[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, 3 insertions, 4 deletions

diff --git a/llvm/lib/Analysis/IVUsers.cpp b/llvm/lib/Analysis/IVUsers.cpp
index 9f77c95aad2..7eade544578 100644
--- a/llvm/lib/Analysis/IVUsers.cpp
+++ b/llvm/lib/Analysis/IVUsers.cpp
@@ -142,9 +142,8 @@ bool IVUsers::AddUsersImpl(Instruction *I,
     return false;
 
   SmallPtrSet<Instruction *, 4> UniqueUsers;
-  for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
-       UI != E; ++UI) {
-    Instruction *User = cast<Instruction>(*UI);
+  for (Use &U : I->uses()) {
+    Instruction *User = cast<Instruction>(U.getUser());
     if (!UniqueUsers.insert(User))
       continue;
 
@@ -157,7 +156,7 @@ bool IVUsers::AddUsersImpl(Instruction *I,
     BasicBlock *UseBB = User->getParent();
     // A phi's use is live out of its predecessor block.
     if (PHINode *PHI = dyn_cast<PHINode>(User)) {
-      unsigned OperandNo = UI.getOperandNo();
+      unsigned OperandNo = U.getOperandNo();
       unsigned ValNo = PHINode::getIncomingValueNumForOperand(OperandNo);
       UseBB = PHI->getIncomingBlock(ValNo);
     }