[X86] Remove encoding information from the TAILJMP instructions that are lowered by MCInstLowering. Fix LowerPATCHABLE_TAIL_CALL to also convert them to regular JMP/JCC instructions

[craig.topper]

Summary

There are 5 instructions here that are converted from TAILJMP opcodes to regular JMP/JCC opcodes during MCInstLowering. So normally there encoding information isn't used. The exception being when XRay wraps them in PATCHABLE_TAIL_CALL.

For the ones that weren't already handled in MCInstLowering, add handling for those and remove their encoding information.

This patch fixes PATCHABLE_TAIL_CALL to do the same opcode conversion as the regular lowering patch. Then removes the encoding information.

[craig.topper]

Handle the memory forms in MCInstLower and remove their encoding information. Change how TAILJMPr64 and TAILJMPr64_REX are handled in MCInstLower so that we change their opcodes too.

[craig.topper]

Rebase

[dberris]

I don't see the XRay specific changes... is there something I specifically need to look at here? Looks like the patchable tail call stuff is untouched.

[craig.topper]

llvm/lib/Target/X86/X86MCInstLower.cpp

1385

This line is the part in xray code, @dberris

[dberris]

LGTM from the XRay parts.

llvm/lib/Target/X86/X86MCInstLower.cpp

1385

Ah, right. Thanks!

llvm/lib/Target/X86/X86InstrControl.td

let isCall = 1, isTerminator = 1, isReturn = 1, isBarrier = 1,
   def TCRETURNdi : PseudoI<(outs),
                      (ins i32imm_pcrel:$dst, i32imm:$offset), []>, NotMemoryFoldable;
   def TCRETURNri : PseudoI<(outs),
                      (ins ptr_rc_tailcall:$dst, i32imm:$offset), []>, NotMemoryFoldable;
   let mayLoad = 1 in
   def TCRETURNmi : PseudoI<(outs),
                      (ins i32mem_TC:$dst, i32imm:$offset), []>;
 
+  def TAILJMPd : PseudoI<(outs), (ins i32imm_pcrel:$dst), []>;
+
+  def TAILJMPr : PseudoI<(outs), (ins ptr_rc_tailcall:$dst), []>;
   // FIXME: The should be pseudo instructions that are lowered when going to
   // mcinst.
-  def TAILJMPd : Ii32PCRel<0xE9, RawFrm, (outs),
-                           (ins i32imm_pcrel:$dst), "jmp\t$dst", []>;
-
-  def TAILJMPr : I<0xFF, MRM4r, (outs), (ins ptr_rc_tailcall:$dst),
-                   "", []>;  // FIXME: Remove encoding when JIT is dead.
   let mayLoad = 1 in
   def TAILJMPm : I<0xFF, MRM4m, (outs), (ins i32mem_TC:$dst),
                    "jmp{l}\t{*}$dst", []>;
 }
 
 // Conditional tail calls are similar to the above, but they are branches
 // rather than barriers, and they use EFLAGS.
 let isCall = 1, isTerminator = 1, isReturn = 1, isBranch = 1,
     isCodeGenOnly = 1, SchedRW = [WriteJumpLd] in
   let Uses = [ESP, EFLAGS, SSP] in {
   def TCRETURNdicc : PseudoI<(outs),
                      (ins i32imm_pcrel:$dst, i32imm:$offset, i32imm:$cond), []>;
 
   // This gets substituted to a conditional jump instruction in MC lowering.
-  def TAILJMPd_CC : Ii32PCRel<0x80, RawFrm, (outs),
-                           (ins i32imm_pcrel:$dst, i32imm:$cond), "", []>;
+  def TAILJMPd_CC : PseudoI<(outs), (ins i32imm_pcrel:$dst, i32imm:$cond), []>;
 }
 
 
 //===----------------------------------------------------------------------===//
 //  Call Instructions...
 //
 
 // RSP is marked as a use to prevent stack-pointer assignments that appear
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;
 
-  def TAILJMPd64 : Ii32PCRel<0xE9, RawFrm, (outs), (ins i64i32imm_pcrel:$dst),
-                   "jmp\t$dst", []>;
+  def TAILJMPd64 : PseudoI<(outs), (ins i64i32imm_pcrel:$dst), []>;
 
   def TAILJMPr64 : I<0xFF, MRM4r, (outs), (ins ptr_rc_tailcall:$dst),
                      "jmp{q}\t{*}$dst", []>;
 
   let mayLoad = 1 in
   def TAILJMPm64 : I<0xFF, MRM4m, (outs), (ins i64mem_TC:$dst),
                      "jmp{q}\t{*}$dst", []>;
 

 let isCall = 1, isTerminator = 1, isReturn = 1, isBranch = 1,
     isCodeGenOnly = 1, SchedRW = [WriteJumpLd] in
   let Uses = [RSP, EFLAGS, SSP] in {
   def TCRETURNdi64cc : PseudoI<(outs),
                            (ins i64i32imm_pcrel:$dst, i32imm:$offset,
                             i32imm:$cond), []>;
 
