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thirdparty/capstone/suite/synctools/tablegen/include/llvm/IR/AbstractCallSite.h

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+//===- AbstractCallSite.h - Abstract call sites -----------------*- 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 defines the AbstractCallSite class, which is a is a wrapper that
+// allows treating direct, indirect, and callback calls the same.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_IR_ABSTRACTCALLSITE_H
+#define LLVM_IR_ABSTRACTCALLSITE_H
+
+#include "llvm/IR/Argument.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/InstrTypes.h"
+#include "llvm/IR/Use.h"
+#include "llvm/IR/Value.h"
+#include "llvm/Support/Casting.h"
+#include <cassert>
+
+namespace llvm {
+
+/// AbstractCallSite
+///
+/// An abstract call site is a wrapper that allows to treat direct,
+/// indirect, and callback calls the same. If an abstract call site
+/// represents a direct or indirect call site it behaves like a stripped
+/// down version of a normal call site object. The abstract call site can
+/// also represent a callback call, thus the fact that the initially
+/// called function (=broker) may invoke a third one (=callback callee).
+/// In this case, the abstract call site hides the middle man, hence the
+/// broker function. The result is a representation of the callback call,
+/// inside the broker, but in the context of the original call to the broker.
+///
+/// There are up to three functions involved when we talk about callback call
+/// sites. The caller (1), which invokes the broker function. The broker
+/// function (2), that will invoke the callee zero or more times. And finally
+/// the callee (3), which is the target of the callback call.
+///
+/// The abstract call site will handle the mapping from parameters to arguments
+/// depending on the semantic of the broker function. However, it is important
+/// to note that the mapping is often partial. Thus, some arguments of the
+/// call/invoke instruction are mapped to parameters of the callee while others
+/// are not.
+class AbstractCallSite {
+public:
+
+  /// The encoding of a callback with regards to the underlying instruction.
+  struct CallbackInfo {
+
+    /// For direct/indirect calls the parameter encoding is empty. If it is not,
+    /// the abstract call site represents a callback. In that case, the first
+    /// element of the encoding vector represents which argument of the call
+    /// site CB is the callback callee. The remaining elements map parameters
+    /// (identified by their position) to the arguments that will be passed
+    /// through (also identified by position but in the call site instruction).
+    ///
+    /// NOTE that we use LLVM argument numbers (starting at 0) and not
+    /// clang/source argument numbers (starting at 1). The -1 entries represent
+    /// unknown values that are passed to the callee.
+    using ParameterEncodingTy = SmallVector<int, 0>;
+    ParameterEncodingTy ParameterEncoding;
+
+  };
+
+private:
+
+  /// The underlying call site:
+  ///   caller -> callee,             if this is a direct or indirect call site
+  ///   caller -> broker function,    if this is a callback call site
+  CallBase *CB;
+
+  /// The encoding of a callback with regards to the underlying instruction.
+  CallbackInfo CI;
+
+public:
+  /// Sole constructor for abstract call sites (ACS).
+  ///
+  /// An abstract call site can only be constructed through a llvm::Use because
+  /// each operand (=use) of an instruction could potentially be a different
+  /// abstract call site. Furthermore, even if the value of the llvm::Use is the
+  /// same, and the user is as well, the abstract call sites might not be.
+  ///
+  /// If a use is not associated with an abstract call site the constructed ACS
+  /// will evaluate to false if converted to a boolean.
+  ///
+  /// If the use is the callee use of a call or invoke instruction, the
+  /// constructed abstract call site will behave as a llvm::CallSite would.
+  ///
+  /// If the use is not a callee use of a call or invoke instruction, the
+  /// callback metadata is used to determine the argument <-> parameter mapping
+  /// as well as the callee of the abstract call site.
+  AbstractCallSite(const Use *U);
+
+  /// Add operand uses of \p CB that represent callback uses into
+  /// \p CallbackUses.
+  ///
+  /// All uses added to \p CallbackUses can be used to create abstract call
+  /// sites for which AbstractCallSite::isCallbackCall() will return true.
+  static void getCallbackUses(const CallBase &CB,
+                              SmallVectorImpl<const Use *> &CallbackUses);
+
+  /// Conversion operator to conveniently check for a valid/initialized ACS.
+  explicit operator bool() const { return CB != nullptr; }
+
+  /// Return the underlying instruction.
+  CallBase *getInstruction() const { return CB; }
+
+  /// Return true if this ACS represents a direct call.
+  bool isDirectCall() const {
+    return !isCallbackCall() && !CB->isIndirectCall();
+  }
+
+  /// Return true if this ACS represents an indirect call.
+  bool isIndirectCall() const {
+    return !isCallbackCall() && CB->isIndirectCall();
+  }
+
+  /// Return true if this ACS represents a callback call.
+  bool isCallbackCall() const {
+    // For a callback call site the callee is ALWAYS stored first in the
+    // transitive values vector. Thus, a non-empty vector indicates a callback.
