[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, 5 insertions, 7 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 95225f428bd..f3602675ed0 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -788,15 +788,14 @@ static IntrinsicInst *FindInitTrampolineFromAlloca(Value *TrampMem) {
   // is good enough in practice and simpler than handling any number of casts.
   Value *Underlying = TrampMem->stripPointerCasts();
   if (Underlying != TrampMem &&
-      (!Underlying->hasOneUse() || *Underlying->use_begin() != TrampMem))
+      (!Underlying->hasOneUse() || Underlying->user_back() != TrampMem))
     return 0;
   if (!isa<AllocaInst>(Underlying))
     return 0;
 
   IntrinsicInst *InitTrampoline = 0;
-  for (Value::use_iterator I = TrampMem->use_begin(), E = TrampMem->use_end();
-       I != E; I++) {
-    IntrinsicInst *II = dyn_cast<IntrinsicInst>(*I);
+  for (User *U : TrampMem->users()) {
+    IntrinsicInst *II = dyn_cast<IntrinsicInst>(U);
     if (!II)
       return 0;
     if (II->getIntrinsicID() == Intrinsic::init_trampoline) {
@@ -1010,9 +1009,8 @@ bool InstCombiner::transformConstExprCastCall(CallSite CS) {
     // the critical edge).  Bail out in this case.
     if (!Caller->use_empty())
       if (InvokeInst *II = dyn_cast<InvokeInst>(Caller))
-        for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
-             UI != E; ++UI)
-          if (PHINode *PN = dyn_cast<PHINode>(*UI))
+        for (User *U : II->users())
+          if (PHINode *PN = dyn_cast<PHINode>(U))
             if (PN->getParent() == II->getNormalDest() ||
                 PN->getParent() == II->getUnwindDest())
               return false;