   // This gets substituted to a conditional jump instruction in MC lowering.
-  def TAILJMPd64_CC : Ii32PCRel<0x80, RawFrm, (outs),
-                           (ins i64i32imm_pcrel:$dst, i32imm:$cond), "", []>;
+  def TAILJMPd64_CC : PseudoI<(outs),
+                              (ins i64i32imm_pcrel:$dst, i32imm:$cond), []>;
 }

llvm/lib/Target/X86/X86MCInstLower.cpp

case MachineOperand::MO_BlockAddress:
     return LowerSymbolOperand(
         MO, AsmPrinter.GetBlockAddressSymbol(MO.getBlockAddress()));
   case MachineOperand::MO_RegisterMask:
     // Ignore call clobbers.
     return None;
   }
 }
 
+// Replace TAILJMP opcodes with their equivalent opcodes that have encoding
+// information.
+static unsigned convertTailJumpOpcode(unsigned Opcode) {
+  switch (Opcode) {
+  case X86::TAILJMPr:
+    Opcode = X86::JMP32r;
+    break;
+  case X86::TAILJMPd:
+  case X86::TAILJMPd64:
+    Opcode = X86::JMP_1;
+    break;
+  case X86::TAILJMPd_CC:
+  case X86::TAILJMPd64_CC:
+    Opcode = X86::JCC_1;
+    break;
+  }
+
+  return Opcode;
+}
+
 void X86MCInstLower::Lower(const MachineInstr *MI, MCInst &OutMI) const {
   OutMI.setOpcode(MI->getOpcode());
 
   for (const MachineOperand &MO : MI->operands())
     if (auto MaybeMCOp = LowerMachineOperand(MI, MO))
       OutMI.addOperand(MaybeMCOp.getValue());
 
   // Handle a few special cases to eliminate operand modifiers.
case X86::CATCHRET: {
     const X86Subtarget &Subtarget = AsmPrinter.getSubtarget();
     unsigned ReturnReg = Subtarget.is64Bit() ? X86::RAX : X86::EAX;
     OutMI = MCInst();
     OutMI.setOpcode(getRetOpcode(Subtarget));
     OutMI.addOperand(MCOperand::createReg(ReturnReg));
     break;
   }
 
-    // TAILJMPd, TAILJMPd64, TailJMPd_cc - Lower to the correct jump
-    // instruction.
-    {
-      unsigned Opcode;
-    case X86::TAILJMPr:
-      Opcode = X86::JMP32r;
-      goto SetTailJmpOpcode;
-    case X86::TAILJMPd:
-    case X86::TAILJMPd64:
-      Opcode = X86::JMP_1;
-      goto SetTailJmpOpcode;
-
-    SetTailJmpOpcode:
-      MCOperand Saved = OutMI.getOperand(0);
-      OutMI = MCInst();
-      OutMI.setOpcode(Opcode);
-      OutMI.addOperand(Saved);
-      break;
-    }
-
+  case X86::TAILJMPd64: {
+    unsigned Opcode = convertTailJumpOpcode(OutMI.getOpcode());
   case X86::TAILJMPd_CC:
   case X86::TAILJMPd64_CC: {
+    unsigned Opcode = convertTailJumpOpcode(OutMI.getOpcode());
     MCOperand Saved = OutMI.getOperand(0);
     MCOperand Saved2 = OutMI.getOperand(1);
     OutMI = MCInst();
-    OutMI.setOpcode(X86::JCC_1);
+    OutMI.setOpcode(Opcode);
     OutMI.addOperand(Saved);
     OutMI.addOperand(Saved2);
     break;
   }
 
   case X86::DEC16r:
   case X86::DEC32r:
   case X86::INC16r:
void X86AsmPrinter::LowerPATCHABLE_TAIL_CALL(const MachineInstr &MI,
   // an operand (computed as an offset from the jmp instruction).
   // FIXME: Find another less hacky way do force the relative jump.
   OutStreamer->EmitBytes("\xeb\x09");
   EmitNops(*OutStreamer, 9, Subtarget->is64Bit(), getSubtargetInfo());
   OutStreamer->EmitLabel(Target);
   recordSled(CurSled, MI, SledKind::TAIL_CALL);
 
   unsigned OpCode = MI.getOperand(0).getImm();
+  OpCode = convertTailJumpOpcode(OpCode);
   MCInst TC;
   TC.setOpcode(OpCode);
 
   // Before emitting the instruction, add a comment to indicate that this is
   // indeed a tail call.
   OutStreamer->AddComment("TAILCALL");
   for (auto &MO : make_range(MI.operands_begin() + 1, MI.operands_end()))
     if (auto MaybeOperand = MCIL.LowerMachineOperand(&MI, MO))