[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

9 files changed, 34 insertions, 36 deletions

diff --git a/lib/IR/AutoUpgrade.cpp b/lib/IR/AutoUpgrade.cpp
index ca44143307..b7429b30f5 100644
--- a/lib/IR/AutoUpgrade.cpp
+++ b/lib/IR/AutoUpgrade.cpp
@@ -411,7 +411,7 @@ void llvm::UpgradeCallsToIntrinsic(Function* F) {
   if (UpgradeIntrinsicFunction(F, NewFn)) {
     if (NewFn != F) {
       // Replace all uses to the old function with the new one if necessary.
-      for (Value::use_iterator UI = F->use_begin(), UE = F->use_end();
+      for (Value::user_iterator UI = F->user_begin(), UE = F->user_end();
            UI != UE; ) {
         if (CallInst *CI = dyn_cast<CallInst>(*UI++))
           UpgradeIntrinsicCall(CI, NewFn);
diff --git a/lib/IR/BasicBlock.cpp b/lib/IR/BasicBlock.cpp
index ef264d27fc..3079f0ad08 100644
--- a/lib/IR/BasicBlock.cpp
+++ b/lib/IR/BasicBlock.cpp
@@ -74,7 +74,7 @@ BasicBlock::~BasicBlock() {
     Constant *Replacement =
       ConstantInt::get(llvm::Type::getInt32Ty(getContext()), 1);
     while (!use_empty()) {
-      BlockAddress *BA = cast<BlockAddress>(use_back());
+      BlockAddress *BA = cast<BlockAddress>(user_back());
       BA->replaceAllUsesWith(ConstantExpr::getIntToPtr(Replacement,
                                                        BA->getType()));
       BA->destroyConstant();
diff --git a/lib/IR/Constants.cpp b/lib/IR/Constants.cpp
index 944402558f..2a3a5fdf13 100644
--- a/lib/IR/Constants.cpp
+++ b/lib/IR/Constants.cpp
@@ -218,7 +218,7 @@ void Constant::destroyConstantImpl() {
   // Constants) that they are, in fact, invalid now and should be deleted.
   //
   while (!use_empty()) {
-    Value *V = use_back();
+    Value *V = user_back();
 #ifndef NDEBUG      // Only in -g mode...
     if (!isa<Constant>(V)) {
       dbgs() << "While deleting: " << *this
@@ -230,7 +230,7 @@ void Constant::destroyConstantImpl() {
     cast<Constant>(V)->destroyConstant();
 
     // The constant should remove itself from our use list...
-    assert((use_empty() || use_back() != V) && "Constant not removed!");
+    assert((use_empty() || user_back() != V) && "Constant not removed!");
   }
 
   // Value has no outstanding references it is safe to delete it now...
@@ -307,8 +307,8 @@ bool Constant::isThreadDependent() const {
 /// isConstantUsed - Return true if the constant has users other than constant
 /// exprs and other dangling things.
 bool Constant::isConstantUsed() const {
-  for (const_use_iterator UI = use_begin(), E = use_end(); UI != E; ++UI) {
-    const Constant *UC = dyn_cast<Constant>(*UI);
+  for (const User *U : users()) {
+    const Constant *UC = dyn_cast<Constant>(U);
     if (UC == 0 || isa<GlobalValue>(UC))
       return true;
 
@@ -377,7 +377,7 @@ static bool removeDeadUsersOfConstant(const Constant *C) {
   if (isa<GlobalValue>(C)) return false; // Cannot remove this
 
   while (!C->use_empty()) {
-    const Constant *User = dyn_cast<Constant>(C->use_back());
+    const Constant *User = dyn_cast<Constant>(C->user_back());
     if (!User) return false; // Non-constant usage;
     if (!removeDeadUsersOfConstant(User))
       return false; // Constant wasn't dead
@@ -393,8 +393,8 @@ static bool removeDeadUsersOfConstant(const Constant *C) {
 /// that want to check to see if a global is unused, but don't want to deal
 /// with potentially dead constants hanging off of the globals.
 void Constant::removeDeadConstantUsers() const {
-  Value::const_use_iterator I = use_begin(), E = use_end();
-  Value::const_use_iterator LastNonDeadUser = E;
+  Value::const_user_iterator I = user_begin(), E = user_end();
+  Value::const_user_iterator LastNonDeadUser = E;
   while (I != E) {
     const Constant *User = dyn_cast<Constant>(*I);
     if (User == 0) {
@@ -413,7 +413,7 @@ void Constant::removeDeadConstantUsers() const {
 
     // If the constant was dead, then the iterator is invalidated.
     if (LastNonDeadUser == E) {
-      I = use_begin();
+      I = user_begin();
       if (I == E) break;
     } else {
       I = LastNonDeadUser;
diff --git a/lib/IR/Core.cpp b/lib/IR/Core.cpp
index 6c012736de..0c2e31a0b0 100644
--- a/lib/IR/Core.cpp
+++ b/lib/IR/Core.cpp
@@ -514,7 +514,7 @@ LLVMUseRef LLVMGetFirstUse(LLVMValueRef Val) {
   Value::use_iterator I = V->use_begin();
   if (I == V->use_end())
     return 0;
-  return wrap(&(I.getUse()));
+  return wrap(&*I);
 }
 
