[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/Scalar/ConstantHoisting.cpp b/llvm/lib/Transforms/Scalar/ConstantHoisting.cpp
index b4419313b06..6cfcec547d0 100644
--- a/llvm/lib/Transforms/Scalar/ConstantHoisting.cpp
+++ b/llvm/lib/Transforms/Scalar/ConstantHoisting.cpp
@@ -266,12 +266,11 @@ static void CollectBasicBlocks(SmallPtrSet<BasicBlock *, 4> &BBs, Function &F,
     BBs.insert(I->getParent());
   else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U))
     // Find all users of this constant expression.
-    for (Value::use_iterator UU = CE->use_begin(), E = CE->use_end();
-         UU != E; ++UU)
+    for (User *UU : CE->users())
       // Only record users that are instructions. We don't want to go down a
       // nested constant expression chain. Also check if the instruction is even
       // in the current function.
-      if (Instruction *I = dyn_cast<Instruction>(*UU))
+      if (Instruction *I = dyn_cast<Instruction>(UU))
         if(I->getParent()->getParent() == &F)
           BBs.insert(I->getParent());
 }
@@ -350,12 +349,11 @@ void ConstantHoisting::EmitBaseConstants(Function &F, User *U,
   ConstantExpr *CE = cast<ConstantExpr>(U);
   SmallVector<std::pair<Instruction *, Instruction *>, 8> WorkList;
   DEBUG(dbgs() << "Visit ConstantExpr " << *CE << '\n');
-  for (Value::use_iterator UU = CE->use_begin(), E = CE->use_end();
-       UU != E; ++UU) {
+  for (User *UU : CE->users()) {
     DEBUG(dbgs() << "Check user "; UU->print(dbgs()); dbgs() << '\n');
     // We only handel instructions here and won't walk down a ConstantExpr chain
     // to replace all ConstExpr with instructions.
-    if (Instruction *I = dyn_cast<Instruction>(*UU)) {
+    if (Instruction *I = dyn_cast<Instruction>(UU)) {
       // Only update constant expressions in the current function.
       if (I->getParent()->getParent() != &F) {
         DEBUG(dbgs() << "Not in the same function - skip.\n");
@@ -423,9 +421,9 @@ bool ConstantHoisting::EmitBaseConstants(Function &F) {
 
     // Use the same debug location as the last user of the constant.
     assert(!Base->use_empty() && "The use list is empty!?");
-    assert(isa<Instruction>(Base->use_back()) &&
+    assert(isa<Instruction>(Base->user_back()) &&
            "All uses should be instructions.");
-    Base->setDebugLoc(cast<Instruction>(Base->use_back())->getDebugLoc());
+    Base->setDebugLoc(cast<Instruction>(Base->user_back())->getDebugLoc());
 
     // Correct for base constant, which we counted above too.
     NumConstantsRebased--;