[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, 6 deletions

diff --git a/tools/opt/AnalysisWrappers.cpp b/tools/opt/AnalysisWrappers.cpp
index 1774ea0295..4bdc268f8d 100644
--- a/tools/opt/AnalysisWrappers.cpp
+++ b/tools/opt/AnalysisWrappers.cpp
@@ -37,12 +37,11 @@ namespace {
         if (!I->isDeclaration()) continue;
 
         bool PrintedFn = false;
-        for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
-             UI != E; ++UI) {
-          Instruction *User = dyn_cast<Instruction>(*UI);
-          if (!User) continue;
+        for (User *U : I->users()) {
+          Instruction *UI = dyn_cast<Instruction>(U);
+          if (!UI) continue;
 
-          CallSite CS(cast<Value>(User));
+          CallSite CS(cast<Value>(UI));
           if (!CS) continue;
 
           for (CallSite::arg_iterator AI = CS.arg_begin(),
@@ -53,7 +52,7 @@ namespace {
               errs() << "Function '" << I->getName() << "':\n";
               PrintedFn = true;
             }
-            errs() << *User;
+            errs() << *UI;
             break;
           }
         }