CodeGenPrep: rewrite a few loops in C++11 style

[artagnon]

Summary

I wanted to add some code to CodeGenPrep, but I thought I should get
these nits out of the way first.

[qcolombet]

Hi Ramkumar,

Go ahead with those clean-ups.
If you happen to want to do some other clean-ups, just commit, no need to review :).

Thanks,
-Quentin

[artagnon]

Hi Craig,

I don't have commit access; could you do it for me?

Thanks,
Ram

[silvas]

Doesn't iterating over function give BB's? I.e. shouldn't this be for (BasicBlock &BB : F)?

[artagnon]

It depends on what you want to construct from the iteration. You could construct a BasicBlock, like you said; but this is perfectly valid too: you can try it out, and see that tests pass.

[artagnon]

Revert first hunk, and change the cursor to BasicBlock in the second
and third loops. Do one additional inner loop.

[artagnon]

Revert last hunk. Thanks to Duncan.

[dexonsmith]

LGTM (with a nit). Let me know if you need me to commit it for you.

[artagnon]

Fix nit pointed out by Duncan: BasicBlock* -> BasicBlock *.

[dexonsmith]

(Once you have an LGTM, there's no need to repost a review, just
fix it offline and commit.)

Do you need someone to commit this for you?

[artagnon]

Yes, please commit for me if this is okay.

lib/CodeGen/CodeGenPrepare.cpp

while (MadeChange) {
     EverMadeChange |= MadeChange;
   }
 
   SunkAddrs.clear();
 
   if (!DisableBranchOpts) {
     MadeChange = false;
     SmallPtrSet<BasicBlock*, 8> WorkList;
-    for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
-      SmallVector<BasicBlock*, 2> Successors(succ_begin(BB), succ_end(BB));
-      MadeChange |= ConstantFoldTerminator(BB, true);
+    for (BasicBlock &BB : F) {
+      SmallVector<BasicBlock *, 2> Successors(succ_begin(&BB), succ_end(&BB));
+      MadeChange |= ConstantFoldTerminator(&BB, true);
       if (!MadeChange) continue;
 
       for (SmallVectorImpl<BasicBlock*>::iterator
              II = Successors.begin(), IE = Successors.end(); II != IE; ++II)
         if (pred_begin(*II) == pred_end(*II))
           WorkList.insert(*II);
     }
 
bool CodeGenPrepare::OptimizeBlock(BasicBlock &BB, bool& ModifiedDT) {
   return MadeChange;
 }
 
 // llvm.dbg.value is far away from the value then iSel may not be able
 // handle it properly. iSel will drop llvm.dbg.value if it can not
 // find a node corresponding to the value.
 bool CodeGenPrepare::PlaceDbgValues(Function &F) {
   bool MadeChange = false;
-  for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
+  for (BasicBlock &BB : F) {
     Instruction *PrevNonDbgInst = nullptr;
-    for (BasicBlock::iterator BI = I->begin(), BE = I->end(); BI != BE;) {
+    for (BasicBlock::iterator BI = BB.begin(), BE = BB.end(); BI != BE;) {
       Instruction *Insn = BI; ++BI;
       DbgValueInst *DVI = dyn_cast<DbgValueInst>(Insn);
       // Leave dbg.values that refer to an alloca alone. These
       // instrinsics describe the address of a variable (= the alloca)
       // being taken.  They should not be moved next to the alloca
       // (and to the beginning of the scope), but rather stay close to
       // where said address is used.
       if (!DVI || (DVI->getValue() && isa<AllocaInst>(DVI->getValue()))) {