[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, 5 deletions

diff --git a/llvm/lib/IR/Instruction.cpp b/llvm/lib/IR/Instruction.cpp
index 4bcf7484d67..67aa8b28183 100644
--- a/llvm/lib/IR/Instruction.cpp
+++ b/llvm/lib/IR/Instruction.cpp
@@ -403,18 +403,18 @@ bool Instruction::isSameOperationAs(const Instruction *I,
 /// specified block.  Note that PHI nodes are considered to evaluate their
 /// operands in the corresponding predecessor block.
 bool Instruction::isUsedOutsideOfBlock(const BasicBlock *BB) const {
-  for (const_use_iterator UI = use_begin(), E = use_end(); UI != E; ++UI) {
+  for (const Use &U : uses()) {
     // PHI nodes uses values in the corresponding predecessor block.  For other
     // instructions, just check to see whether the parent of the use matches up.
-    const User *U = *UI;
-    const PHINode *PN = dyn_cast<PHINode>(U);
+    const Instruction *I = cast<Instruction>(U.getUser());
+    const PHINode *PN = dyn_cast<PHINode>(I);
     if (PN == 0) {
-      if (cast<Instruction>(U)->getParent() != BB)
+      if (I->getParent() != BB)
         return true;
       continue;
     }
 
-    if (PN->getIncomingBlock(UI) != BB)
+    if (PN->getIncomingBlock(U) != BB)
       return true;
   }
   return false;