have the mc lowering process handle a few tail call forms, lowering them to

jumps where possible and turning the TAILCALL marker in the instruction
asm string into a proper comment.

This eliminates a FIXME and is on the path to finishing:
rdar://7639610 - eliminate encoding and asm info for TAILJMPd TAILJMPr TAILJMPn, etc.

However, I can't eliminate the encodings for these instructions because the JIT
still exists and has its own copy of the encoder, sigh.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107946 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 19 insertions, 13 deletions

diff --git a/lib/Target/X86/AsmPrinter/X86MCInstLower.cpp b/lib/Target/X86/AsmPrinter/X86MCInstLower.cpp
index 737b360..09f150b 100644
--- a/lib/Target/X86/AsmPrinter/X86MCInstLower.cpp
+++ b/lib/Target/X86/AsmPrinter/X86MCInstLower.cpp
@@ -395,10 +395,9 @@ void X86MCInstLower::Lower(const MachineInstr *MI, MCInst &OutMI) const {
     LowerUnaryToTwoAddr(OutMI, X86::XOR32rr); // MOV32r0 -> XOR32rr
     break;
 
-  // TAILJMPr, TAILJMPr64, CALL64r, CALL64pcrel32 - These instructions have
+  // TAILJMPr64, CALL64r, CALL64pcrel32 - These instructions have
   // register inputs modeled as normal uses instead of implicit uses.  As such,
   // truncate off all but the first operand (the callee).  FIXME: Change isel.
-  case X86::TAILJMPr:
   case X86::TAILJMPr64:
   case X86::CALL64r:
   case X86::CALL64pcrel32: {
@@ -411,11 +410,20 @@ void X86MCInstLower::Lower(const MachineInstr *MI, MCInst &OutMI) const {
   }
 
   // TAILJMPd, TAILJMPd64 - Lower to the correct jump instructions.
+  case X86::TAILJMPr:
   case X86::TAILJMPd:
   case X86::TAILJMPd64: {
+    unsigned Opcode;
+    switch (OutMI.getOpcode()) {
+    default: assert(0 && "Invalid opcode");
+    case X86::TAILJMPr: Opcode = X86::JMP32r; break;
+    case X86::TAILJMPd:
+    case X86::TAILJMPd64: Opcode = X86::JMP_1; break;
+    }
+    
     MCOperand Saved = OutMI.getOperand(0);
     OutMI = MCInst();
-    OutMI.setOpcode(X86::TAILJMP_1);
+    OutMI.setOpcode(Opcode);
     OutMI.addOperand(Saved);
     break;
   }
@@ -549,6 +557,13 @@ void X86AsmPrinter::EmitInstruction(const MachineInstr *MI) {
     }
     return;
 
+  case X86::TAILJMPr:
+  case X86::TAILJMPd:
+  case X86::TAILJMPd64:
+    // Lower these as normal, but add some comments.
+    OutStreamer.AddComment("TAILCALL");
+    break;
+      
   case X86::MOVPC32r: {
     MCInst TmpInst;
     // This is a pseudo op for a two instruction sequence with a label, which
diff --git a/lib/Target/X86/X86AsmBackend.cpp b/lib/Target/X86/X86AsmBackend.cpp
index 8afaac1..2cf65c1 100644
--- a/lib/Target/X86/X86AsmBackend.cpp
+++ b/lib/Target/X86/X86AsmBackend.cpp
@@ -77,7 +77,6 @@ static unsigned getRelaxedOpcode(unsigned Op) {
   case X86::JG_1:  return X86::JG_4;
   case X86::JLE_1: return X86::JLE_4;
   case X86::JL_1:  return X86::JL_4;
-  case X86::TAILJMP_1:
   case X86::JMP_1: return X86::JMP_4;
   case X86::JNE_1: return X86::JNE_4;
   case X86::JNO_1: return X86::JNO_4;
diff --git a/lib/Target/X86/X86InstrInfo.td b/lib/Target/X86/X86InstrInfo.td
index 15e9f36..1fe373e 100644
--- a/lib/Target/X86/X86InstrInfo.td
+++ b/lib/Target/X86/X86InstrInfo.td
@@ -745,18 +745,10 @@ let isCall = 1, isTerminator = 1, isReturn = 1, isBarrier = 1 in
                  "jmp\t$dst  # TAILCALL",
                  []>;
   def TAILJMPr : I<0xFF, MRM4r, (outs), (ins GR32_TC:$dst, variable_ops), 
-                   "jmp{l}\t{*}$dst  # TAILCALL",
-                 []>;     
+                   "", []>;  // FIXME: Remove encoding when JIT is dead.
   let mayLoad = 1 in
   def TAILJMPm : I<0xFF, MRM4m, (outs), (ins i32mem_TC:$dst, variable_ops),
                    "jmp{l}\t{*}$dst  # TAILCALL", []>;
-
-  // FIXME: This is a hack so that MCInst lowering can preserve the TAILCALL
-  // marker on instructions, while still being able to relax.
-  let isCodeGenOnly = 1 in {
-    def TAILJMP_1 : Ii8PCRel<0xEB, RawFrm, (outs), (ins brtarget8:$dst),
-                         "jmp\t$dst  # TAILCALL", []>;
-  }
 }
 
 //===----------------------------------------------------------------------===//