[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

2 files changed, 15 insertions, 17 deletions

diff --git a/lib/Analysis/IPA/GlobalsModRef.cpp b/lib/Analysis/IPA/GlobalsModRef.cpp
index dac9bd24a4..f4097e4631 100644
--- a/lib/Analysis/IPA/GlobalsModRef.cpp
+++ b/lib/Analysis/IPA/GlobalsModRef.cpp
@@ -252,33 +252,33 @@ bool GlobalsModRef::AnalyzeUsesOfPointer(Value *V,
                                          GlobalValue *OkayStoreDest) {
   if (!V->getType()->isPointerTy()) return true;
 
-  for (Value::use_iterator UI = V->use_begin(), E=V->use_end(); UI != E; ++UI) {
-    User *U = *UI;
-    if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
+  for (Use &U : V->uses()) {
+    User *I = U.getUser();
+    if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
       Readers.push_back(LI->getParent()->getParent());
-    } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
+    } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
       if (V == SI->getOperand(1)) {
         Writers.push_back(SI->getParent()->getParent());
       } else if (SI->getOperand(1) != OkayStoreDest) {
         return true;  // Storing the pointer
       }
-    } else if (Operator::getOpcode(U) == Instruction::GetElementPtr) {
-      if (AnalyzeUsesOfPointer(U, Readers, Writers))
+    } else if (Operator::getOpcode(I) == Instruction::GetElementPtr) {
+      if (AnalyzeUsesOfPointer(I, Readers, Writers))
         return true;
-    } else if (Operator::getOpcode(U) == Instruction::BitCast) {
-      if (AnalyzeUsesOfPointer(U, Readers, Writers, OkayStoreDest))
+    } else if (Operator::getOpcode(I) == Instruction::BitCast) {
+      if (AnalyzeUsesOfPointer(I, Readers, Writers, OkayStoreDest))
         return true;
-    } else if (CallSite CS = U) {
+    } else if (CallSite CS = I) {
       // Make sure that this is just the function being called, not that it is
       // passing into the function.
-      if (!CS.isCallee(UI)) {
+      if (!CS.isCallee(&U)) {
         // Detect calls to free.
-        if (isFreeCall(U, TLI))
+        if (isFreeCall(I, TLI))
           Writers.push_back(CS->getParent()->getParent());
         else
           return true; // Argument of an unknown call.
       }
-    } else if (ICmpInst *ICI = dyn_cast<ICmpInst>(U)) {
+    } else if (ICmpInst *ICI = dyn_cast<ICmpInst>(I)) {
       if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
         return true;  // Allow comparison against null.
     } else {
@@ -303,8 +303,7 @@ bool GlobalsModRef::AnalyzeIndirectGlobalMemory(GlobalValue *GV) {
 
   // Walk the user list of the global.  If we find anything other than a direct
   // load or store, bail out.
-  for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I){
-    User *U = *I;
+  for (User *U : GV->users()) {
     if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
       // The pointer loaded from the global can only be used in simple ways:
       // we allow addressing of it and loading storing to it.  We do *not* allow
diff --git a/lib/Analysis/IPA/InlineCost.cpp b/lib/Analysis/IPA/InlineCost.cpp
index 62c717859c..d4ef2247e2 100644
--- a/lib/Analysis/IPA/InlineCost.cpp
+++ b/lib/Analysis/IPA/InlineCost.cpp
@@ -1052,9 +1052,8 @@ bool CallAnalyzer::analyzeCall(CallSite CS) {
 
   Function *Caller = CS.getInstruction()->getParent()->getParent();
   // Check if the caller function is recursive itself.
-  for (Value::use_iterator U = Caller->use_begin(), E = Caller->use_end();
-       U != E; ++U) {
-    CallSite Site(cast<Value>(*U));
+  for (User *U : Caller->users()) {
+    CallSite Site(U);
     if (!Site)
       continue;
     Instruction *I = Site.getInstruction();