[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/Inliner.cpp b/llvm/lib/Transforms/IPO/Inliner.cpp
index bc78f22b442..e97fb834f8d 100644
--- a/llvm/lib/Transforms/IPO/Inliner.cpp
+++ b/llvm/lib/Transforms/IPO/Inliner.cpp
@@ -344,9 +344,8 @@ bool Inliner::shouldInline(CallSite CS) {
     bool callerWillBeRemoved = Caller->hasLocalLinkage();
     // This bool tracks what happens if we DO inline C into B.
     bool inliningPreventsSomeOuterInline = false;
-    for (Value::use_iterator I = Caller->use_begin(), E =Caller->use_end(); 
-         I != E; ++I) {
-      CallSite CS2(*I);
+    for (User *U : Caller->users()) {
+      CallSite CS2(U);
 
       // If this isn't a call to Caller (it could be some other sort
       // of reference) skip it.  Such references will prevent the caller
@@ -377,7 +376,7 @@ bool Inliner::shouldInline(CallSite CS) {
     // one is set very low by getInlineCost, in anticipation that Caller will
     // be removed entirely.  We did not account for this above unless there
     // is only one caller of Caller.
-    if (callerWillBeRemoved && Caller->use_begin() != Caller->use_end())
+    if (callerWillBeRemoved && !Caller->use_empty())
       TotalSecondaryCost += InlineConstants::LastCallToStaticBonus;
 
     if (inliningPreventsSomeOuterInline && TotalSecondaryCost < IC.getCost()) {