[C++11] Add range based accessors for the Use-Def chain of a Value.

This requires a number of steps.
1) Move value_use_iterator into the Value class as an implementation
   detail
2) Change it to actually be a *Use* iterator rather than a *User*
   iterator.
3) Add an adaptor which is a User iterator that always looks through the
   Use to the User.
4) Wrap these in Value::use_iterator and Value::user_iterator typedefs.
5) Add the range adaptors as Value::uses() and Value::users().
6) Update *all* of the callers to correctly distinguish between whether
   they wanted a use_iterator (and to explicitly dig out the User when
   needed), or a user_iterator which makes the Use itself totally
   opaque.

Because #6 requires churning essentially everything that walked the
Use-Def chains, I went ahead and added all of the range adaptors and
switched them to range-based loops where appropriate. Also because the
renaming requires at least churning every line of code, it didn't make
any sense to split these up into multiple commits -- all of which would
touch all of the same lies of code.

The result is still not quite optimal. The Value::use_iterator is a nice
regular iterator, but Value::user_iterator is an iterator over User*s
rather than over the User objects themselves. As a consequence, it fits
a bit awkwardly into the range-based world and it has the weird
extra-dereferencing 'operator->' that so many of our iterators have.
I think this could be fixed by providing something which transforms
a range of T&s into a range of T*s, but that *can* be separated into
another patch, and it isn't yet 100% clear whether this is the right
move.

However, this change gets us most of the benefit and cleans up
a substantial amount of code around Use and User. =]

llvm-svn: 203364

1 files changed, 10 insertions, 13 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
index f6b9ab7e40c..30f56be4d05 100644
--- a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
@@ -285,15 +285,14 @@ Instruction *SimplifyIndvar::splitOverflowIntrinsic(Instruction *IVUser,
   // Find a branch guarded by the overflow check.
   BranchInst *Branch = 0;
   Instruction *AddVal = 0;
-  for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
-       UI != E; ++UI) {
-    if (ExtractValueInst *ExtractInst = dyn_cast<ExtractValueInst>(*UI)) {
+  for (User *U : II->users()) {
+    if (ExtractValueInst *ExtractInst = dyn_cast<ExtractValueInst>(U)) {
       if (ExtractInst->getNumIndices() != 1)
         continue;
       if (ExtractInst->getIndices()[0] == 0)
         AddVal = ExtractInst;
       else if (ExtractInst->getIndices()[0] == 1 && ExtractInst->hasOneUse())
-        Branch = dyn_cast<BranchInst>(ExtractInst->use_back());
+        Branch = dyn_cast<BranchInst>(ExtractInst->user_back());
     }
   }
   if (!AddVal || !Branch)
@@ -305,12 +304,11 @@ Instruction *SimplifyIndvar::splitOverflowIntrinsic(Instruction *IVUser,
 
   // Check if all users of the add are provably NSW.
   bool AllNSW = true;
-  for (Value::use_iterator UI = AddVal->use_begin(), E = AddVal->use_end();
-       UI != E; ++UI) {
-    if (Instruction *UseInst = dyn_cast<Instruction>(*UI)) {
+  for (Use &U : AddVal->uses()) {
+    if (Instruction *UseInst = dyn_cast<Instruction>(U.getUser())) {
       BasicBlock *UseBB = UseInst->getParent();
       if (PHINode *PHI = dyn_cast<PHINode>(UseInst))
-        UseBB = PHI->getIncomingBlock(UI);
+        UseBB = PHI->getIncomingBlock(U);
       if (!DT->dominates(ContinueBB, UseBB)) {
         AllNSW = false;
         break;
@@ -343,16 +341,15 @@ static void pushIVUsers(
   SmallPtrSet<Instruction*,16> &Simplified,
   SmallVectorImpl< std::pair<Instruction*,Instruction*> > &SimpleIVUsers) {
 
-  for (Value::use_iterator UI = Def->use_begin(), E = Def->use_end();
-       UI != E; ++UI) {
-    Instruction *User = cast<Instruction>(*UI);
+  for (User *U : Def->users()) {
+    Instruction *UI = cast<Instruction>(U);
 
     // Avoid infinite or exponential worklist processing.
     // Also ensure unique worklist users.
     // If Def is a LoopPhi, it may not be in the Simplified set, so check for
     // self edges first.
-    if (User != Def && Simplified.insert(User))
-      SimpleIVUsers.push_back(std::make_pair(User, Def));
+    if (UI != Def && Simplified.insert(UI))
+      SimpleIVUsers.push_back(std::make_pair(UI, Def));
   }
 }