[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, 8 deletions

diff --git a/lib/Target/XCore/XCoreLowerThreadLocal.cpp b/lib/Target/XCore/XCoreLowerThreadLocal.cpp
index f9a8299fd3..b398c2d2f8 100644
--- a/lib/Target/XCore/XCoreLowerThreadLocal.cpp
+++ b/lib/Target/XCore/XCoreLowerThreadLocal.cpp
@@ -127,10 +127,7 @@ createReplacementInstr(ConstantExpr *CE, Instruction *Instr) {
 
 static bool replaceConstantExprOp(ConstantExpr *CE, Pass *P) {
   do {
-    SmallVector<WeakVH,8> WUsers;
-    for (Value::use_iterator I = CE->use_begin(), E = CE->use_end();
-         I != E; ++I)
-      WUsers.push_back(WeakVH(*I));
+    SmallVector<WeakVH,8> WUsers(CE->user_begin(), CE->user_end());
     std::sort(WUsers.begin(), WUsers.end());
     WUsers.erase(std::unique(WUsers.begin(), WUsers.end()), WUsers.end());
     while (!WUsers.empty())
@@ -162,9 +159,9 @@ static bool replaceConstantExprOp(ConstantExpr *CE, Pass *P) {
 
 static bool rewriteNonInstructionUses(GlobalVariable *GV, Pass *P) {
   SmallVector<WeakVH,8> WUsers;
-  for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I)
-    if (!isa<Instruction>(*I))
-      WUsers.push_back(WeakVH(*I));
+  for (User *U : GV->users())
+    if (!isa<Instruction>(U))
+      WUsers.push_back(WeakVH(U));
   while (!WUsers.empty())
     if (WeakVH WU = WUsers.pop_back_val()) {
       ConstantExpr *CE = dyn_cast<ConstantExpr>(WU);
@@ -203,7 +200,7 @@ bool XCoreLowerThreadLocal::lowerGlobal(GlobalVariable *GV) {
                        GV->isExternallyInitialized());
 
   // Update uses.
-  SmallVector<User *, 16> Users(GV->use_begin(), GV->use_end());
+  SmallVector<User *, 16> Users(GV->user_begin(), GV->user_end());
   for (unsigned I = 0, E = Users.size(); I != E; ++I) {
     User *U = Users[I];
     Instruction *Inst = cast<Instruction>(U);