[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, 23 insertions, 29 deletions

diff --git a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
index 12614d5..7537632 100644
--- a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -269,11 +269,11 @@ void IndVarSimplify::HandleFloatingPointIV(Loop *L, PHINode *PN) {
 
   // Check Incr uses. One user is PN and the other user is an exit condition
   // used by the conditional terminator.
-  Value::use_iterator IncrUse = Incr->use_begin();
+  Value::user_iterator IncrUse = Incr->user_begin();
   Instruction *U1 = cast<Instruction>(*IncrUse++);
-  if (IncrUse == Incr->use_end()) return;
+  if (IncrUse == Incr->user_end()) return;
   Instruction *U2 = cast<Instruction>(*IncrUse++);
-  if (IncrUse != Incr->use_end()) return;
+  if (IncrUse != Incr->user_end()) return;
 
   // Find exit condition, which is an fcmp.  If it doesn't exist, or if it isn't
   // only used by a branch, we can't transform it.
@@ -281,10 +281,10 @@ void IndVarSimplify::HandleFloatingPointIV(Loop *L, PHINode *PN) {
   if (!Compare)
     Compare = dyn_cast<FCmpInst>(U2);
   if (Compare == 0 || !Compare->hasOneUse() ||
-      !isa<BranchInst>(Compare->use_back()))
+      !isa<BranchInst>(Compare->user_back()))
     return;
 
-  BranchInst *TheBr = cast<BranchInst>(Compare->use_back());
+  BranchInst *TheBr = cast<BranchInst>(Compare->user_back());
 
   // We need to verify that the branch actually controls the iteration count
   // of the loop.  If not, the new IV can overflow and no one will notice.
@@ -563,8 +563,8 @@ void IndVarSimplify::RewriteLoopExitValues(Loop *L, SCEVExpander &Rewriter) {
           unsigned NumHardInternalUses = 0;
           unsigned NumSoftExternalUses = 0;
           unsigned NumUses = 0;
-          for (Value::use_iterator IB=Inst->use_begin(), IE=Inst->use_end();
-               IB!=IE && NumUses<=6 ; ++IB) {
+          for (auto IB = Inst->user_begin(), IE = Inst->user_end();
+               IB != IE && NumUses <= 6; ++IB) {
             Instruction *UseInstr = cast<Instruction>(*IB);
             unsigned Opc = UseInstr->getOpcode();
             NumUses++;
@@ -576,9 +576,9 @@ void IndVarSimplify::RewriteLoopExitValues(Loop *L, SCEVExpander &Rewriter) {
                 // Do not count the Phi as a use. LCSSA may have inserted
                 // plenty of trivial ones.
                 NumUses--;
-                for (Value::use_iterator PB=UseInstr->use_begin(),
-                                         PE=UseInstr->use_end();
-                     PB!=PE && NumUses<=6 ; ++PB, ++NumUses) {
+                for (auto PB = UseInstr->user_begin(),
+                          PE = UseInstr->user_end();
+                     PB != PE && NumUses <= 6; ++PB, ++NumUses) {
                   unsigned PhiOpc = cast<Instruction>(*PB)->getOpcode();
                   if (PhiOpc != Instruction::Call && PhiOpc != Instruction::Ret)
                     NumSoftExternalUses++;
@@ -1018,15 +1018,14 @@ Instruction *WidenIV::WidenIVUse(NarrowIVDefUse DU, SCEVExpander &Rewriter) {
 /// pushNarrowIVUsers - Add eligible users of NarrowDef to NarrowIVUsers.
 ///
 void WidenIV::pushNarrowIVUsers(Instruction *NarrowDef, Instruction *WideDef) {
-  for (Value::use_iterator UI = NarrowDef->use_begin(),
-         UE = NarrowDef->use_end(); UI != UE; ++UI) {
-    Instruction *NarrowUse = cast<Instruction>(*UI);
+  for (User *U : NarrowDef->users()) {
+    Instruction *NarrowUser = cast<Instruction>(U);
 
     // Handle data flow merges and bizarre phi cycles.
-    if (!Widened.insert(NarrowUse))
+    if (!Widened.insert(NarrowUser))
       continue;
 
-    NarrowIVUsers.push_back(NarrowIVDefUse(NarrowDef, NarrowUse, WideDef));
+    NarrowIVUsers.push_back(NarrowIVDefUse(NarrowDef, NarrowUser, WideDef));
   }
 }
 
@@ -1417,15 +1416,11 @@ static bool AlmostDeadIV(PHINode *Phi, BasicBlock *LatchBlock, Value *Cond) {
   int LatchIdx = Phi->getBasicBlockIndex(LatchBlock);
   Value *IncV = Phi->getIncomingValue(LatchIdx);
 
-  for (Value::use_iterator UI = Phi->use_begin(), UE = Phi->use_end();
-       UI != UE; ++UI) {
-    if (*UI != Cond && *UI != IncV) return false;
-  }
+  for (User *U : Phi->users())
+    if (U != Cond && U != IncV) return false;
 
-  for (Value::use_iterator UI = IncV->use_begin(), UE = IncV->use_end();
-       UI != UE; ++UI) {
-    if (*UI != Cond && *UI != Phi) return false;
-  }
+  for (User *U : IncV->users())
+    if (U != Cond && U != Phi) return false;
   return true;
 }
 
@@ -1755,13 +1750,12 @@ void IndVarSimplify::SinkUnusedInvariants(Loop *L) {
     // Determine if there is a use in or before the loop (direct or
     // otherwise).
     bool UsedInLoop = false;
-    for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
-         UI != UE; ++UI) {
-      User *U = *UI;
-      BasicBlock *UseBB = cast<Instruction>(U)->getParent();
-      if (PHINode *P = dyn_cast<PHINode>(U)) {
+    for (Use &U : I->uses()) {
+      Instruction *User = cast<Instruction>(U.getUser());
+      BasicBlock *UseBB = User->getParent();
+      if (PHINode *P = dyn_cast<PHINode>(User)) {
         unsigned i =
-          PHINode::getIncomingValueNumForOperand(UI.getOperandNo());
+          PHINode::getIncomingValueNumForOperand(U.getOperandNo());
         UseBB = P->getIncomingBlock(i);
       }
       if (UseBB == Preheader || L->contains(UseBB)) {