[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

1 files changed, 8 insertions, 10 deletions

diff --git a/lib/Transforms/Utils/GlobalStatus.cpp b/lib/Transforms/Utils/GlobalStatus.cpp
index 17d6258cf0..e9ebc452a0 100644
--- a/lib/Transforms/Utils/GlobalStatus.cpp
+++ b/lib/Transforms/Utils/GlobalStatus.cpp
@@ -35,9 +35,8 @@ bool llvm::isSafeToDestroyConstant(const Constant *C) {
   if (isa<GlobalValue>(C))
     return false;
 
-  for (Value::const_use_iterator UI = C->use_begin(), E = C->use_end(); UI != E;
-       ++UI)
-    if (const Constant *CU = dyn_cast<Constant>(*UI)) {
+  for (const User *U : C->users())
+    if (const Constant *CU = dyn_cast<Constant>(U)) {
       if (!isSafeToDestroyConstant(CU))
         return false;
     } else
@@ -47,10 +46,9 @@ bool llvm::isSafeToDestroyConstant(const Constant *C) {
 
 static bool analyzeGlobalAux(const Value *V, GlobalStatus &GS,
                              SmallPtrSet<const PHINode *, 16> &PhiUsers) {
-  for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
-       ++UI) {
-    const User *U = *UI;
-    if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
+  for (const Use &U : V->uses()) {
+    const User *UR = U.getUser();
+    if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(UR)) {
       GS.HasNonInstructionUser = true;
 
       // If the result of the constantexpr isn't pointer type, then we won't
@@ -60,7 +58,7 @@ static bool analyzeGlobalAux(const Value *V, GlobalStatus &GS,
 
       if (analyzeGlobalAux(CE, GS, PhiUsers))
         return true;
-    } else if (const Instruction *I = dyn_cast<Instruction>(U)) {
+    } else if (const Instruction *I = dyn_cast<Instruction>(UR)) {
       if (!GS.HasMultipleAccessingFunctions) {
         const Function *F = I->getParent()->getParent();
         if (GS.AccessingFunction == 0)
@@ -150,13 +148,13 @@ static bool analyzeGlobalAux(const Value *V, GlobalStatus &GS,
           return true;
         GS.StoredType = GlobalStatus::Stored;
       } else if (ImmutableCallSite C = I) {
-        if (!C.isCallee(UI))
+        if (!C.isCallee(&U))
           return true;
         GS.IsLoaded = true;
       } else {
         return true; // Any other non-load instruction might take address!
       }
-    } else if (const Constant *C = dyn_cast<Constant>(U)) {
+    } else if (const Constant *C = dyn_cast<Constant>(UR)) {
       GS.HasNonInstructionUser = true;
       // We might have a dead and dangling constant hanging off of here.
       if (!isSafeToDestroyConstant(C))