[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/Transforms/IPO/StripSymbols.cpp b/llvm/lib/Transforms/IPO/StripSymbols.cpp
index 2ff2a987c54..33c834058c3 100644
--- a/llvm/lib/Transforms/IPO/StripSymbols.cpp
+++ b/llvm/lib/Transforms/IPO/StripSymbols.cpp
@@ -132,11 +132,10 @@ ModulePass *llvm::createStripDeadDebugInfoPass() {
 
 /// OnlyUsedBy - Return true if V is only used by Usr.
 static bool OnlyUsedBy(Value *V, Value *Usr) {
-  for(Value::use_iterator I = V->use_begin(), E = V->use_end(); I != E; ++I) {
-    User *U = *I;
+  for (User *U : V->users())
     if (U != Usr)
       return false;
-  }
+
   return true;
 }
 
@@ -250,7 +249,7 @@ bool StripDebugDeclare::runOnModule(Module &M) {
 
   if (Declare) {
     while (!Declare->use_empty()) {
-      CallInst *CI = cast<CallInst>(Declare->use_back());
+      CallInst *CI = cast<CallInst>(Declare->user_back());
       Value *Arg1 = CI->getArgOperand(0);
       Value *Arg2 = CI->getArgOperand(1);
       assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");