Win64: Don't use REX prefix for direct tail calls

The REX prefix should be used on indirect jmps, but not direct ones.
For direct jumps, the unwinder looks at the offset to determine if
it's inside the current function.

Differential Revision: https://reviews.llvm.org/D24359

llvm-svn: 281003

5 files changed, 4 insertions, 8 deletions

diff --git a/llvm/lib/Target/X86/X86ExpandPseudo.cpp b/llvm/lib/Target/X86/X86ExpandPseudo.cpp
index 4bd01b8f00f..701b3f29957 100644
--- a/llvm/lib/Target/X86/X86ExpandPseudo.cpp
+++ b/llvm/lib/Target/X86/X86ExpandPseudo.cpp
@@ -121,7 +121,9 @@ bool X86ExpandPseudo::ExpandMI(MachineBasicBlock &MBB,
         Op = X86::TAILJMPd_CC;
         break;
       default:
-        Op = IsWin64 ? X86::TAILJMPd64_REX : X86::TAILJMPd64;
+        // Note: Win64 uses REX prefixes indirect jumps out of functions, but
+        // not direct ones.
+        Op = X86::TAILJMPd64;
         break;
       }
       MachineInstrBuilder MIB = BuildMI(MBB, MBBI, DL, TII->get(Op));
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 30dbe42bec2..62366850a6f 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -24521,7 +24521,6 @@ X86TargetLowering::EmitInstrWithCustomInserter(MachineInstr &MI,
   case X86::TAILJMPd64:
   case X86::TAILJMPr64:
   case X86::TAILJMPm64:
-  case X86::TAILJMPd64_REX:
   case X86::TAILJMPr64_REX:
   case X86::TAILJMPm64_REX:
     llvm_unreachable("TAILJMP64 would not be touched here.");
diff --git a/llvm/lib/Target/X86/X86InstrControl.td b/llvm/lib/Target/X86/X86InstrControl.td
index 87f81ee73ac..77796d23736 100644
--- a/llvm/lib/Target/X86/X86InstrControl.td
+++ b/llvm/lib/Target/X86/X86InstrControl.td
@@ -323,11 +323,8 @@ let isCall = 1, isTerminator = 1, isReturn = 1, isBarrier = 1,
   def TAILJMPm64 : I<0xFF, MRM4m, (outs), (ins i64mem_TC:$dst),
                      "jmp{q}\t{*}$dst", [], IIC_JMP_MEM>;
 
-  // Win64 wants jumps leaving the function to have a REX_W prefix.
+  // Win64 wants indirect jumps leaving the function to have a REX_W prefix.
   let hasREX_WPrefix = 1 in {
-    def TAILJMPd64_REX : Ii32PCRel<0xE9, RawFrm, (outs),
-                                   (ins i64i32imm_pcrel:$dst),
-                                   "rex64 jmp\t$dst", [], IIC_JMP_REL>;
     def TAILJMPr64_REX : I<0xFF, MRM4r, (outs), (ins ptr_rc_tailcall:$dst),
                            "rex64 jmp{q}\t{*}$dst", [], IIC_JMP_MEM>;
 
diff --git a/llvm/lib/Target/X86/X86InstrInfo.cpp b/llvm/lib/Target/X86/X86InstrInfo.cpp
index d9a0897c24d..fda3f85a198 100644
--- a/llvm/lib/Target/X86/X86InstrInfo.cpp
+++ b/llvm/lib/Target/X86/X86InstrInfo.cpp
@@ -8286,7 +8286,6 @@ bool X86InstrInfo::isTailCall(const MachineInstr &Inst) const {
     case X86::TAILJMPd64:
     case X86::TAILJMPm64:
     case X86::TAILJMPr64:
-    case X86::TAILJMPd64_REX:
     case X86::TAILJMPm64_REX:
     case X86::TAILJMPr64_REX:
       return true;
diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
index 46197756566..9ce647a8068 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -1311,7 +1311,6 @@ void X86AsmPrinter::EmitInstruction(const MachineInstr *MI) {
   case X86::TAILJMPd64:
   case X86::TAILJMPr64_REX:
   case X86::TAILJMPm64_REX:
-  case X86::TAILJMPd64_REX:
     // Lower these as normal, but add some comments.
     OutStreamer->AddComment("TAILCALL");
     break;