Index: llvm/lib/CodeGen/CodeGenPrepare.cpp
===================================================================
--- llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -2485,8 +2485,24 @@
       Value *IncomingVal = PN->getIncomingValue(I)->stripPointerCasts();
       CallInst *CI = dyn_cast<CallInst>(IncomingVal);
       BasicBlock *PredBB = PN->getIncomingBlock(I);
+
+      // LLVM treats calls that return one of their arguments as casts, and
+      // forwardoring/looking through that may split a tail call from the value
+      // it returns even more than a phi. Attempt to undo this by looking for a
+      // suitable call in the phi's predecessor block.
+      if (!CI) {
+        BranchInst *BI = dyn_cast<BranchInst>(PredBB->getTerminator());
+        if (!BI || !BI->isUnconditional())
+          continue;
+        CallInst *CastCI =
+            dyn_cast_or_null<CallInst>(BI->getPrevNonDebugInstruction());
+        if (!CastCI || CastCI->getReturnedArgOperand() != IncomingVal)
+          continue;
+        CI = CastCI;
+      }
+
       // Make sure the phi value is indeed produced by the tail call.
-      if (CI && CI->hasOneUse() && CI->getParent() == PredBB &&
+      if (CI && CI->getParent() == PredBB &&
           TLI->mayBeEmittedAsTailCall(CI) &&
           attributesPermitTailCall(F, CI, RetI, *TLI))
         TailCallBBs.push_back(PredBB);
Index: llvm/test/CodeGen/AArch64/tailcall-returned.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AArch64/tailcall-returned.ll
@@ -0,0 +1,61 @@
+; RUN: opt --codegenprepare -mtriple=arm64-apple-macosx %s -S -o - | FileCheck %s
+
+define ptr @test_already_opt(ptr %in, i1 %tst) {
+; CHECK-LABEL: @test_already_opt
+  br i1 %tst, label %true, label %false
+
+true:
+; CHECK: tail call ptr @return_input(ptr %in)
+; CHECK-NEXT: ret ptr %in
+
+  %call = tail call ptr @return_input(ptr %in)
+  br label %done
+
+false:
+  br label %done
+
+done:
+  %res = phi ptr [ %in, %true ],  [ null, %false ]
+  ret ptr %res
+}
+
+define ptr @test_simple(ptr %in, i1 %tst) {
+; CHECK-LABEL: @test_simple
+  br i1 %tst, label %true, label %false
+
+true:
+; CHECK: tail call ptr @return_input(ptr %in)
+; CHECK-NEXT: ret ptr %call
+
+  %call = tail call ptr @return_input(ptr %in)
+  br label %done
+
+false:
+  br label %done
+
+done:
+  %res = phi ptr [ %call, %true ],  [ null, %false ]
+  ret ptr %res
+}
+
+define ptr @test_unsafe(ptr %in, i1 %tst) {
+; CHECK-LABEL: @test_unsafe
+  br i1 %tst, label %true, label %false
+
+true:
+; CHECK: tail call ptr @return_rando(ptr %in)
+; CHECK-NEXT: br label %done
+
+  %call = tail call ptr @return_rando(ptr %in)
+  br label %done
+
+false:
+  br label %done
+
+done:
+  %res = phi ptr [ %in, %true ],  [ null, %false ]
+  ret ptr %res
+}
+
+declare ptr @return_input(ptr returned)
+declare ptr @return_rando(ptr)