[BOLT][NFC] Simplify MCPlusBuilder::getRegSize

[Amir]

Incorporated into D145828

bolt/lib/Core/MCPlusBuilder.cpp

LLVM_DEBUG({
     }
   });
 }
 
 uint8_t MCPlusBuilder::getRegSize(MCPhysReg Reg) const {
   // SizeMap caches a mapping of registers to their sizes
   static std::vector<uint8_t> SizeMap;
 
-  if (SizeMap.size() > 0) {
+  if (SizeMap.size() > 0)
     return SizeMap[Reg];
-  }
+
   SizeMap = std::vector<uint8_t>(RegInfo->getNumRegs());
   // Build size map
-  for (auto I = RegInfo->regclass_begin(), E = RegInfo->regclass_end(); I != E;
-       ++I) {
-    for (MCPhysReg Reg : *I)
-      SizeMap[Reg] = I->getSizeInBits() / 8;
-  }
+  for (const MCRegisterClass &RC : RegInfo->regclasses())
+    for_each(RC, [&](MCPhysReg Reg) { SizeMap[Reg] = RC.getSizeInBits() / 8; });
 
   return SizeMap[Reg];
 }
 
 bool MCPlusBuilder::setOperandToSymbolRef(MCInst &Inst, int OpNum,
                                           const MCSymbol *Symbol,
                                           int64_t Addend, MCContext *Ctx,
                                           uint64_t RelType) const {