[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, 24 insertions, 30 deletions

diff --git a/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp b/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
index fb458a3ef85..48d3fba54f4 100644
--- a/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
+++ b/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
@@ -136,11 +136,10 @@ CallGraphNode *ArgPromotion::PromoteArguments(CallGraphNode *CGN) {
   // transform functions that have indirect callers.  Also see if the function
   // is self-recursive.
   bool isSelfRecursive = false;
-  for (Value::use_iterator UI = F->use_begin(), E = F->use_end();
-       UI != E; ++UI) {
-    CallSite CS(*UI);
+  for (Use &U : F->uses()) {
+    CallSite CS(U.getUser());
     // Must be a direct call.
-    if (CS.getInstruction() == 0 || !CS.isCallee(UI)) return 0;
+    if (CS.getInstruction() == 0 || !CS.isCallee(&U)) return 0;
     
     if (CS.getInstruction()->getParent()->getParent() == F)
       isSelfRecursive = true;
@@ -222,9 +221,8 @@ static bool AllCallersPassInValidPointerForArgument(Argument *Arg) {
 
   // Look at all call sites of the function.  At this pointer we know we only
   // have direct callees.
-  for (Value::use_iterator UI = Callee->use_begin(), E = Callee->use_end();
-       UI != E; ++UI) {
-    CallSite CS(*UI);
+  for (User *U : Callee->users()) {
+    CallSite CS(U);
     assert(CS && "Should only have direct calls!");
 
     if (!CS.getArgument(ArgNo)->isDereferenceablePointer())
@@ -375,17 +373,16 @@ bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg,
   // not (GEP+)loads, or any (GEP+)loads that are not safe to promote.
   SmallVector<LoadInst*, 16> Loads;
   IndicesVector Operands;
-  for (Value::use_iterator UI = Arg->use_begin(), E = Arg->use_end();
-       UI != E; ++UI) {
-    User *U = *UI;
+  for (Use &U : Arg->uses()) {
+    User *UR = U.getUser();
     Operands.clear();
-    if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
+    if (LoadInst *LI = dyn_cast<LoadInst>(UR)) {
       // Don't hack volatile/atomic loads
       if (!LI->isSimple()) return false;
       Loads.push_back(LI);
       // Direct loads are equivalent to a GEP with a zero index and then a load.
       Operands.push_back(0);
-    } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
+    } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(UR)) {
       if (GEP->use_empty()) {
         // Dead GEP's cause trouble later.  Just remove them if we run into
         // them.
@@ -406,9 +403,8 @@ bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg,
           return false;  // Not a constant operand GEP!
 
       // Ensure that the only users of the GEP are load instructions.
-      for (Value::use_iterator UI = GEP->use_begin(), E = GEP->use_end();
-           UI != E; ++UI)
-        if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
+      for (User *GEPU : GEP->users())
+        if (LoadInst *LI = dyn_cast<LoadInst>(GEPU)) {
           // Don't hack volatile/atomic loads
           if (!LI->isSimple()) return false;
           Loads.push_back(LI);
@@ -554,16 +550,15 @@ CallGraphNode *ArgPromotion::DoPromotion(Function *F,
       // In this table, we will track which indices are loaded from the argument
       // (where direct loads are tracked as no indices).
       ScalarizeTable &ArgIndices = ScalarizedElements[I];
-      for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
-           ++UI) {
-        Instruction *User = cast<Instruction>(*UI);
-        assert(isa<LoadInst>(User) || isa<GetElementPtrInst>(User));
+      for (User *U : I->users()) {
+        Instruction *UI = cast<Instruction>(U);
+        assert(isa<LoadInst>(UI) || isa<GetElementPtrInst>(UI));
         IndicesVector Indices;
-        Indices.reserve(User->getNumOperands() - 1);
+        Indices.reserve(UI->getNumOperands() - 1);
         // Since loads will only have a single operand, and GEPs only a single
         // non-index operand, this will record direct loads without any indices,
         // and gep+loads with the GEP indices.
-        for (User::op_iterator II = User->op_begin() + 1, IE = User->op_end();
+        for (User::op_iterator II = UI->op_begin() + 1, IE = UI->op_end();
              II != IE; ++II)
           Indices.push_back(cast<ConstantInt>(*II)->getSExtValue());
         // GEPs with a single 0 index can be merged with direct loads
@@ -571,11 +566,11 @@ CallGraphNode *ArgPromotion::DoPromotion(Function *F,
           Indices.clear();
         ArgIndices.insert(Indices);
         LoadInst *OrigLoad;
-        if (LoadInst *L = dyn_cast<LoadInst>(User))
+        if (LoadInst *L = dyn_cast<LoadInst>(UI))
           OrigLoad = L;
         else
           // Take any load, we will use it only to update Alias Analysis
-          OrigLoad = cast<LoadInst>(User->use_back());
+          OrigLoad = cast<LoadInst>(UI->user_back());
         OriginalLoads[std::make_pair(I, Indices)] = OrigLoad;
       }
 
@@ -636,7 +631,7 @@ CallGraphNode *ArgPromotion::DoPromotion(Function *F,
   //
   SmallVector<Value*, 16> Args;
   while (!F->use_empty()) {
-    CallSite CS(F->use_back());
+    CallSite CS(F->user_back());
     assert(CS.getCalledFunction() == F);
     Instruction *Call = CS.getInstruction();
     const AttributeSet &CallPAL = CS.getAttributes();
@@ -815,9 +810,8 @@ CallGraphNode *ArgPromotion::DoPromotion(Function *F,
 
       // If the alloca is used in a call, we must clear the tail flag since
       // the callee now uses an alloca from the caller.
-      for (Value::use_iterator UI = TheAlloca->use_begin(),
-             E = TheAlloca->use_end(); UI != E; ++UI) {
-        CallInst *Call = dyn_cast<CallInst>(*UI);
+      for (User *U : TheAlloca->users()) {
+        CallInst *Call = dyn_cast<CallInst>(U);
         if (!Call)
           continue;
         Call->setTailCall(false);
@@ -836,7 +830,7 @@ CallGraphNode *ArgPromotion::DoPromotion(Function *F,
     ScalarizeTable &ArgIndices = ScalarizedElements[I];
 
     while (!I->use_empty()) {
-      if (LoadInst *LI = dyn_cast<LoadInst>(I->use_back())) {
+      if (LoadInst *LI = dyn_cast<LoadInst>(I->user_back())) {
         assert(ArgIndices.begin()->empty() &&
                "Load element should sort to front!");
         I2->setName(I->getName()+".val");
@@ -846,7 +840,7 @@ CallGraphNode *ArgPromotion::DoPromotion(Function *F,
         DEBUG(dbgs() << "*** Promoted load of argument '" << I->getName()
               << "' in function '" << F->getName() << "'\n");
       } else {
-        GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->use_back());
+        GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->user_back());
         IndicesVector Operands;
         Operands.reserve(GEP->getNumIndices());
         for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end();
@@ -876,7 +870,7 @@ CallGraphNode *ArgPromotion::DoPromotion(Function *F,
         // All of the uses must be load instructions.  Replace them all with
         // the argument specified by ArgNo.
         while (!GEP->use_empty()) {
-          LoadInst *L = cast<LoadInst>(GEP->use_back());
+          LoadInst *L = cast<LoadInst>(GEP->user_back());
           L->replaceAllUsesWith(TheArg);
           AA.replaceWithNewValue(L, TheArg);
           L->eraseFromParent();