[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. =]

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203364 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 3 insertions, 4 deletions

diff --git a/lib/Transforms/Scalar/Sink.cpp b/lib/Transforms/Scalar/Sink.cpp
index 643a5957cf..5e1e4564bb 100644
--- a/lib/Transforms/Scalar/Sink.cpp
+++ b/lib/Transforms/Scalar/Sink.cpp
@@ -76,15 +76,14 @@ bool Sinking::AllUsesDominatedByBlock(Instruction *Inst,
   // This may leave a referencing dbg_value in the original block, before
   // the definition of the vreg.  Dwarf generator handles this although the
   // user might not get the right info at runtime.
-  for (Value::use_iterator I = Inst->use_begin(),
-       E = Inst->use_end(); I != E; ++I) {
+  for (Use &U : Inst->uses()) {
     // Determine the block of the use.
-    Instruction *UseInst = cast<Instruction>(*I);
+    Instruction *UseInst = cast<Instruction>(U.getUser());
     BasicBlock *UseBlock = UseInst->getParent();
     if (PHINode *PN = dyn_cast<PHINode>(UseInst)) {
       // PHI nodes use the operand in the predecessor block, not the block with
       // the PHI.
-      unsigned Num = PHINode::getIncomingValueNumForOperand(I.getOperandNo());
+      unsigned Num = PHINode::getIncomingValueNumForOperand(U.getOperandNo());
       UseBlock = PN->getIncomingBlock(Num);
     }
     // Check that it dominates.