[llvm] Use hasSingleElement (NFC)

include/llvm/CodeGen/MachineRegisterInfo.h

@@ -442,10 +442,7 @@ public:
   /// Return true if there is exactly one operand defining the specified
   /// register.
   bool hasOneDef(Register RegNo) const {
-    def_iterator DI = def_begin(RegNo);
-    if (DI == def_end())
-      return false;
-    return ++DI == def_end();
+    return hasSingleElement(def_operands(RegNo));
   }
 
   /// Returns the defining operand if there is exactly one operand defining the
@@ -511,10 +508,7 @@ public:
   /// hasOneUse - Return true if there is exactly one instruction using the
   /// specified register.
   bool hasOneUse(Register RegNo) const {
-    use_iterator UI = use_begin(RegNo);
-    if (UI == use_end())
-      return false;
-    return ++UI == use_end();
+    return hasSingleElement(use_operands(RegNo));
   }
 
   /// use_nodbg_iterator/use_nodbg_begin/use_nodbg_end - Walk all uses of the

include/llvm/CodeGen/SelectionDAGNodes.h

@@ -689,9 +689,7 @@ public:
   bool use_empty() const { return UseList == nullptr; }
 
   /// Return true if there is exactly one use of this node.
-  bool hasOneUse() const {
-    return !use_empty() && std::next(use_begin()) == use_end();
-  }
+  bool hasOneUse() const { return hasSingleElement(uses()); }
 
   /// Return the number of uses of this node. This method takes
   /// time proportional to the number of uses.

include/llvm/IR/Value.h

@@ -434,11 +434,7 @@ public:
   ///
   /// This is specialized because it is a common request and does not require
   /// traversing the whole use list.
-  bool hasOneUse() const {
-    const_use_iterator I = use_begin(), E = use_end();
-    if (I == E) return false;
-    return ++I == E;
-  }
+  bool hasOneUse() const { return hasSingleElement(uses()); }
 
   /// Return true if this Value has exactly N uses.
   bool hasNUses(unsigned N) const;

lib/CodeGen/MachineRegisterInfo.cpp

@@ -417,17 +417,11 @@ MachineInstr *MachineRegisterInfo::getUniqueVRegDef(Register Reg) const {
 }
 
 bool MachineRegisterInfo::hasOneNonDBGUse(Register RegNo) const {
-  use_nodbg_iterator UI = use_nodbg_begin(RegNo);
-  if (UI == use_nodbg_end())
-    return false;
-  return ++UI == use_nodbg_end();
+  return hasSingleElement(use_nodbg_operands(RegNo));
 }
 
 bool MachineRegisterInfo::hasOneNonDBGUser(Register RegNo) const {
-  use_instr_nodbg_iterator UI = use_instr_nodbg_begin(RegNo);
-  if (UI == use_instr_nodbg_end())
-    return false;
-  return ++UI == use_instr_nodbg_end();
+  return hasSingleElement(use_nodbg_instructions(RegNo));
 }
 
 /// clearKillFlags - Iterate over all the uses of the given register and

lib/DebugInfo/DWARF/DWARFUnit.cpp

@@ -194,13 +194,12 @@ Optional<object::SectionedAddress>
 DWARFUnit::getAddrOffsetSectionItem(uint32_t Index) const {
   if (IsDWO) {
     auto R = Context.info_section_units();
-    auto I = R.begin();
     // Surprising if a DWO file has more than one skeleton unit in it - this
     // probably shouldn't be valid, but if a use case is found, here's where to
     // support it (probably have to linearly search for the matching skeleton CU
     // here)
-    if (I != R.end() && std::next(I) == R.end())
-      return (*I)->getAddrOffsetSectionItem(Index);
+    if (hasSingleElement(R))
+      return (*R.begin())->getAddrOffsetSectionItem(Index);
   }
   if (!AddrOffsetSectionBase)
     return None;