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//===- InstVisitor.h - Instruction visitor templates ------------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "llvm/IR/CallSite.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/ErrorHandling.h"
namespace llvm {
// We operate on opaque instruction classes, so forward declare all instruction
// types now...
#include "llvm/IR/Instruction.def"
return static_cast<SubClass*>(this)-> \
/// Base class for instruction visitors
/// Instruction visitors are used when you want to perform different actions
/// for different kinds of instructions without having to use lots of casts
/// and a big switch statement (in your code, that is).
/// To define your own visitor, inherit from this class, specifying your
/// new type for the 'SubClass' template parameter, and "override" visitXXX
/// functions in your class. I say "override" because this class is defined
/// in terms of statically resolved overloading, not virtual functions.
/// For 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 CountAllocaVisitor : public InstVisitor<CountAllocaVisitor> {
/// unsigned Count;
/// CountAllocaVisitor() : Count(0) {}
/// void visitAllocaInst(AllocaInst &AI) { ++Count; }
/// };
/// And this class would be used like this:
/// CountAllocaVisitor CAV;
/// CAV.visit(function);
/// NumAllocas = CAV.Count;
/// The defined has 'visit' methods for Instruction, and also for BasicBlock,
/// Function, and Module, which recursively process all contained instructions.
/// Note that if you don't implement visitXXX for some instruction type,
/// the visitXXX method for instruction superclass will be invoked. So
/// if instructions are added in the future, they will be automatically
/// supported, if you handle one of their superclasses.
/// The optional second template argument specifies the type that instruction
/// visitation functions should return. If you specify this, you *MUST* provide
/// an implementation of visitInstruction though!.
/// Note that this class 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.
template<typename SubClass, typename RetTy=void>
class InstVisitor {
// 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)
// Define visitors for functions and basic blocks...
void visit(Module &M) {
visit(M.begin(), M.end());
void visit(Function &F) {
visit(F.begin(), F.end());
void visit(BasicBlock &BB) {
visit(BB.begin(), BB.end());
// Forwarding functions so that the user can visit with pointers AND refs.
void visit(Module *M) { visit(*M); }
void visit(Function *F) { visit(*F); }
void visit(BasicBlock *BB) { visit(*BB); }
RetTy visit(Instruction *I) { return visit(*I); }
// visit - Finally, code to visit an instruction...
RetTy visit(Instruction &I) {
static_assert(std::is_base_of<InstVisitor, SubClass>::value,
"Must pass the derived type to this template!");
switch (I.getOpcode()) {
default: llvm_unreachable("Unknown instruction type encountered!");
// Build the switch statement using the Instruction.def file...
case Instruction::OPCODE: return \
static_cast<SubClass*>(this)-> \
#include "llvm/IR/Instruction.def"
// 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.
// When visiting a module, function or basic block directly, these methods get
// called to indicate when transitioning into a new unit.
void visitModule (Module &M) {}
void visitFunction (Function &F) {}
void visitBasicBlock(BasicBlock &BB) {}
// Define instruction specific visitor functions that can be overridden to
// handle SPECIFIC instructions. These functions automatically define
// visitMul to proxy to visitBinaryOperator for instance in case the user does
// not need this generality.
// These functions can also implement fan-out, when a single opcode and
// instruction have multiple more specific Instruction subclasses. The Call
// instruction currently supports this. We implement that by redirecting that
// instruction to a special delegation helper.
RetTy visit##OPCODE(CLASS &I) { \
if (NUM == Instruction::Call) \
return delegateCallInst(I); \
else \
#include "llvm/IR/Instruction.def"
// Specific Instruction type classes... note that all of the casts are
// necessary because we use the instruction classes as opaque types...
