[+0 self][pin removal] Teach pinremoval how to use RCIdentityAnalysis when removing pins.

Previously, we were being very conservative and were not trying to look through
any RCId uses. Now we understand how to look through RCIdentical instructions to
pair a pin and unpin. We also understand how to use the new getRCUses API on
RCIdentityAnalysis to get all uses of a value, looking through RCIdentical
instructions.

I also added some code to COWArrayOpts to teach it how to look through enum insts (which I needed).

Additionally I got stuck and added support for automatic indentation in Debug
statements. This is better than having to indent by hand every time.

There were no significant perf changes since this code was not being emitted by
the frontend. But without this +0 self causes COW to break.

rdar://20267677

Swift SVN r26529

lib/SILAnalysis/RCIdentityAnalysis.cpp

@@ -52,7 +52,7 @@ static bool isRCIdentityPreservingCast(ValueKind Kind) {
 }
 
 //===----------------------------------------------------------------------===//
-//                                  Analysis
+//                          RCIdentityRoot Analysis
 //===----------------------------------------------------------------------===//
 
 /// Returns true if FirstIV is a SILArgument or SILInstruction in a BB that
@@ -388,6 +388,56 @@ stripRCIdentityPreservingOps(SILValue V, unsigned RecursionDepth) {
   return V;
 }
 
+//===----------------------------------------------------------------------===//
+//                              RCUser Analysis
+//===----------------------------------------------------------------------===//
+
+/// Return all recursive users of V, looking through users which propagate
+/// RCIdentity.
+///
+/// We only use the instruction analysis here.
+void RCIdentityAnalysis::getRCUsers(
+    SILValue InputValue, llvm::SmallVectorImpl<SILInstruction *> &Users) {
+  // Add V to the worklist.
+  llvm::SmallVector<SILValue, 8> Worklist;
+  Worklist.push_back(InputValue);
+
+  // A set used to ensure we only visit users once.
+  llvm::SmallPtrSet<SILInstruction *, 8> VisitedInsts;
+
+  // Then until we finish the worklist...
+  while (!Worklist.empty()) {
+    // Pop off the top value.
+    SILValue V = Worklist.pop_back_val();
+
+    // For each user of V...
+    for (auto *Op : V.getUses()) {
+      SILInstruction *User = Op->getUser();
+
+      // If we have already visited this user, continue.
+      if (!VisitedInsts.insert(User).second)
+        continue;
+
+      // Otherwise attempt to strip off one layer of RC identical instructions
+      // from User.
+      SILValue StrippedRCID = stripRCIdentityPreservingInsts(User);
+
+      // If StrippedRCID is not V, then we know that User's result is
+      // conservatively not RCIdentical
+      // to V and we should add it to our RCUserList and continue.
+      if (StrippedRCID != V) {
+        Users.push_back(User);
+        continue;
+      }
+
+      // Otherwise, add all of User's uses to our list to continue searching.
+      for (unsigned i = 0, e = User->getNumTypes(); i != e; ++i) {
+        Worklist.push_back(SILValue(User, i));
+      }
+    }
+  }
+}
+
 //===----------------------------------------------------------------------===//
 //                              Main Entry Point
 //===----------------------------------------------------------------------===//