DAG: Remove TargetLowering::checkForPhysRegDependency (#161787)

I have no idea why this was here. The only implementation was AMDGPU,
which was essentially repeating the generic logic but for one specific
case.

Author: arsenm

llvm/include/llvm/CodeGen/TargetLowering.h

@@ -4654,23 +4654,6 @@ class LLVM_ABI TargetLowering : public TargetLoweringBase {
     return false;
   }
 
-  /// Allows the target to handle physreg-carried dependency
-  /// in target-specific way. Used from the ScheduleDAGSDNodes to decide whether
-  /// to add the edge to the dependency graph.
-  /// Def - input: Selection DAG node defininfg physical register
-  /// User - input: Selection DAG node using physical register
-  /// Op - input: Number of User operand
-  /// PhysReg - inout: set to the physical register if the edge is
-  /// necessary, unchanged otherwise
-  /// Cost - inout: physical register copy cost.
-  /// Returns 'true' is the edge is necessary, 'false' otherwise
-  virtual bool checkForPhysRegDependency(SDNode *Def, SDNode *User, unsigned Op,
-                                         const TargetRegisterInfo *TRI,
-                                         const TargetInstrInfo *TII,
-                                         MCRegister &PhysReg, int &Cost) const {
-    return false;
-  }
-
   /// Target-specific combining of register parts into its original value
   virtual SDValue
   joinRegisterPartsIntoValue(SelectionDAG &DAG, const SDLoc &DL,

llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp

@@ -111,15 +111,11 @@ SUnit *ScheduleDAGSDNodes::Clone(SUnit *Old) {
 static void CheckForPhysRegDependency(SDNode *Def, SDNode *User, unsigned Op,
                                       const TargetRegisterInfo *TRI,
                                       const TargetInstrInfo *TII,
-                                      const TargetLowering &TLI,
                                       MCRegister &PhysReg, int &Cost) {
   if (Op != 2 || User->getOpcode() != ISD::CopyToReg)
     return;
 
   Register Reg = cast<RegisterSDNode>(User->getOperand(1))->getReg();
-  if (TLI.checkForPhysRegDependency(Def, User, Op, TRI, TII, PhysReg, Cost))
-    return;
-
   if (Reg.isVirtual())
     return;
 
@@ -490,8 +486,7 @@ void ScheduleDAGSDNodes::AddSchedEdges() {
         MCRegister PhysReg;
         int Cost = 1;
         // Determine if this is a physical register dependency.
-        const TargetLowering &TLI = DAG->getTargetLoweringInfo();
-        CheckForPhysRegDependency(OpN, N, i, TRI, TII, TLI, PhysReg, Cost);
+        CheckForPhysRegDependency(OpN, N, i, TRI, TII, PhysReg, Cost);
         assert((!PhysReg || !isChain) && "Chain dependence via physreg data?");
         // FIXME: See ScheduleDAGSDNodes::EmitCopyFromReg. For now, scheduler
         // emits a copy from the physical register to a virtual register unless

llvm/lib/Target/AMDGPU/SIISelLowering.cpp

@@ -18860,31 +18860,6 @@ SITargetLowering::getTargetMMOFlags(const Instruction &I) const {
   return Flags;
 }
 
-bool SITargetLowering::checkForPhysRegDependency(
-    SDNode *Def, SDNode *User, unsigned Op, const TargetRegisterInfo *TRI,
-    const TargetInstrInfo *TII, MCRegister &PhysReg, int &Cost) const {
-  if (User->getOpcode() != ISD::CopyToReg)
-    return false;
-  if (!Def->isMachineOpcode())
-    return false;
-  MachineSDNode *MDef = dyn_cast<MachineSDNode>(Def);
-  if (!MDef)
-    return false;
-
-  unsigned ResNo = User->getOperand(Op).getResNo();
-  if (User->getOperand(Op)->getValueType(ResNo) != MVT::i1)
-    return false;
-  const MCInstrDesc &II = TII->get(MDef->getMachineOpcode());
-  if (II.isCompare() && II.hasImplicitDefOfPhysReg(AMDGPU::SCC)) {
-    PhysReg = AMDGPU::SCC;
-    const TargetRegisterClass *RC =
-        TRI->getMinimalPhysRegClass(PhysReg, Def->getSimpleValueType(ResNo));
-    Cost = RC->expensiveOrImpossibleToCopy() ? -1 : RC->getCopyCost();
-    return true;
-  }
-  return false;
-}
-
 void SITargetLowering::emitExpandAtomicAddrSpacePredicate(
     Instruction *AI) const {
   // Given: atomicrmw fadd ptr %addr, float %val ordering

llvm/lib/Target/AMDGPU/SIISelLowering.h

@@ -561,11 +561,6 @@ class SITargetLowering final : public AMDGPUTargetLowering {
   bool denormalsEnabledForType(const SelectionDAG &DAG, EVT VT) const;
   bool denormalsEnabledForType(LLT Ty, const MachineFunction &MF) const;
 
-  bool checkForPhysRegDependency(SDNode *Def, SDNode *User, unsigned Op,
-                                 const TargetRegisterInfo *TRI,
-                                 const TargetInstrInfo *TII,
-                                 MCRegister &PhysReg, int &Cost) const override;
-
   bool isKnownNeverNaNForTargetNode(SDValue Op, const APInt &DemandedElts,
                                     const SelectionDAG &DAG, bool SNaN = false,
                                     unsigned Depth = 0) const override;