Instructions: add missing anchors. NFC

[thegameg]

Summary

ICmpInst, GetElementPtrInst and PHINode have no anchor functions. This causes the vtable and the type info (if RTTI is enabled in user code) to be emitted in multiple translation units.

Before 3.7, the destructors were the key functions for these nodes, but they have been removed.

There have been discussions about this here: http://lists.llvm.org/pipermail/llvm-dev/2015-August/089010.html and here: http://lists.llvm.org/pipermail/llvm-dev/2015-December/092921.html.

[thegameg]

Also, it looks like the LLVM Coding Standards recommends it as well: http://llvm.org/docs/CodingStandards.html#provide-a-virtual-method-anchor-for-classes-in-headers

[pete]

Thanks for doing this. Makes sense as per the coding guidelines.

LGTM.

[thegameg]

Thanks for the review. I don't have commit rights, can you commit this for me?

[pete]

Sure. Committed it as r255538.

Thanks again for the fix
Pete

[thegameg]

Thank you!

include/llvm/IR/Instructions.h

   Type *SourceElementType;
   Type *ResultElementType;
 
+  void anchor() override;
+
   GetElementPtrInst(const GetElementPtrInst &GEPI);
   void init(Value *Ptr, ArrayRef<Value *> IdxList, const Twine &NameStr);
 

 /// must be identical types.
 /// \brief Represent an integer comparison operator.
 class ICmpInst: public CmpInst {
+  void anchor() override;
+
   void AssertOK() {
     assert(getPredicate() >= CmpInst::FIRST_ICMP_PREDICATE &&
            getPredicate() <= CmpInst::LAST_ICMP_PREDICATE &&

 // scientist's overactive imagination.
 //
 class PHINode : public Instruction {
+  void anchor() override;
+
   void *operator new(size_t, unsigned) = delete;
   /// ReservedSpace - The number of operands actually allocated.  NumOperands is
   /// the number actually in use.

lib/IR/Instructions.cpp

 //                               PHINode Class
 //===----------------------------------------------------------------------===//
 
+void PHINode::anchor() {}
+
 PHINode::PHINode(const PHINode &PN)
     : Instruction(PN.getType(), Instruction::PHI, nullptr, PN.getNumOperands()),
       ReservedSpace(PN.getNumOperands()) {

 //                       GetElementPtrInst Implementation
 //===----------------------------------------------------------------------===//
 
+void GetElementPtrInst::anchor() {}
+
 void GetElementPtrInst::init(Value *Ptr, ArrayRef<Value *> IdxList,
                              const Twine &Name) {
   assert(getNumOperands() == 1 + IdxList.size() &&

   }
 }
 
+void ICmpInst::anchor() {}
+
 ICmpInst::Predicate ICmpInst::getSignedPredicate(Predicate pred) {
   switch (pred) {
     default: llvm_unreachable("Unknown icmp predicate!");