[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, 5 deletions

diff --git a/lib/Target/NVPTX/NVVMReflect.cpp b/lib/Target/NVPTX/NVVMReflect.cpp
index 5da8c2ed09..8b5444a66d 100644
--- a/lib/Target/NVPTX/NVVMReflect.cpp
+++ b/lib/Target/NVPTX/NVVMReflect.cpp
@@ -143,11 +143,9 @@ bool NVVMReflect::runOnModule(Module &M) {
   // ConstantArray can be found successfully, see if it can be
   // found in VarMap. If so, replace the uses of CallInst with the
   // value found in VarMap. If not, replace the use  with value 0.
-  for (Value::use_iterator I = ReflectFunction->use_begin(),
-                           E = ReflectFunction->use_end();
-       I != E; ++I) {
-    assert(isa<CallInst>(*I) && "Only a call instruction can use _reflect");
-    CallInst *Reflect = cast<CallInst>(*I);
+  for (User *U : ReflectFunction->users()) {
+    assert(isa<CallInst>(U) && "Only a call instruction can use _reflect");
+    CallInst *Reflect = cast<CallInst>(U);
 
     assert((Reflect->getNumOperands() == 2) &&
            "Only one operand expect for _reflect function");