Initial checkin of InstVisitor class

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@1916 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Support/InstVisitor.h b/include/llvm/Support/InstVisitor.h
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+++ b/include/llvm/Support/InstVisitor.h
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+//===- llvm/Support/InstVisitor.h - Define instruction visitors --*- C++ -*--=//
+//
+// This template class is used to define instruction visitors in a typesafe
+// manner without having to use lots of casts and a big switch statement (in
+// your code that is).  The win here is that if instructions are added in the
+// future, they will be added to the InstVisitor<T> class, allowing you to
+// automatically support them (if you handle on of their superclasses).
+//
+// Note that this library is specifically designed as a template to avoid
+// virtual function call overhead.  Defining and using an InstVisitor is just as
+// efficient as having your own switch statement over the instruction opcode.
+//
+// InstVisitor Usage:
+//   You define InstVisitors from inheriting from the InstVisitor base class
+// and "overriding" functions in your class.  I say "overriding" because this
+// class is defined in terms of statically resolved overloading, not virtual
+// functions.  As an example, here is a visitor that counts the number of malloc
+// instructions processed:
+//
+//  // Declare the class.  Note that we derive from InstVisitor instantiated
+//  // with _our new subclasses_ type.
+//  //
+//  struct CountMallocVisitor : public InstVisitor<CountMallocVisitor> {
+//    unsigned Count;
+//    CountMallocVisitor() : Count(0) {}
+//
+//    void visitMallocInst(MallocInst *MI) { ++Count; }
+//  };
+//
+//  And this class would be used like this:
+//    CountMallocVistor CMV;
+//    CMV.visit(method);
+//    NumMallocs = CMV.Count;
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_INSTVISITOR_H
+#define LLVM_SUPPORT_INSTVISITOR_H
+
+#include "llvm/Instruction.h"
+
+// We operate on opaque instruction classes, so forward declare all instruction
+// types now...
+//
+#define HANDLE_INST(NUM, OPCODE, CLASS)   class CLASS;
+#include "llvm/Instruction.def"
+
+// Forward declare the intermediate types...
+class TerminatorInst; class UnaryOperator; class BinaryOperator;
+class AllocationInst; class MemAccessInst;
+
+template<typename SubClass>
+struct InstVisitor {
+  ~InstVisitor() {}           // We are meant to be derived from
+
+  //===--------------------------------------------------------------------===//
+  // Interface code - This is the public interface of the InstVisitor that you
+  // use to visit instructions...
+  //
+
+  // Generic visit method - Allow visitation to all instructions in a range
+  template<class Iterator>
+  void visit(Iterator Start, Iterator End) {
+    while (Start != End)
+      visit(*Start++);
+  }
+
+  // Define visitors for modules, methods and basic blocks...
+  //
+  void visit(Module *M) { visit(M->begin(), M->end()); }
+  void visit(Method *M) { visit(M->begin(), M->end()); }
+  void visit(BasicBlock *BB) { visit(BB->begin(), BB->end()); }
+
+  // visit - Finally, code to visit an instruction...
+  //
+  void visit(Instruction *I) {
+    switch (I->getOpcode()) {
+      // Build the switch statement using the Instruction.def file...
+#define HANDLE_INST(NUM, OPCODE, CLASS) \
+    case Instruction::OPCODE: ((SubClass*)this)->visit##CLASS((CLASS*)I); return;
+#include "llvm/Instruction.def"
+
+    default: assert(0 && "Unknown instruction type encountered!");
+    }
+  }
+
+  //===--------------------------------------------------------------------===//
+  // Visitation functions... these functions provide default fallbacks in case
+  // the user does not specify what to do for a particular instruction type.
+  // The default behavior is to generalize the instruction type to its subtype
+  // and try visiting the subtype.  All of this should be inlined perfectly,
+  // because there are no virtual functions to get in the way.
+  //
+  
+  // Specific Instruction type classes... note that all of the casts are
+  // neccesary because we use the instruction classes as opaque types...
+  //
+  void visitReturnInst(ReturnInst *I)               { ((SubClass*)this)->visitTerminatorInst((TerminatorInst*)I); }
+  void visitBranchInst(BranchInst *I)               { ((SubClass*)this)->visitTerminatorInst((TerminatorInst*)I); }
+  void visitSwitchInst(SwitchInst *I)               { ((SubClass*)this)->visitTerminatorInst((TerminatorInst*)I); }
+  void visitInvokeInst(InvokeInst *I)               { ((SubClass*)this)->visitTerminatorInst((TerminatorInst*)I); }
+  void visitGenericUnaryInst(GenericUnaryInst  *I)  { ((SubClass*)this)->visitUnaryOperator((UnaryOperator*)I); }
+  void visitGenericBinaryInst(GenericBinaryInst *I) { ((SubClass*)this)->visitBinaryOperator((BinaryOperator*)I); }
+  void visitSetCondInst(SetCondInst *I)             { ((SubClass*)this)->visitBinaryOperator((BinaryOperator *)I); }
+  void visitMallocInst(MallocInst *I)               { ((SubClass*)this)->visitAllocationInst((AllocationInst *)I); }
+  void visitAllocaInst(AllocaInst *I)               { ((SubClass*)this)->visitAllocationInst((AllocationInst *)I); }
+  void visitFreeInst(FreeInst   *I)                 { ((SubClass*)this)->visitInstruction((Instruction *)I); }
+  void visitLoadInst(LoadInst   *I)                 { ((SubClass*)this)->visitMemAccessInst((MemAccessInst *)I); }
+  void visitStoreInst(StoreInst  *I)                { ((SubClass*)this)->visitMemAccessInst((MemAccessInst *)I); }
+  void visitGetElementPtrInst(GetElementPtrInst *I) { ((SubClass*)this)->visitMemAccessInst((MemAccessInst *)I); }
+  void visitPHINode(PHINode    *I)                  { ((SubClass*)this)->visitInstruction((Instruction *)I); }
+  void visitCastInst(CastInst   *I)                 { ((SubClass*)this)->visitInstruction((Instruction *)I); }
+  void visitCallInst(CallInst   *I)                 { ((SubClass*)this)->visitInstruction((Instruction *)I); }
+  void visitShiftInst(ShiftInst  *I)                { ((SubClass*)this)->visitInstruction((Instruction *)I); }
+
+  // Next level propogators... if the user does not overload a specific
+  // instruction type, they can overload one of these to get the whole class
+  // of instructions...
+  //
+  void visitTerminatorInst(TerminatorInst *I) { ((SubClass*)this)->visitInstruction((Instruction*)I); }
+  void visitUnaryOperator (UnaryOperator  *I) { ((SubClass*)this)->visitInstruction((Instruction*)I); }
+  void visitBinaryOperator(BinaryOperator *I) { ((SubClass*)this)->visitInstruction((Instruction*)I); }
+  void visitAllocationInst(AllocationInst *I) { ((SubClass*)this)->visitInstruction((Instruction*)I); }
+  void visitMemAccessInst (MemAccessInst  *I) { ((SubClass*)this)->visitInstruction((Instruction*)I); }
+
+  // If the user wants a 'default' case, they can choose to override this
+  // function.  If this function is not overloaded in the users subclass, then
+  // this instruction just gets ignored.
+  //
+  void visitInstruction(Instruction *I) {}  // Ignore unhandled instructions
+};
+
+#endif