[SelectDagISEL] refactor HandlePHINodesInSuccessorBlocks NFC.

[nickdesaulniers]

Summary

While working on this code to support outputs from callbr along indirect
branches, I kept making these changes again and again. Precommit these.

[arsenm]

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

10876–10878

Can drop the &

[nickdesaulniers]

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

10876–10878

Aren't EVTs larger than the word size? Isn't it cheaper to take by ref to avoid a copy?

[craig.topper]

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

10876–10878

It's an int and a pointer. It's going to get copied to pass by value to getNumRegisters anyway.

[nickdesaulniers]

• drop reference

[craig.topper]

LGTM

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

 /// ensure constants are generated when needed.  Remember the virtual registers
 /// that need to be added to the Machine PHI nodes as input.  We cannot just
 /// directly add them, because expansion might result in multiple MBB's for one
 /// BB.  As such, the start of the BB might correspond to a different MBB than
 /// the end.
 void
 SelectionDAGBuilder::HandlePHINodesInSuccessorBlocks(const BasicBlock *LLVMBB) {
   const TargetLowering &TLI = DAG.getTargetLoweringInfo();
-  const Instruction *TI = LLVMBB->getTerminator();
 
   SmallPtrSet<MachineBasicBlock *, 4> SuccsHandled;
 
   // Check PHI nodes in successors that expect a value to be available from this
   // block.
-  for (unsigned succ = 0, e = TI->getNumSuccessors(); succ != e; ++succ) {
-    const BasicBlock *SuccBB = TI->getSuccessor(succ);
+  for (const BasicBlock *SuccBB : successors(LLVMBB->getTerminator())) {
     if (!isa<PHINode>(SuccBB->begin())) continue;
     MachineBasicBlock *SuccMBB = FuncInfo.MBBMap[SuccBB];
 
     // If this terminator has multiple identical successors (common for
     // switches), only handle each succ once.
     if (!SuccsHandled.insert(SuccMBB).second)
       continue;
 
for (const PHINode &PN : SuccBB->phis()) {
 
       // Skip empty types
       if (PN.getType()->isEmptyTy())
         continue;
 
       unsigned Reg;
       const Value *PHIOp = PN.getIncomingValueForBlock(LLVMBB);
 
-      if (const Constant *C = dyn_cast<Constant>(PHIOp)) {
+      if (const auto *C = dyn_cast<Constant>(PHIOp)) {
         unsigned &RegOut = ConstantsOut[C];
         if (RegOut == 0) {
           RegOut = FuncInfo.CreateRegs(C);
           // We need to zero/sign extend ConstantInt phi operands to match
           // assumptions in FunctionLoweringInfo::ComputePHILiveOutRegInfo.
           ISD::NodeType ExtendType = ISD::ANY_EXTEND;
           if (auto *CI = dyn_cast<ConstantInt>(C))
             ExtendType = TLI.signExtendConstant(CI) ? ISD::SIGN_EXTEND
for (const PHINode &PN : SuccBB->phis()) {
           CopyValueToVirtualRegister(PHIOp, Reg);
         }
       }
 
       // Remember that this register needs to added to the machine PHI node as
       // the input for this MBB.
       SmallVector<EVT, 4> ValueVTs;
       ComputeValueVTs(TLI, DAG.getDataLayout(), PN.getType(), ValueVTs);
-      for (unsigned vti = 0, vte = ValueVTs.size(); vti != vte; ++vti) {
-        EVT VT = ValueVTs[vti];
-        unsigned NumRegisters = TLI.getNumRegisters(*DAG.getContext(), VT);
-        for (unsigned i = 0, e = NumRegisters; i != e; ++i)
+      for (EVT VT : ValueVTs) {
+        const unsigned NumRegisters = TLI.getNumRegisters(*DAG.getContext(), VT);
+        for (unsigned i = 0; i != NumRegisters; ++i)
           FuncInfo.PHINodesToUpdate.push_back(
               std::make_pair(&*MBBI++, Reg + i));
         Reg += NumRegisters;
       }
     }
   }
 
   ConstantsOut.clear();