TypeMetadataUtils.h

Go to the documentation of this file.

//===- TypeMetadataUtils.h - Utilities related to type metadata --*- C++ -*-==//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains functions that make it easier to manipulate type metadata
// for devirtualization.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_ANALYSIS_TYPEMETADATAUTILS_H
#define LLVM_ANALYSIS_TYPEMETADATAUTILS_H
 
#include "llvm/ADT/SmallVector.h"
#include <cstdint>
 
namespace llvm {
 
class CallBase;
class CallInst;
class Constant;
class DominatorTree;
class Instruction;
class Module;
 
/// The type of CFI jumptable needed for a function.
enum CfiFunctionLinkage {
  CFL_Definition = 0,
  CFL_Declaration = 1,
  CFL_WeakDeclaration = 2
};
 
/// A call site that could be devirtualized.
struct DevirtCallSite {
  /// The offset from the address point to the virtual function.
  uint64_t Offset;
  /// The call site itself.
  CallBase &CB;
};
 
/// Given a call to the intrinsic \@llvm.type.test, find all devirtualizable
/// call sites based on the call and return them in DevirtCalls.
void findDevirtualizableCallsForTypeTest(
    SmallVectorImpl<DevirtCallSite> &DevirtCalls,
    SmallVectorImpl<CallInst *> &Assumes, const CallInst *CI,
    DominatorTree &DT);
 
/// Given a call to the intrinsic \@llvm.type.checked.load, find all
/// devirtualizable call sites based on the call and return them in DevirtCalls.
void findDevirtualizableCallsForTypeCheckedLoad(
    SmallVectorImpl<DevirtCallSite> &DevirtCalls,
    SmallVectorImpl<Instruction *> &LoadedPtrs,
    SmallVectorImpl<Instruction *> &Preds, bool &HasNonCallUses,
    const CallInst *CI, DominatorTree &DT);
 
// Processes a Constant recursively looking into elements of arrays, structs and
// expressions to find a trivial pointer element that is located at the given
// offset (relative to the beginning of the whole outer Constant).
//
// Used for example from GlobalDCE to find an entry in a C++ vtable that matches
// a vcall offset.
//
// To support Swift vtables, getPointerAtOffset can see through "relative
// pointers", i.e. (sub-)expressions of the form of:
//
//   @symbol = ... {
//     i32 trunc (i64 sub (
//       i64 ptrtoint (<type> @target to i64), i64 ptrtoint (... @symbol to i64)
//     ) to i32)
//   }
//
// For such (sub-)expressions, getPointerAtOffset returns the @target pointer.
Constant *getPointerAtOffset(Constant *I, uint64_t Offset, Module &M,
                             Constant *TopLevelGlobal = nullptr);
}
 
#endif