RetTy visitICmpInst(ICmpInst &I) { DELEGATE(CmpInst);}
RetTy visitFCmpInst(FCmpInst &I) { DELEGATE(CmpInst);}
RetTy visitAllocaInst(AllocaInst &I) { DELEGATE(UnaryInstruction);}
RetTy visitLoadInst(LoadInst &I) { DELEGATE(UnaryInstruction);}
RetTy visitStoreInst(StoreInst &I) { DELEGATE(Instruction);}
RetTy visitAtomicCmpXchgInst(AtomicCmpXchgInst &I) { DELEGATE(Instruction);}
RetTy visitAtomicRMWInst(AtomicRMWInst &I) { DELEGATE(Instruction);}
RetTy visitFenceInst(FenceInst &I) { DELEGATE(Instruction);}
RetTy visitGetElementPtrInst(GetElementPtrInst &I){ DELEGATE(Instruction);}
RetTy visitPHINode(PHINode &I) { DELEGATE(Instruction);}
RetTy visitTruncInst(TruncInst &I) { DELEGATE(CastInst);}
RetTy visitZExtInst(ZExtInst &I) { DELEGATE(CastInst);}
RetTy visitSExtInst(SExtInst &I) { DELEGATE(CastInst);}
RetTy visitFPTruncInst(FPTruncInst &I) { DELEGATE(CastInst);}
RetTy visitFPExtInst(FPExtInst &I) { DELEGATE(CastInst);}
RetTy visitFPToUIInst(FPToUIInst &I) { DELEGATE(CastInst);}
RetTy visitFPToSIInst(FPToSIInst &I) { DELEGATE(CastInst);}
RetTy visitUIToFPInst(UIToFPInst &I) { DELEGATE(CastInst);}
RetTy visitSIToFPInst(SIToFPInst &I) { DELEGATE(CastInst);}
RetTy visitPtrToIntInst(PtrToIntInst &I) { DELEGATE(CastInst);}
RetTy visitIntToPtrInst(IntToPtrInst &I) { DELEGATE(CastInst);}
RetTy visitBitCastInst(BitCastInst &I) { DELEGATE(CastInst);}
RetTy visitAddrSpaceCastInst(AddrSpaceCastInst &I) { DELEGATE(CastInst);}
RetTy visitSelectInst(SelectInst &I) { DELEGATE(Instruction);}
RetTy visitVAArgInst(VAArgInst &I) { DELEGATE(UnaryInstruction);}
RetTy visitExtractElementInst(ExtractElementInst &I) { DELEGATE(Instruction);}
RetTy visitInsertElementInst(InsertElementInst &I) { DELEGATE(Instruction);}
RetTy visitShuffleVectorInst(ShuffleVectorInst &I) { DELEGATE(Instruction);}
RetTy visitExtractValueInst(ExtractValueInst &I){ DELEGATE(UnaryInstruction);}
RetTy visitInsertValueInst(InsertValueInst &I) { DELEGATE(Instruction); }
RetTy visitLandingPadInst(LandingPadInst &I) { DELEGATE(Instruction); }
RetTy visitFuncletPadInst(FuncletPadInst &I) { DELEGATE(Instruction); }
RetTy visitCleanupPadInst(CleanupPadInst &I) { DELEGATE(FuncletPadInst); }
RetTy visitCatchPadInst(CatchPadInst &I) { DELEGATE(FuncletPadInst); }
// Handle the special instrinsic instruction classes.
RetTy visitDbgDeclareInst(DbgDeclareInst &I) { DELEGATE(DbgVariableIntrinsic);}
RetTy visitDbgValueInst(DbgValueInst &I) { DELEGATE(DbgVariableIntrinsic);}
RetTy visitDbgVariableIntrinsic(DbgVariableIntrinsic &I)
{ DELEGATE(DbgInfoIntrinsic);}
RetTy visitDbgLabelInst(DbgLabelInst &I) { DELEGATE(DbgInfoIntrinsic);}
RetTy visitDbgInfoIntrinsic(DbgInfoIntrinsic &I){ DELEGATE(IntrinsicInst); }
RetTy visitMemSetInst(MemSetInst &I) { DELEGATE(MemIntrinsic); }
RetTy visitMemCpyInst(MemCpyInst &I) { DELEGATE(MemTransferInst); }
RetTy visitMemMoveInst(MemMoveInst &I) { DELEGATE(MemTransferInst); }
RetTy visitMemTransferInst(MemTransferInst &I) { DELEGATE(MemIntrinsic); }
RetTy visitMemIntrinsic(MemIntrinsic &I) { DELEGATE(IntrinsicInst); }
RetTy visitVAStartInst(VAStartInst &I) { DELEGATE(IntrinsicInst); }
RetTy visitVAEndInst(VAEndInst &I) { DELEGATE(IntrinsicInst); }
RetTy visitVACopyInst(VACopyInst &I) { DELEGATE(IntrinsicInst); }
RetTy visitIntrinsicInst(IntrinsicInst &I) { DELEGATE(CallInst); }
// Call, Invoke and CallBr are slightly different as they delegate first
// through a generic CallSite visitor.
