[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, 36 insertions, 33 deletions

diff --git a/llvm/lib/Transforms/Vectorize/BBVectorize.cpp b/llvm/lib/Transforms/Vectorize/BBVectorize.cpp
index c90cc8fb479..71350e7b39c 100644
--- a/llvm/lib/Transforms/Vectorize/BBVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/BBVectorize.cpp
@@ -1318,13 +1318,15 @@ namespace {
 
     // For each possible pairing for this variable, look at the uses of
     // the first value...
-    for (Value::use_iterator I = P.first->use_begin(),
-         E = P.first->use_end(); I != E; ++I) {
-      if (isa<LoadInst>(*I)) {
+    for (Value::user_iterator I = P.first->user_begin(),
+                              E = P.first->user_end();
+         I != E; ++I) {
+      User *UI = *I;
+      if (isa<LoadInst>(UI)) {
         // A pair cannot be connected to a load because the load only takes one
         // operand (the address) and it is a scalar even after vectorization.
         continue;
-      } else if ((SI = dyn_cast<StoreInst>(*I)) &&
+      } else if ((SI = dyn_cast<StoreInst>(UI)) &&
                  P.first == SI->getPointerOperand()) {
         // Similarly, a pair cannot be connected to a store through its
         // pointer operand.
@@ -1333,22 +1335,21 @@ namespace {
 
       // For each use of the first variable, look for uses of the second
       // variable...
-      for (Value::use_iterator J = P.second->use_begin(),
-           E2 = P.second->use_end(); J != E2; ++J) {
-        if ((SJ = dyn_cast<StoreInst>(*J)) &&
+      for (User *UJ : P.second->users()) {
+        if ((SJ = dyn_cast<StoreInst>(UJ)) &&
             P.second == SJ->getPointerOperand())
           continue;
 
         // Look for <I, J>:
-        if (CandidatePairsSet.count(ValuePair(*I, *J))) {
-          VPPair VP(P, ValuePair(*I, *J));
+        if (CandidatePairsSet.count(ValuePair(UI, UJ))) {
+          VPPair VP(P, ValuePair(UI, UJ));
           ConnectedPairs[VP.first].push_back(VP.second);
           PairConnectionTypes.insert(VPPairWithType(VP, PairConnectionDirect));
         }
 
         // Look for <J, I>:
-        if (CandidatePairsSet.count(ValuePair(*J, *I))) {
-          VPPair VP(P, ValuePair(*J, *I));
+        if (CandidatePairsSet.count(ValuePair(UJ, UI))) {
+          VPPair VP(P, ValuePair(UJ, UI));
           ConnectedPairs[VP.first].push_back(VP.second);
           PairConnectionTypes.insert(VPPairWithType(VP, PairConnectionSwap));
         }
@@ -1357,13 +1358,14 @@ namespace {
       if (Config.SplatBreaksChain) continue;
       // Look for cases where just the first value in the pair is used by
       // both members of another pair (splatting).
-      for (Value::use_iterator J = P.first->use_begin(); J != E; ++J) {
-        if ((SJ = dyn_cast<StoreInst>(*J)) &&
+      for (Value::user_iterator J = P.first->user_begin(); J != E; ++J) {
+        User *UJ = *J;
+        if ((SJ = dyn_cast<StoreInst>(UJ)) &&
             P.first == SJ->getPointerOperand())
           continue;
 
-        if (CandidatePairsSet.count(ValuePair(*I, *J))) {
-          VPPair VP(P, ValuePair(*I, *J));
+        if (CandidatePairsSet.count(ValuePair(UI, UJ))) {
+          VPPair VP(P, ValuePair(UI, UJ));
           ConnectedPairs[VP.first].push_back(VP.second);
           PairConnectionTypes.insert(VPPairWithType(VP, PairConnectionSplat));
         }
@@ -1373,21 +1375,24 @@ namespace {
     if (Config.SplatBreaksChain) return;
     // Look for cases where just the second value in the pair is used by
     // both members of another pair (splatting).
-    for (Value::use_iterator I = P.second->use_begin(),
-         E = P.second->use_end(); I != E; ++I) {
-      if (isa<LoadInst>(*I))
+    for (Value::user_iterator I = P.second->user_begin(),
+                              E = P.second->user_end();
+         I != E; ++I) {
+      User *UI = *I;
+      if (isa<LoadInst>(UI))
         continue;
-      else if ((SI = dyn_cast<StoreInst>(*I)) &&
+      else if ((SI = dyn_cast<StoreInst>(UI)) &&
                P.second == SI->getPointerOperand())
         continue;
 
-      for (Value::use_iterator J = P.second->use_begin(); J != E; ++J) {
-        if ((SJ = dyn_cast<StoreInst>(*J)) &&
+      for (Value::user_iterator J = P.second->user_begin(); J != E; ++J) {
+        User *UJ = *J;
+        if ((SJ = dyn_cast<StoreInst>(UJ)) &&
             P.second == SJ->getPointerOperand())
           continue;
 
-        if (CandidatePairsSet.count(ValuePair(*I, *J))) {
-          VPPair VP(P, ValuePair(*I, *J));
+        if (CandidatePairsSet.count(ValuePair(UI, UJ))) {
+          VPPair VP(P, ValuePair(UI, UJ));
           ConnectedPairs[VP.first].push_back(VP.second);
           PairConnectionTypes.insert(VPPairWithType(VP, PairConnectionSplat));
         }
@@ -1947,16 +1952,15 @@ namespace {
             Type *VTy = getVecTypeForPair(Ty1, Ty2);
 
             bool NeedsExtraction = false;
-            for (Value::use_iterator I = S->first->use_begin(),
-                 IE = S->first->use_end(); I != IE; ++I) {
-              if (ShuffleVectorInst *SI = dyn_cast<ShuffleVectorInst>(*I)) {
+            for (User *U : S->first->users()) {
+              if (ShuffleVectorInst *SI = dyn_cast<ShuffleVectorInst>(U)) {
                 // Shuffle can be folded if it has no other input
                 if (isa<UndefValue>(SI->getOperand(1)))
                   continue;
               }
-              if (isa<ExtractElementInst>(*I))
+              if (isa<ExtractElementInst>(U))
                 continue;
-              if (PrunedDAGInstrs.count(*I))
+              if (PrunedDAGInstrs.count(U))
                 continue;
               NeedsExtraction = true;
               break;
@@ -1979,16 +1983,15 @@ namespace {
             }
 
             NeedsExtraction = false;
-            for (Value::use_iterator I = S->second->use_begin(),
-                 IE = S->second->use_end(); I != IE; ++I) {
-              if (ShuffleVectorInst *SI = dyn_cast<ShuffleVectorInst>(*I)) {
+            for (User *U : S->second->users()) {
+              if (ShuffleVectorInst *SI = dyn_cast<ShuffleVectorInst>(U)) {
                 // Shuffle can be folded if it has no other input
                 if (isa<UndefValue>(SI->getOperand(1)))
                   continue;
               }
-              if (isa<ExtractElementInst>(*I))
+              if (isa<ExtractElementInst>(U))
                 continue;
-              if (PrunedDAGInstrs.count(*I))
+              if (PrunedDAGInstrs.count(U))
                 continue;
               NeedsExtraction = true;
               break;