[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, 7 insertions, 8 deletions

diff --git a/lib/CodeGen/SjLjEHPrepare.cpp b/lib/CodeGen/SjLjEHPrepare.cpp
index e4ddb7bf20..dc7ca2bd54 100644
--- a/lib/CodeGen/SjLjEHPrepare.cpp
+++ b/lib/CodeGen/SjLjEHPrepare.cpp
@@ -149,7 +149,7 @@ static void MarkBlocksLiveIn(BasicBlock *BB,
 /// instruction with those returned by the personality function.
 void SjLjEHPrepare::substituteLPadValues(LandingPadInst *LPI, Value *ExnVal,
                                          Value *SelVal) {
-  SmallVector<Value *, 8> UseWorkList(LPI->use_begin(), LPI->use_end());
+  SmallVector<Value *, 8> UseWorkList(LPI->user_begin(), LPI->user_end());
   while (!UseWorkList.empty()) {
     Value *Val = UseWorkList.pop_back_val();
     ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(Val);
@@ -294,8 +294,8 @@ void SjLjEHPrepare::lowerAcrossUnwindEdges(Function &F,
       if (Inst->use_empty())
         continue;
       if (Inst->hasOneUse() &&
-          cast<Instruction>(Inst->use_back())->getParent() == BB &&
-          !isa<PHINode>(Inst->use_back()))
+          cast<Instruction>(Inst->user_back())->getParent() == BB &&
+          !isa<PHINode>(Inst->user_back()))
         continue;
 
       // If this is an alloca in the entry block, it's not a real register
@@ -306,11 +306,10 @@ void SjLjEHPrepare::lowerAcrossUnwindEdges(Function &F,
 
       // Avoid iterator invalidation by copying users to a temporary vector.
       SmallVector<Instruction *, 16> Users;
-      for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
-           UI != E; ++UI) {
-        Instruction *User = cast<Instruction>(*UI);
-        if (User->getParent() != BB || isa<PHINode>(User))
-          Users.push_back(User);
+      for (User *U : Inst->users()) {
+        Instruction *UI = cast<Instruction>(U);
+        if (UI->getParent() != BB || isa<PHINode>(UI))
+          Users.push_back(UI);
       }
 
       // Find all of the blocks that this value is live in.