RetTy visitCallInst(CallInst &I) {
return static_cast<SubClass*>(this)->visitCallSite(&I);
RetTy visitInvokeInst(InvokeInst &I) {
return static_cast<SubClass*>(this)->visitCallSite(&I);
RetTy visitCallBrInst(CallBrInst &I) {
return static_cast<SubClass *>(this)->visitCallSite(&I);
// While terminators don't have a distinct type modeling them, we support
// intercepting them with dedicated a visitor callback.
RetTy visitReturnInst(ReturnInst &I) {
return static_cast<SubClass *>(this)->visitTerminator(I);
RetTy visitBranchInst(BranchInst &I) {
return static_cast<SubClass *>(this)->visitTerminator(I);
RetTy visitSwitchInst(SwitchInst &I) {
return static_cast<SubClass *>(this)->visitTerminator(I);
RetTy visitIndirectBrInst(IndirectBrInst &I) {
return static_cast<SubClass *>(this)->visitTerminator(I);
RetTy visitResumeInst(ResumeInst &I) {
return static_cast<SubClass *>(this)->visitTerminator(I);
RetTy visitUnreachableInst(UnreachableInst &I) {
return static_cast<SubClass *>(this)->visitTerminator(I);
RetTy visitCleanupReturnInst(CleanupReturnInst &I) {
return static_cast<SubClass *>(this)->visitTerminator(I);
RetTy visitCatchReturnInst(CatchReturnInst &I) {
return static_cast<SubClass *>(this)->visitTerminator(I);
RetTy visitCatchSwitchInst(CatchSwitchInst &I) {
return static_cast<SubClass *>(this)->visitTerminator(I);
RetTy visitTerminator(Instruction &I) { DELEGATE(Instruction);}
// Next level propagators: If the user does not overload a specific
// instruction type, they can overload one of these to get the whole class
// of instructions...
RetTy visitCastInst(CastInst &I) { DELEGATE(UnaryInstruction);}
RetTy visitUnaryOperator(UnaryOperator &I) { DELEGATE(UnaryInstruction);}
RetTy visitBinaryOperator(BinaryOperator &I) { DELEGATE(Instruction);}
RetTy visitCmpInst(CmpInst &I) { DELEGATE(Instruction);}
RetTy visitUnaryInstruction(UnaryInstruction &I){ DELEGATE(Instruction);}
// The next level delegation for `CallBase` is slightly more complex in order
// to support visiting cases where the call is also a terminator.
RetTy visitCallBase(CallBase &I) {
if (isa<InvokeInst>(I) || isa<CallBrInst>(I))
return static_cast<SubClass *>(this)->visitTerminator(I);
// Provide a legacy visitor for a 'callsite' that visits calls, invokes,
// and calbrs.
// Prefer overriding the type system based `CallBase` instead.
RetTy visitCallSite(CallSite CS) {
Instruction &I = *CS.getInstruction();
// If the user wants a 'default' case, they can choose to override this
// function. If this function is not overloaded in the user's subclass, then
// this instruction just gets ignored.
// Note that you MUST override this function if your return type is not void.
void visitInstruction(Instruction &I) {} // Ignore unhandled instructions
// Special helper function to delegate to CallInst subclass visitors.
RetTy delegateCallInst(CallInst &I) {
if (const Function *F = I.getCalledFunction()) {
switch (F->getIntrinsicID()) {
default: DELEGATE(IntrinsicInst);
case Intrinsic::dbg_declare: DELEGATE(DbgDeclareInst);
case Intrinsic::dbg_value: DELEGATE(DbgValueInst);
case Intrinsic::dbg_label: DELEGATE(DbgLabelInst);
case Intrinsic::memcpy: DELEGATE(MemCpyInst);
case Intrinsic::memmove: DELEGATE(MemMoveInst);
case Intrinsic::memset: DELEGATE(MemSetInst);
case Intrinsic::vastart: DELEGATE(VAStartInst);
case Intrinsic::vaend: DELEGATE(VAEndInst);
case Intrinsic::vacopy: DELEGATE(VACopyInst);
case Intrinsic::not_intrinsic: break;
// An overload that will never actually be called, it is used only from dead
// code in the dispatching from opcodes to instruction subclasses.
RetTy delegateCallInst(Instruction &I) {
llvm_unreachable("delegateCallInst called for non-CallInst");
} // End llvm namespace