[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, 18 insertions, 20 deletions

diff --git a/llvm/lib/Transforms/Scalar/SCCP.cpp b/llvm/lib/Transforms/Scalar/SCCP.cpp
index 1159399275f..39e34657ad9 100644
--- a/llvm/lib/Transforms/Scalar/SCCP.cpp
+++ b/llvm/lib/Transforms/Scalar/SCCP.cpp
@@ -1181,10 +1181,9 @@ void SCCPSolver::Solve() {
       // since all of its users will have already been marked as overdefined
       // Update all of the users of this instruction's value.
       //
-      for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
-           UI != E; ++UI)
-        if (Instruction *I = dyn_cast<Instruction>(*UI))
-          OperandChangedState(I);
+      for (User *U : I->users())
+        if (Instruction *UI = dyn_cast<Instruction>(U))
+          OperandChangedState(UI);
     }
 
     // Process the instruction work list.
@@ -1201,10 +1200,9 @@ void SCCPSolver::Solve() {
       // Update all of the users of this instruction's value.
       //
       if (I->getType()->isStructTy() || !getValueState(I).isOverdefined())
-        for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
-             UI != E; ++UI)
-          if (Instruction *I = dyn_cast<Instruction>(*UI))
-            OperandChangedState(I);
+        for (User *U : I->users())
+          if (Instruction *UI = dyn_cast<Instruction>(U))
+            OperandChangedState(UI);
     }
 
     // Process the basic block work list.
@@ -1662,21 +1660,20 @@ static bool AddressIsTaken(const GlobalValue *GV) {
   // Delete any dead constantexpr klingons.
   GV->removeDeadConstantUsers();
 
-  for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
-       UI != E; ++UI) {
-    const User *U = *UI;
-    if (const StoreInst *SI = dyn_cast<StoreInst>(U)) {
+  for (const Use &U : GV->uses()) {
+    const User *UR = U.getUser();
+    if (const StoreInst *SI = dyn_cast<StoreInst>(UR)) {
       if (SI->getOperand(0) == GV || SI->isVolatile())
         return true;  // Storing addr of GV.
-    } else if (isa<InvokeInst>(U) || isa<CallInst>(U)) {
+    } else if (isa<InvokeInst>(UR) || isa<CallInst>(UR)) {
       // Make sure we are calling the function, not passing the address.
-      ImmutableCallSite CS(cast<Instruction>(U));
-      if (!CS.isCallee(UI))
+      ImmutableCallSite CS(cast<Instruction>(UR));
+      if (!CS.isCallee(&U))
         return true;
-    } else if (const LoadInst *LI = dyn_cast<LoadInst>(U)) {
+    } else if (const LoadInst *LI = dyn_cast<LoadInst>(UR)) {
       if (LI->isVolatile())
         return true;
-    } else if (isa<BlockAddress>(U)) {
+    } else if (isa<BlockAddress>(UR)) {
       // blockaddress doesn't take the address of the function, it takes addr
       // of label.
     } else {
@@ -1839,8 +1836,9 @@ bool IPSCCP::runOnModule(Module &M) {
     for (unsigned i = 0, e = BlocksToErase.size(); i != e; ++i) {
       // If there are any PHI nodes in this successor, drop entries for BB now.
       BasicBlock *DeadBB = BlocksToErase[i];
-      for (Value::use_iterator UI = DeadBB->use_begin(), UE = DeadBB->use_end();
-           UI != UE; ) {
+      for (Value::user_iterator UI = DeadBB->user_begin(),
+                                UE = DeadBB->user_end();
+           UI != UE;) {
         // Grab the user and then increment the iterator early, as the user
         // will be deleted. Step past all adjacent uses from the same user.
         Instruction *I = dyn_cast<Instruction>(*UI);
@@ -1930,7 +1928,7 @@ bool IPSCCP::runOnModule(Module &M) {
            "Overdefined values should have been taken out of the map!");
     DEBUG(dbgs() << "Found that GV '" << GV->getName() << "' is constant!\n");
     while (!GV->use_empty()) {
-      StoreInst *SI = cast<StoreInst>(GV->use_back());
+      StoreInst *SI = cast<StoreInst>(GV->user_back());
       SI->eraseFromParent();
     }
     M.getGlobalList().erase(GV);