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

9 files changed, 8 insertions, 12 deletions

diff --git a/llvm/lib/Target/X86/X86ExpandPseudo.cpp b/llvm/lib/Target/X86/X86ExpandPseudo.cpp
index 4bd01b8..701b3f2 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 30dbe42..6236685 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 87f81ee..77796d2 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 d9a0897..fda3f85 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 4619775..9ce647a 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;
diff --git a/llvm/test/CodeGen/X86/seh-catchpad.ll b/llvm/test/CodeGen/X86/seh-catchpad.ll
index d9b4c5c..4b2a9f9b 100644
--- a/llvm/test/CodeGen/X86/seh-catchpad.ll
+++ b/llvm/test/CodeGen/X86/seh-catchpad.ll
@@ -173,7 +173,7 @@ entry:
 ; CHECK: "?filt$0@0@main@@":                     # @"\01?filt$0@0@main@@"
 ; CHECK: .seh_proc "?filt$0@0@main@@"
 ; CHECK:         .seh_endprologue
-; CHECK:         rex64 jmp       filt  # TAILCALL
+; CHECK:         jmp       filt  # TAILCALL
 ; CHECK:         .seh_handlerdata
 
 declare i32 @filt() #1
diff --git a/llvm/test/CodeGen/X86/tail-call-win64.ll b/llvm/test/CodeGen/X86/tail-call-win64.ll
index fb10d5d..6d23020 100644
--- a/llvm/test/CodeGen/X86/tail-call-win64.ll
+++ b/llvm/test/CodeGen/X86/tail-call-win64.ll
@@ -22,7 +22,7 @@ define void @tail_jmp_imm() {
 }
 
 ; CHECK-LABEL: tail_jmp_imm:
-; CHECK: rex64 jmp tail_tgt
+; CHECK: jmp tail_tgt
 
 @g_fptr = global void ()* @tail_tgt
 
diff --git a/llvm/test/CodeGen/X86/win64_sibcall.ll b/llvm/test/CodeGen/X86/win64_sibcall.ll
index 4001f63..4bba0e1 100644
--- a/llvm/test/CodeGen/X86/win64_sibcall.ll
+++ b/llvm/test/CodeGen/X86/win64_sibcall.ll
@@ -21,7 +21,7 @@ entry:
 
 ; WIN_X64:	xorl	%r8d, %r8d
 ; WIN_X64:	popq	%rax
-; WIN_X64:	rex64 jmp	C2              # TAILCALL
+; WIN_X64:	jmp	  C2                  # TAILCALL
 ; LINUX:	xorl	%edx, %edx
 ; LINUX:	jmp	C2                      # TAILCALL
 
diff --git a/llvm/test/DebugInfo/COFF/register-variables.ll b/llvm/test/DebugInfo/COFF/register-variables.ll
index 9bb7828..5392ea6 100644
--- a/llvm/test/DebugInfo/COFF/register-variables.ll
+++ b/llvm/test/DebugInfo/COFF/register-variables.ll
@@ -54,7 +54,7 @@
 ; ASM:         addq    $32, %rsp
 ; ASM:         popq    %rsi
 ; ASM: [[func_end:\.Ltmp.*]]:
-; ASM:         rex64 jmp       putint          # TAILCALL
+; ASM:         jmp     putint                  # TAILCALL
 
 ; ASM:         .short  4414                    # Record kind: S_LOCAL
 ; ASM:         .asciz  "p"