Revert "[X86] Clear kill flags when rewriting SETCC uses in flag copy lowering."

This reverts commit 7550f14.

I botched the bug number.

Author: topperc

llvm/lib/Target/X86/X86FlagsCopyLowering.cpp

@@ -964,11 +964,7 @@ void X86FlagsCopyLoweringPass::rewriteSetCC(MachineBasicBlock &TestMBB,
   if (!SetCCI.mayStore()) {
     assert(SetCCI.getOperand(0).isReg() &&
            "Cannot have a non-register defined operand to SETcc!");
-    Register OldReg = SetCCI.getOperand(0).getReg();
-    // Drop Kill flags on the old register before replacing. CondReg may have
-    // a longer live range.
-    MRI->clearKillFlags(OldReg);
-    MRI->replaceRegWith(OldReg, CondReg);
+    MRI->replaceRegWith(SetCCI.getOperand(0).getReg(), CondReg);
     SetCCI.eraseFromParent();
     return;
   }

llvm/test/CodeGen/X86/flags-copy-lowering.mir

@@ -250,10 +250,10 @@ body:             |
     MOV8mr $rsp, 1, $noreg, -16, $noreg, killed %5
   ; CHECK-NOT:     $eflags =
   ; CHECK-NOT:             = SET{{.*}}
-  ; CHECK:         MOV8mr {{.*}}, %[[A_REG]]
-  ; CHECK-NEXT:    MOV8mr {{.*}}, %[[B_REG]]
-  ; CHECK-NEXT:    MOV8mr {{.*}}, %[[E_REG]]
-  ; CHECK-NOT:     MOV8mr {{.*}}, %[[NE_REG]]
+  ; CHECK:         MOV8mr {{.*}}, killed %[[A_REG]]
+  ; CHECK-NEXT:    MOV8mr {{.*}}, killed %[[B_REG]]
+  ; CHECK-NEXT:    MOV8mr {{.*}}, killed %[[E_REG]]
+  ; CHECK-NOT:     MOV8mr {{.*}}, killed %[[NE_REG]]
 
     RET 0