 LLVMUseRef LLVMGetNextUse(LLVMUseRef U) {
diff --git a/lib/IR/DebugInfo.cpp b/lib/IR/DebugInfo.cpp
index 4e9d1d1c2e..d69138e057 100644
--- a/lib/IR/DebugInfo.cpp
+++ b/lib/IR/DebugInfo.cpp
@@ -1476,7 +1476,7 @@ bool llvm::StripDebugInfo(Module &M) {
   // the module.
   if (Function *Declare = M.getFunction("llvm.dbg.declare")) {
     while (!Declare->use_empty()) {
-      CallInst *CI = cast<CallInst>(Declare->use_back());
+      CallInst *CI = cast<CallInst>(Declare->user_back());
       CI->eraseFromParent();
     }
     Declare->eraseFromParent();
@@ -1485,7 +1485,7 @@ bool llvm::StripDebugInfo(Module &M) {
 
   if (Function *DbgVal = M.getFunction("llvm.dbg.value")) {
     while (!DbgVal->use_empty()) {
-      CallInst *CI = cast<CallInst>(DbgVal->use_back());
+      CallInst *CI = cast<CallInst>(DbgVal->user_back());
       CI->eraseFromParent();
     }
     DbgVal->eraseFromParent();
diff --git a/lib/IR/Function.cpp b/lib/IR/Function.cpp
index 72f38c5475..865970c469 100644
--- a/lib/IR/Function.cpp
+++ b/lib/IR/Function.cpp
@@ -711,15 +711,15 @@ Function *Intrinsic::getDeclaration(Module *M, ID id, ArrayRef<Type*> Tys) {
 /// hasAddressTaken - returns true if there are any uses of this function
 /// other than direct calls or invokes to it.
 bool Function::hasAddressTaken(const User* *PutOffender) const {
-  for (Value::const_use_iterator I = use_begin(), E = use_end(); I != E; ++I) {
-    const User *U = *I;
-    if (isa<BlockAddress>(U))
+  for (const Use &U : uses()) {
+    const User *FU = U.getUser();
+    if (isa<BlockAddress>(FU))
       continue;
-    if (!isa<CallInst>(U) && !isa<InvokeInst>(U))
-      return PutOffender ? (*PutOffender = U, true) : true;
-    ImmutableCallSite CS(cast<Instruction>(U));
-    if (!CS.isCallee(I))
-      return PutOffender ? (*PutOffender = U, true) : true;
+    if (!isa<CallInst>(FU) && !isa<InvokeInst>(FU))
+      return PutOffender ? (*PutOffender = FU, true) : true;
+    ImmutableCallSite CS(cast<Instruction>(FU));
+    if (!CS.isCallee(&U))
+      return PutOffender ? (*PutOffender = FU, true) : true;
   }
   return false;
 }
@@ -731,8 +731,8 @@ bool Function::isDefTriviallyDead() const {
     return false;
 
   // Check if the function is used by anything other than a blockaddress.
-  for (Value::const_use_iterator I = use_begin(), E = use_end(); I != E; ++I)
-    if (!isa<BlockAddress>(*I))
+  for (const User *U : users())
+    if (!isa<BlockAddress>(U))
       return false;
 
   return true;
diff --git a/lib/IR/Instruction.cpp b/lib/IR/Instruction.cpp
index 4bcf7484d6..67aa8b2818 100644
--- a/lib/IR/Instruction.cpp
+++ b/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;
diff --git a/lib/IR/Value.cpp b/lib/IR/Value.cpp
index bdb544bef4..97a562e3e5 100644
--- a/lib/IR/Value.cpp
+++ b/lib/IR/Value.cpp
@@ -119,7 +119,7 @@ bool Value::isUsedInBasicBlock(const BasicBlock *BB) const {
   // Scan both lists simultaneously until one is exhausted. This limits the
   // search to the shorter list.
   BasicBlock::const_iterator BI = BB->begin(), BE = BB->end();
-  const_use_iterator UI = use_begin(), UE = use_end();
+  const_user_iterator UI = user_begin(), UE = user_end();
   for (; BI != BE && UI != UE; ++BI, ++UI) {
     // Scan basic block: Check if this Value is used by the instruction at BI.
     if (std::find(BI->op_begin(), BI->op_end(), this) != BI->op_end())
diff --git a/lib/IR/Verifier.cpp b/lib/IR/Verifier.cpp
index deb708da17..f64ebc1a67 100644
--- a/lib/IR/Verifier.cpp
+++ b/lib/IR/Verifier.cpp
@@ -1974,9 +1974,8 @@ void Verifier::visitInstruction(Instruction &I) {
   Assert1(BB, "Instruction not embedded in basic block!", &I);
 
   if (!isa<PHINode>(I)) {   // Check that non-phi nodes are not self referential
-    for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
-         UI != UE; ++UI)
-      Assert1(*UI != (User*)&I || !DT.isReachableFromEntry(BB),
+    for (User *U : I.users())
+      Assert1(U != (User*)&I || !DT.isReachableFromEntry(BB),
               "Only PHI nodes may reference their own value!", &I);
   }
 
@@ -1999,13 +1998,12 @@ void Verifier::visitInstruction(Instruction &I) {
   // Check that all uses of the instruction, if they are instructions
   // themselves, actually have parent basic blocks.  If the use is not an
   // instruction, it is an error!
-  for (User::use_iterator UI = I.use_begin(), UE = I.use_end();
-       UI != UE; ++UI) {
-    if (Instruction *Used = dyn_cast<Instruction>(*UI))
+  for (Use &U : I.uses()) {
+    if (Instruction *Used = dyn_cast<Instruction>(U.getUser()))
       Assert2(Used->getParent() != 0, "Instruction referencing instruction not"
               " embedded in a basic block!", &I, Used);
     else {
-      CheckFailed("Use of instruction is not an instruction!", *UI);
+      CheckFailed("Use of instruction is not an instruction!", U);
       return;
     }
   }