Move the special Phi logic for hung off uses in to User::allocHungOffUses. NFC.

PhiNode's need to allocate space for an array of Use[N] and then BasicBlock*[N].

They had their own allocHungOffUses to handle all of this.  This moves the logic
in to User::allocHungOffUses and PhiNode passes in a bool to say to allocate
the BB* space too.

Reviewed by Duncan Exon Smith.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239489 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/IR/Instructions.h

@@ -2248,7 +2248,9 @@ protected:
   // allocHungoffUses - this is more complicated than the generic
   // User::allocHungoffUses, because we have to allocate Uses for the incoming
   // values and pointers to the incoming blocks, all in one allocation.
-  Use *allocHungoffUses(unsigned) const;
+  Use *allocHungoffUses(unsigned N) const {
+    return User::allocHungoffUses(N, /* IsPhi */ true);
+  }
 
   PHINode *clone_impl() const override;
 public:

include/llvm/IR/User.h

@@ -52,7 +52,12 @@ protected:
       : Value(ty, vty), OperandList(OpList) {
     NumOperands = NumOps;
   }
-  Use *allocHungoffUses(unsigned) const;
+
+  /// \brief Allocate the array of Uses, followed by a pointer
+  /// (with bottom bit set) to the User.
+  /// \param IsPhi identifies callers which are phi nodes and which need
+  /// N BasicBlock* allocated along with N
+  Use *allocHungoffUses(unsigned N, bool IsPhi = false) const;
   void dropHungoffUses() {
     Use::zap(OperandList, OperandList + NumOperands, true);
     OperandList = nullptr;

lib/IR/Instructions.cpp

@@ -97,18 +97,6 @@ PHINode::~PHINode() {
   dropHungoffUses();
 }
 
-Use *PHINode::allocHungoffUses(unsigned N) const {
-  // Allocate the array of Uses of the incoming values, followed by a pointer
-  // (with bottom bit set) to the User, followed by the array of pointers to
-  // the incoming basic blocks.
-  size_t size = N * sizeof(Use) + sizeof(Use::UserRef)
-    + N * sizeof(BasicBlock*);
-  Use *Begin = static_cast<Use*>(::operator new(size));
-  Use *End = Begin + N;
-  (void) new(End) Use::UserRef(const_cast<PHINode*>(this), 1);
-  return Use::initTags(Begin, End);
-}
-
 // removeIncomingValue - Remove an incoming value.  This is useful if a
 // predecessor basic block is deleted.
 Value *PHINode::removeIncomingValue(unsigned Idx, bool DeletePHIIfEmpty) {

lib/IR/User.cpp

@@ -13,6 +13,7 @@
 #include "llvm/IR/Operator.h"
 
 namespace llvm {
+class BasicBlock;
 
 //===----------------------------------------------------------------------===//
 //                                 User Class
@@ -39,10 +40,12 @@ void User::replaceUsesOfWith(Value *From, Value *To) {
 //                         User allocHungoffUses Implementation
 //===----------------------------------------------------------------------===//
 
-Use *User::allocHungoffUses(unsigned N) const {
+Use *User::allocHungoffUses(unsigned N, bool IsPhi) const {
   // Allocate the array of Uses, followed by a pointer (with bottom bit set) to
   // the User.
   size_t size = N * sizeof(Use) + sizeof(Use::UserRef);
+  if (IsPhi)
+    size += N * sizeof(BasicBlock *);
   Use *Begin = static_cast<Use*>(::operator new(size));
   Use *End = Begin + N;
   (void) new(End) Use::UserRef(const_cast<User*>(this), 1);