[X86] Remove useless custom inserter for 64-bit TAILJMP and TCRETURN opcodes

[craig.topper]

Summary

This custom inserter was added in r124272 at which time it added about bunch of Defs for Win64. In r150708, those defs were removed leaving only the "return BB". So I think this means the custom inserter is a NOP these days.

This patch removes the remaining code and stops tagging the instructions for custom insertion

[RKSimon]

LGTM - it doesn't seem to affect the tailcall tests, which are all still present AFAICT

llvm/trunk/lib/Target/X86/X86ISelLowering.cpp

 X86TargetLowering::EmitInstrWithCustomInserter(MachineInstr &MI,
                                                MachineBasicBlock *BB) const {
   MachineFunction *MF = BB->getParent();
   const TargetInstrInfo *TII = Subtarget.getInstrInfo();
   DebugLoc DL = MI.getDebugLoc();
 
   switch (MI.getOpcode()) {
   default: llvm_unreachable("Unexpected instr type to insert");
-  case X86::TAILJMPd64:
-  case X86::TAILJMPr64:
-  case X86::TAILJMPm64:
-  case X86::TAILJMPr64_REX:
-  case X86::TAILJMPm64_REX:
-    llvm_unreachable("TAILJMP64 would not be touched here.");
-  case X86::TCRETURNdi64:
-  case X86::TCRETURNri64:
-  case X86::TCRETURNmi64:
-    return BB;
   case X86::TLS_addr32:
   case X86::TLS_addr64:
   case X86::TLS_base_addr32:
   case X86::TLS_base_addr64:
     return EmitLoweredTLSAddr(MI, BB);
   case X86::CATCHRET:
     return EmitLoweredCatchRet(MI, BB);
   case X86::CATCHPAD:

llvm/trunk/lib/Target/X86/X86InstrControl.td

def CALL64m       : I<0xFF, MRM2m, (outs), (ins i64mem:$dst),
                         IIC_CALL_MEM>,
                       Requires<[In64BitMode,FavorMemIndirectCall]>;
 
   def FARCALL64   : RI<0xFF, MRM3m, (outs), (ins opaque80mem:$dst),
                        "lcall{q}\t{*}$dst", [], IIC_CALL_FAR_MEM>;
 }
 
 let isCall = 1, isTerminator = 1, isReturn = 1, isBarrier = 1,
-    isCodeGenOnly = 1, Uses = [RSP, SSP], usesCustomInserter = 1,
-    SchedRW = [WriteJump] in {
+    isCodeGenOnly = 1, Uses = [RSP, SSP], SchedRW = [WriteJump] in {
   def TCRETURNdi64   : PseudoI<(outs),
                         (ins i64i32imm_pcrel:$dst, i32imm:$offset),
                         []>;
   def TCRETURNri64   : PseudoI<(outs),
                         (ins ptr_rc_tailcall:$dst, i32imm:$offset), []>, NotMemoryFoldable;
   let mayLoad = 1 in
   def TCRETURNmi64   : PseudoI<(outs),
                         (ins i64mem_TC:$dst, i32imm:$offset), []>, NotMemoryFoldable;