[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, 10 insertions, 10 deletions

diff --git a/lib/IR/Function.cpp b/lib/IR/Function.cpp
index 72f38c5475..865970c469 100644
--- a/lib/IR/Function.cpp
+++ b/lib/IR/Function.cpp
@@ -711,15 +711,15 @@ Function *Intrinsic::getDeclaration(Module *M, ID id, ArrayRef<Type*> Tys) {
 /// hasAddressTaken - returns true if there are any uses of this function
 /// other than direct calls or invokes to it.
 bool Function::hasAddressTaken(const User* *PutOffender) const {
-  for (Value::const_use_iterator I = use_begin(), E = use_end(); I != E; ++I) {
-    const User *U = *I;
-    if (isa<BlockAddress>(U))
+  for (const Use &U : uses()) {
+    const User *FU = U.getUser();
+    if (isa<BlockAddress>(FU))
       continue;
-    if (!isa<CallInst>(U) && !isa<InvokeInst>(U))
-      return PutOffender ? (*PutOffender = U, true) : true;
-    ImmutableCallSite CS(cast<Instruction>(U));
-    if (!CS.isCallee(I))
-      return PutOffender ? (*PutOffender = U, true) : true;
+    if (!isa<CallInst>(FU) && !isa<InvokeInst>(FU))
+      return PutOffender ? (*PutOffender = FU, true) : true;
+    ImmutableCallSite CS(cast<Instruction>(FU));
+    if (!CS.isCallee(&U))
+      return PutOffender ? (*PutOffender = FU, true) : true;
   }
   return false;
 }
@@ -731,8 +731,8 @@ bool Function::isDefTriviallyDead() const {
     return false;
 
   // Check if the function is used by anything other than a blockaddress.
-  for (Value::const_use_iterator I = use_begin(), E = use_end(); I != E; ++I)
-    if (!isa<BlockAddress>(*I))
+  for (const User *U : users())
+    if (!isa<BlockAddress>(U))
       return false;
 
   return true;