[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, 5 insertions, 7 deletions

diff --git a/lib/IR/Verifier.cpp b/lib/IR/Verifier.cpp
index deb708da17..f64ebc1a67 100644
--- a/lib/IR/Verifier.cpp
+++ b/lib/IR/Verifier.cpp
@@ -1974,9 +1974,8 @@ void Verifier::visitInstruction(Instruction &I) {
   Assert1(BB, "Instruction not embedded in basic block!", &I);
 
   if (!isa<PHINode>(I)) {   // Check that non-phi nodes are not self referential
-    for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
-         UI != UE; ++UI)
-      Assert1(*UI != (User*)&I || !DT.isReachableFromEntry(BB),
+    for (User *U : I.users())
+      Assert1(U != (User*)&I || !DT.isReachableFromEntry(BB),
               "Only PHI nodes may reference their own value!", &I);
   }
 
@@ -1999,13 +1998,12 @@ void Verifier::visitInstruction(Instruction &I) {
   // Check that all uses of the instruction, if they are instructions
   // themselves, actually have parent basic blocks.  If the use is not an
   // instruction, it is an error!
-  for (User::use_iterator UI = I.use_begin(), UE = I.use_end();
-       UI != UE; ++UI) {
-    if (Instruction *Used = dyn_cast<Instruction>(*UI))
+  for (Use &U : I.uses()) {
+    if (Instruction *Used = dyn_cast<Instruction>(U.getUser()))
       Assert2(Used->getParent() != 0, "Instruction referencing instruction not"
               " embedded in a basic block!", &I, Used);
     else {
-      CheckFailed("Use of instruction is not an instruction!", *UI);
+      CheckFailed("Use of instruction is not an instruction!", U);
       return;
     }
   }