This commit introduces two fake instructions MORESTACK_RET and
MORESTACK_RET_RESTORE_R10; which are lowered to a RET and a RET
followed by a MOV respectively.  Having a fake instruction prevents
the verifier from seeing a MachineBasicBlock end with a
non-terminator (MOV).  It also prevents the rather eccentric case of a
MachineBasicBlock ending with RET but having successors nevertheless.

Patch by Sanjoy Das.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143062 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86MCInstLower.cpp b/lib/Target/X86/X86MCInstLower.cpp
index 50bc14d..328cf67 100644
--- a/lib/Target/X86/X86MCInstLower.cpp
+++ b/lib/Target/X86/X86MCInstLower.cpp
@@ -527,6 +527,22 @@
   case X86::XOR16ri:    SimplifyShortImmForm(OutMI, X86::XOR16i16);  break;
   case X86::XOR32ri:    SimplifyShortImmForm(OutMI, X86::XOR32i32);  break;
   case X86::XOR64ri32:  SimplifyShortImmForm(OutMI, X86::XOR64i32);  break;
+
+  case X86::MORESTACK_RET:
+    OutMI.setOpcode(X86::RET);
+    break;
+
+  case X86::MORESTACK_RET_RESTORE_R10: {
+    MCInst retInst;
+
+    OutMI.setOpcode(X86::MOV64rr);
+    OutMI.addOperand(MCOperand::CreateReg(X86::R10));
+    OutMI.addOperand(MCOperand::CreateReg(X86::RAX));
+
+    retInst.setOpcode(X86::RET);
+    AsmPrinter.OutStreamer.EmitInstruction(retInst);
+    break;
+  }
   }
 }