[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, 6 insertions, 8 deletions

diff --git a/llvm/lib/Transforms/Utils/InlineFunction.cpp b/llvm/lib/Transforms/Utils/InlineFunction.cpp
index ae3bf6f2c6d..86def3e48e9 100644
--- a/llvm/lib/Transforms/Utils/InlineFunction.cpp
+++ b/llvm/lib/Transforms/Utils/InlineFunction.cpp
@@ -401,9 +401,8 @@ static Value *HandleByValArgument(Value *Arg, Instruction *TheCall,
 // isUsedByLifetimeMarker - Check whether this Value is used by a lifetime
 // intrinsic.
 static bool isUsedByLifetimeMarker(Value *V) {
-  for (Value::use_iterator UI = V->use_begin(), UE = V->use_end(); UI != UE;
-       ++UI) {
-    if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(*UI)) {
+  for (User *U : V->users()) {
+    if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U)) {
       switch (II->getIntrinsicID()) {
       default: break;
       case Intrinsic::lifetime_start:
@@ -423,11 +422,10 @@ static bool hasLifetimeMarkers(AllocaInst *AI) {
     return isUsedByLifetimeMarker(AI);
 
   // Do a scan to find all the casts to i8*.
-  for (Value::use_iterator I = AI->use_begin(), E = AI->use_end(); I != E;
-       ++I) {
-    if (I->getType() != Int8PtrTy) continue;
-    if (I->stripPointerCasts() != AI) continue;
-    if (isUsedByLifetimeMarker(*I))
+  for (User *U : AI->users()) {
+    if (U->getType() != Int8PtrTy) continue;
+    if (U->stripPointerCasts() != AI) continue;
+    if (isUsedByLifetimeMarker(U))
       return true;
   }
   return false;