[X86] Disable conditional tail calls (PR31257)

They are currently modelled incorrectly (as calls, which clobber
registers, confusing e.g. Machine Copy Propagation).

Reverting until we figure out the proper solution.

llvm-svn: 294348

1 files changed, 1 insertions, 8 deletions

diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
index 65949531126..0887643ed5a 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -499,16 +499,11 @@ ReSimplify:
     break;
   }
 
-  // TAILJMPd, TAILJMPd64, TailJMPd_cc - Lower to the correct jump instruction.
+  // TAILJMPd, TAILJMPd64 - 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;
-  case X86::TAILJMPd_CC:
-  case X86::TAILJMPd64_CC:
-    Opcode = X86::GetCondBranchFromCond(
-        static_cast<X86::CondCode>(MI->getOperand(1).getImm()));
-    goto SetTailJmpOpcode;
 
   SetTailJmpOpcode:
     MCOperand Saved = OutMI.getOperand(0);
@@ -1299,11 +1294,9 @@ void X86AsmPrinter::EmitInstruction(const MachineInstr *MI) {
   case X86::TAILJMPr:
   case X86::TAILJMPm:
   case X86::TAILJMPd:
-  case X86::TAILJMPd_CC:
   case X86::TAILJMPr64:
   case X86::TAILJMPm64:
   case X86::TAILJMPd64:
-  case X86::TAILJMPd64_CC:
   case X86::TAILJMPr64_REX:
   case X86::TAILJMPm64_REX:
     // Lower these as normal, but add some comments.