[C++11] Add predecessors(BasicBlock *) / successors(BasicBlock *) iterator ranges.

Summary: This patch introduces two new iterator ranges and updates existing code to use it.  No functional change intended.

Test Plan: All tests (make check-all) still pass.

Reviewers: dblaikie

Reviewed By: dblaikie

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D4481

llvm-svn: 213474

1 files changed, 10 insertions, 21 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopSimplify.cpp b/llvm/lib/Transforms/Utils/LoopSimplify.cpp
index ef422914b6b..faab7725855 100644
--- a/llvm/lib/Transforms/Utils/LoopSimplify.cpp
+++ b/llvm/lib/Transforms/Utils/LoopSimplify.cpp
@@ -114,9 +114,7 @@ BasicBlock *llvm::InsertPreheaderForLoop(Loop *L, Pass *PP) {
 
   // Compute the set of predecessors of the loop that are not in the loop.
   SmallVector<BasicBlock*, 8> OutsideBlocks;
-  for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header);
-       PI != PE; ++PI) {
-    BasicBlock *P = *PI;
+  for (BasicBlock *P : predecessors(Header)) {
     if (!L->contains(P)) {         // Coming in from outside the loop?
       // If the loop is branched to from an indirect branch, we won't
       // be able to fully transform the loop, because it prohibits
@@ -158,8 +156,7 @@ BasicBlock *llvm::InsertPreheaderForLoop(Loop *L, Pass *PP) {
 /// the loop.
 static BasicBlock *rewriteLoopExitBlock(Loop *L, BasicBlock *Exit, Pass *PP) {
   SmallVector<BasicBlock*, 8> LoopBlocks;
-  for (pred_iterator I = pred_begin(Exit), E = pred_end(Exit); I != E; ++I) {
-    BasicBlock *P = *I;
+  for (BasicBlock *P : predecessors(Exit)) {
     if (L->contains(P)) {
       // Don't do this if the loop is exited via an indirect branch.
       if (isa<IndirectBrInst>(P->getTerminator())) return nullptr;
@@ -199,10 +196,8 @@ static void addBlockAndPredsToSet(BasicBlock *InputBB, BasicBlock *StopBlock,
     if (Blocks.insert(BB).second && BB != StopBlock)
       // If BB is not already processed and it is not a stop block then
       // insert its predecessor in the work list
-      for (pred_iterator I = pred_begin(BB), E = pred_end(BB); I != E; ++I) {
-        BasicBlock *WBB = *I;
+      for (BasicBlock *WBB : predecessors(BB))
         Worklist.push_back(WBB);
-      }
   } while (!Worklist.empty());
 }
 
@@ -316,8 +311,7 @@ static Loop *separateNestedLoop(Loop *L, BasicBlock *Preheader,
   // Determine which blocks should stay in L and which should be moved out to
   // the Outer loop now.
   std::set<BasicBlock*> BlocksInL;
-  for (pred_iterator PI=pred_begin(Header), E = pred_end(Header); PI!=E; ++PI) {
-    BasicBlock *P = *PI;
+  for (BasicBlock *P : predecessors(Header)) {
     if (DT->dominates(Header, P))
       addBlockAndPredsToSet(P, Header, BlocksInL);
   }
@@ -371,9 +365,7 @@ static BasicBlock *insertUniqueBackedgeBlock(Loop *L, BasicBlock *Preheader,
 
   // Figure out which basic blocks contain back-edges to the loop header.
   std::vector<BasicBlock*> BackedgeBlocks;
-  for (pred_iterator I = pred_begin(Header), E = pred_end(Header); I != E; ++I){
-    BasicBlock *P = *I;
-
+  for (BasicBlock *P : predecessors(Header)) {
     // Indirectbr edges cannot be split, so we must fail if we find one.
     if (isa<IndirectBrInst>(P->getTerminator()))
       return nullptr;
@@ -488,9 +480,7 @@ ReprocessLoop:
     if (*BB == L->getHeader()) continue;
 
     SmallPtrSet<BasicBlock*, 4> BadPreds;
-    for (pred_iterator PI = pred_begin(*BB),
-         PE = pred_end(*BB); PI != PE; ++PI) {
-      BasicBlock *P = *PI;
+    for (BasicBlock *P : predecessors(*BB)) {
       if (!L->contains(P))
         BadPreds.insert(P);
     }
@@ -503,8 +493,8 @@ ReprocessLoop:
                    << (*I)->getName() << "\n");
 
       // Inform each successor of each dead pred.
-      for (succ_iterator SI = succ_begin(*I), SE = succ_end(*I); SI != SE; ++SI)
-        (*SI)->removePredecessor(*I);
+      for (BasicBlock *Succ : successors(*I))
+        Succ->removePredecessor(*I);
       // Zap the dead pred's terminator and replace it with unreachable.
       TerminatorInst *TI = (*I)->getTerminator();
        TI->replaceAllUsesWith(UndefValue::get(TI->getType()));
@@ -561,11 +551,10 @@ ReprocessLoop:
   for (SmallSetVector<BasicBlock *, 8>::iterator I = ExitBlockSet.begin(),
          E = ExitBlockSet.end(); I != E; ++I) {
     BasicBlock *ExitBlock = *I;
-    for (pred_iterator PI = pred_begin(ExitBlock), PE = pred_end(ExitBlock);
-         PI != PE; ++PI)
+    for (BasicBlock *Pred : predecessors(ExitBlock))
       // Must be exactly this loop: no subloops, parent loops, or non-loop preds
       // allowed.
-      if (!L->contains(*PI)) {
+      if (!L->contains(Pred)) {
         if (rewriteLoopExitBlock(L, ExitBlock, PP)) {
           ++NumInserted;
           Changed = true;