines/CoroFrame.cpp
@@ -2333,14 +2333,16 @@
                                      SuspendCrossingInfo &Checker) {
   DominatorTree DT(F);
 
-  // Collect all possible basic blocks which may dominate all uses of allocas.
+  // Collect all possible basic blocks which may dominate all uses of allocas
+  // except the entry block.
   SmallPtrSet<BasicBlock *, 4> DomSet;
-  DomSet.insert(&F.getEntryBlock());
   for (auto *CSI : Shape.CoroSuspends) {
     BasicBlock *SuspendBlock = CSI->getParent();
     assert(isSuspendBlock(SuspendBlock) && SuspendBlock->getSingleSuccessor() &&
            "should have split coro.suspend into its own block");
-    DomSet.insert(SuspendBlock->getSingleSuccessor());
+    BasicBlock *SwitchBlock = SuspendBlock->getSingleSuccessor();
+    for (auto *BB : llvm::successors(SwitchBlock))
+      DomSet.insert(BB);
   }
 
   for (Instruction &I : instructions(F)) {
@@ -2391,18 +2393,17 @@
       // Sink lifetime.start markers to dominate block when they are
       // only used outside the region.
       if (Valid && Lifetimes.size() != 0) {
-        // May be AI itself, when the type of AI is i8*
-        auto *NewBitCast = [&](AllocaInst *AI) -> Value* {
-          if (isa<AllocaInst>(Lifetimes[0]->getOperand(1)))
-            return AI;
-          auto *Int8PtrTy = Type::getInt8PtrTy(F.getContext());
-          return CastInst::Create(Instruction::BitCast, AI, Int8PtrTy, "",
-                                  DomBB->getTerminator());
-        }(AI);
-
         auto *NewLifetime = Lifetimes[0]->clone();
-        NewLifetime->replaceUsesOfWith(NewLifetime->getOperand(1), NewBitCast);
-        NewLifetime->insertBefore(DomBB->getTerminator());
+        if (isa<AllocaInst>(NewLifetime->getOperand(1)))
+          NewLifetime->insertBefore(DomBB->getFirstNonPHI());
+        else {
+          auto *NewBitCast = CastInst::Create(
+              Instruction::BitCast, AI, Type::getInt8PtrTy(F.getContext()), "",
+              DomBB->getFirstNonPHI());
+          NewLifetime->replaceUsesOfWith(NewLifetime->getOperand(1),
+                                         NewBitCast);
+          NewLifetime->insertAfter(NewBitCast);
+        }
 
         // All the outsided lifetime.start markers are no longer necessary.
         for (Instruction *S : Lifetimes)
Index: llvm/test/Transforms/Coroutines/coro-split-musttail4.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/Coroutines/coro-split-musttail4.ll
@@ -0,0 +1,68 @@
+; Tests that sink lifetime doesn't affect musttail.
+; RUN: opt < %s -coro-split -S | FileCheck %s
+; RUN: opt < %s -passes=coro-split -S | FileCheck %s
+
+declare void @fakeresume1(i8*)
+
+declare void @fakeresume2(i64* align 8)
+
+define void @g() #0 {
+entry:
+  %id = call token @llvm.coro.id(i32 0, i8* null, i8* null, i8* null)
+  %alloc = call i8* @malloc(i64 16) #3
+  %alloc.var = alloca i8
+  call void @llvm.lifetime.start.p0i8(i64 1, i8* %alloc.var)
+  %vFrame = call noalias nonnull i8* @llvm.coro.begin(token %id, i8* %alloc)
+
+  %save = call token @llvm.coro.save(i8* null)
+  %suspend = call i8 @llvm.coro.suspend(token %save, i1 false)
+  call fastcc void @fakeresume1(i8* null)
+  switch i8 %suspend, label %exit [
+    i8 0, label %await.suspend
+    i8 1, label %exit
+  ]
+await.suspend:
+  %save2 = call token @llvm.coro.save(i8* null)
+  call fastcc void @fakeresume2(i64* align 8 null)
+  %suspend2 = call i8 @llvm.coro.suspend(token %save2, i1 false)
+  switch i8 %suspend2, label %exit [
+    i8 0, label %await.ready
+    i8 1, label %exit
+  ]
+await.ready:
+  call void @consume(i8* %alloc.var)
+  call void @llvm.lifetime.end.p0i8(i64 1, i8* %alloc.var)
+  br label %exit
+exit:
+  call i1 @llvm.coro.end(i8* null, i1 false)
+  ret void
+}
+
+; Verify that in the initial function resume is not marked with musttail.
+; CHECK-LABEL: @g(
+; CHECK-NOT: musttail call fastcc void @fakeresume1(i8* null)
+
+; Verify that in the resume part resume call is marked with musttail.
+; CHECK-LABEL: @g.resume(
+; CHECK: musttail call fastcc void @fakeresume2(i64* align 8 null)
+; CHECK-NEXT: ret void
+
+declare token @llvm.coro.id(i32, i8* readnone, i8* nocapture readonly, i8*) #1
+declare i1 @llvm.coro.alloc(token) #2
+declare i64 @llvm.coro.size.i64() #3
+declare i8* @llvm.coro.begin(token, i8* writeonly) #2
+declare token @llvm.coro.save(i8*) #2
+declare i8* @llvm.coro.frame() #3
+declare i8 @llvm.coro.suspend(token, i1) #2
+declare i8* @llvm.coro.free(token, i8* nocapture readonly) #1
+declare i1 @llvm.coro.end(i8*, i1) #2
+declare i8* @llvm.coro.subfn.addr(i8* nocapture readonly, i8) #1
+declare i8* @malloc(i64)
+declare void @consume(i8*)
+declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture)
+declare void @llvm.lifetime.end.p0i8(i64, i8* nocapture)
+
+attributes #0 = { "coroutine.presplit"="1" }
+attributes #1 = { argmemonly nounwind readonly }
+attributes #2 = { nounwind }
+attributes #3 = { nounwind readnone }