Revert rL357745: [SelectionDAG] Compute known bits of CopyFromReg

Certain optimisations from ConstantHoisting and CGP rely on Selection DAG not
seeing through to the constant in other blocks. Revert this patch while we come
up with a better way to handle that.

I will try to follow this up with some better tests.

llvm-svn: 358113

1 files changed, 0 insertions, 20 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index caa3f14b8a1..c017d6d6eae 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -31,7 +31,6 @@
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineMemOperand.h"
-#include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/RuntimeLibcalls.h"
 #include "llvm/CodeGen/SelectionDAGAddressAnalysis.h"
 #include "llvm/CodeGen/SelectionDAGNodes.h"
@@ -3208,25 +3207,6 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
     Known.One &= Known2.One;
     break;
   }
-  case ISD::CopyFromReg: {
-    auto R = cast<RegisterSDNode>(Op.getOperand(1));
-    const unsigned Reg = R->getReg();
-
-    const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
-    if (!TRI->isVirtualRegister(Reg))
-      break;
-
-    const MachineRegisterInfo *MRI = &MF->getRegInfo();
-    if (!MRI->hasOneDef(Reg))
-      break;
-
-    const FunctionLoweringInfo::LiveOutInfo *LOI = FLI->GetLiveOutRegInfo(Reg);
-    if (!LOI || LOI->Known.getBitWidth() != BitWidth)
-      break;
-
-    Known = LOI->Known;
-    break;
-  }
   case ISD::FrameIndex:
   case ISD::TargetFrameIndex:
     TLI->computeKnownBitsForFrameIndex(Op, Known, DemandedElts, *this, Depth);