[AMDGPU] si-peephole-sdwa: reuse getOne{NonDBGUse,Def} (NFC) (llvm#156455)

This patch changes the findSingleRegDef function from si-peephole-sdwa
to reuse MachineRegisterInfo::getOneDef and findSingleRefUse to use a
new MachineRegisterInfo::getOneNonDBGUse function.

Author: frederik-h

llvm/include/llvm/CodeGen/MachineRegisterInfo.h

@@ -579,6 +579,10 @@ class MachineRegisterInfo {
   /// multiple uses.
   LLVM_ABI bool hasOneNonDBGUser(Register RegNo) const;
 
+  /// If the register has a single non-Debug use, returns it; otherwise returns
+  /// nullptr.
+  LLVM_ABI MachineOperand *getOneNonDBGUse(Register RegNo) const;
+
   /// If the register has a single non-Debug instruction using the specified
   /// register, returns it; otherwise returns nullptr.
   LLVM_ABI MachineInstr *getOneNonDBGUser(Register RegNo) const;

llvm/lib/CodeGen/MachineRegisterInfo.cpp

@@ -432,6 +432,11 @@ bool MachineRegisterInfo::hasOneNonDBGUser(Register RegNo) const {
   return hasSingleElement(use_nodbg_instructions(RegNo));
 }
 
+MachineOperand *MachineRegisterInfo::getOneNonDBGUse(Register RegNo) const {
+  auto RegNoDbgUses = use_nodbg_operands(RegNo);
+  return hasSingleElement(RegNoDbgUses) ? &*RegNoDbgUses.begin() : nullptr;
+}
+
 MachineInstr *MachineRegisterInfo::getOneNonDBGUser(Register RegNo) const {
   auto RegNoDbgUsers = use_nodbg_instructions(RegNo);
   return hasSingleElement(RegNoDbgUsers) ? &*RegNoDbgUsers.begin() : nullptr;

llvm/lib/Target/AMDGPU/SIPeepholeSDWA.cpp

@@ -291,39 +291,15 @@ static MachineOperand *findSingleRegUse(const MachineOperand *Reg,
   if (!Reg->isReg() || !Reg->isDef())
     return nullptr;
 
-  MachineOperand *ResMO = nullptr;
-  for (MachineOperand &UseMO : MRI->use_nodbg_operands(Reg->getReg())) {
-    // If there exist use of subreg of Reg then return nullptr
-    if (!isSameReg(UseMO, *Reg))
-      return nullptr;
-
-    // Check that there is only one instruction that uses Reg
-    if (!ResMO) {
-      ResMO = &UseMO;
-    } else if (ResMO->getParent() != UseMO.getParent()) {
-      return nullptr;
-    }
-  }
-
-  return ResMO;
+  return MRI->getOneNonDBGUse(Reg->getReg());
 }
 
 static MachineOperand *findSingleRegDef(const MachineOperand *Reg,
                                         const MachineRegisterInfo *MRI) {
   if (!Reg->isReg())
     return nullptr;
 
-  MachineInstr *DefInstr = MRI->getUniqueVRegDef(Reg->getReg());
-  if (!DefInstr)
-    return nullptr;
-
-  for (auto &DefMO : DefInstr->defs()) {
-    if (DefMO.isReg() && DefMO.getReg() == Reg->getReg())
-      return &DefMO;
-  }
-
-  // Ignore implicit defs.
-  return nullptr;
+  return MRI->getOneDef(Reg->getReg());
 }
 
 /// Combine an SDWA instruction's existing SDWA selection \p Sel with