+    return !CI.ParameterEncoding.empty();
+  }
+
+  /// Return true if @p UI is the use that defines the callee of this ACS.
+  bool isCallee(Value::const_user_iterator UI) const {
+    return isCallee(&UI.getUse());
+  }
+
+  /// Return true if @p U is the use that defines the callee of this ACS.
+  bool isCallee(const Use *U) const {
+    if (isDirectCall())
+      return CB->isCallee(U);
+
+    assert(!CI.ParameterEncoding.empty() &&
+           "Callback without parameter encoding!");
+
+    // If the use is actually in a constant cast expression which itself
+    // has only one use, we look through the constant cast expression.
+    if (auto *CE = dyn_cast<ConstantExpr>(U->getUser()))
+      if (CE->hasOneUse() && CE->isCast())
+        U = &*CE->use_begin();
+
+    return (int)CB->getArgOperandNo(U) == CI.ParameterEncoding[0];
+  }
+
+  /// Return the number of parameters of the callee.
+  unsigned getNumArgOperands() const {
+    if (isDirectCall())
+      return CB->arg_size();
+    // Subtract 1 for the callee encoding.
+    return CI.ParameterEncoding.size() - 1;
+  }
+
+  /// Return the operand index of the underlying instruction associated with @p
+  /// Arg.
+  int getCallArgOperandNo(Argument &Arg) const {
+    return getCallArgOperandNo(Arg.getArgNo());
+  }
+
+  /// Return the operand index of the underlying instruction associated with
+  /// the function parameter number @p ArgNo or -1 if there is none.
+  int getCallArgOperandNo(unsigned ArgNo) const {
+    if (isDirectCall())
+      return ArgNo;
+    // Add 1 for the callee encoding.
+    return CI.ParameterEncoding[ArgNo + 1];
+  }
+
+  /// Return the operand of the underlying instruction associated with @p Arg.
+  Value *getCallArgOperand(Argument &Arg) const {
+    return getCallArgOperand(Arg.getArgNo());
+  }
+
+  /// Return the operand of the underlying instruction associated with the
+  /// function parameter number @p ArgNo or nullptr if there is none.
+  Value *getCallArgOperand(unsigned ArgNo) const {
+    if (isDirectCall())
+      return CB->getArgOperand(ArgNo);
+    // Add 1 for the callee encoding.
+    return CI.ParameterEncoding[ArgNo + 1] >= 0
+               ? CB->getArgOperand(CI.ParameterEncoding[ArgNo + 1])
+               : nullptr;
+  }
+
+  /// Return the operand index of the underlying instruction associated with the
+  /// callee of this ACS. Only valid for callback calls!
+  int getCallArgOperandNoForCallee() const {
+    assert(isCallbackCall());
+    assert(CI.ParameterEncoding.size() && CI.ParameterEncoding[0] >= 0);
+    return CI.ParameterEncoding[0];
+  }
+
+  /// Return the use of the callee value in the underlying instruction. Only
+  /// valid for callback calls!
+  const Use &getCalleeUseForCallback() const {
+    int CalleeArgIdx = getCallArgOperandNoForCallee();
+    assert(CalleeArgIdx >= 0 &&
+           unsigned(CalleeArgIdx) < getInstruction()->getNumOperands());
+    return getInstruction()->getOperandUse(CalleeArgIdx);
+  }
+
+  /// Return the pointer to function that is being called.
+  Value *getCalledOperand() const {
+    if (isDirectCall())
+      return CB->getCalledOperand();
+    return CB->getArgOperand(getCallArgOperandNoForCallee());
+  }
+
+  /// Return the function being called if this is a direct call, otherwise
+  /// return null (if it's an indirect call).
+  Function *getCalledFunction() const {
+    Value *V = getCalledOperand();
+    return V ? dyn_cast<Function>(V->stripPointerCasts()) : nullptr;
+  }
+};
+
+/// Apply function Func to each CB's callback call site.
+template <typename UnaryFunction>
+void forEachCallbackCallSite(const CallBase &CB, UnaryFunction Func) {
+  SmallVector<const Use *, 4u> CallbackUses;
+  AbstractCallSite::getCallbackUses(CB, CallbackUses);
+  for (const Use *U : CallbackUses) {
+    AbstractCallSite ACS(U);
+    assert(ACS && ACS.isCallbackCall() && "must be a callback call");
+    Func(ACS);
+  }
+}
+
+/// Apply function Func to each CB's callback function.
+template <typename UnaryFunction>
+void forEachCallbackFunction(const CallBase &CB, UnaryFunction Func) {
+  forEachCallbackCallSite(CB, [&Func](AbstractCallSite &ACS) {
+    if (Function *Callback = ACS.getCalledFunction())
+      Func(Callback);
+  });
+}
+
+} // end namespace llvm
+
+#endif // LLVM_IR_ABSTRACTCALLSITE_H