--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/IR/AbstractCallSite.cpp	Wed Aug 14 19:46:37 2019 +0900
@@ -0,0 +1,134 @@
+//===-- AbstractCallSite.cpp - Implementation of abstract call sites ------===//
+//
+// 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 implements abstract call sites which unify the interface for
+// direct, indirect, and callback call sites.
+//
+// For more information see:
+// https://llvm.org/devmtg/2018-10/talk-abstracts.html#talk20
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/StringSwitch.h"
+#include "llvm/IR/CallSite.h"
+#include "llvm/Support/Debug.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "abstract-call-sites"
+
+STATISTIC(NumCallbackCallSites, "Number of callback call sites created");
+STATISTIC(NumDirectAbstractCallSites,
+          "Number of direct abstract call sites created");
+STATISTIC(NumInvalidAbstractCallSitesUnknownUse,
+          "Number of invalid abstract call sites created (unknown use)");
+STATISTIC(NumInvalidAbstractCallSitesUnknownCallee,
+          "Number of invalid abstract call sites created (unknown callee)");
+STATISTIC(NumInvalidAbstractCallSitesNoCallback,
+          "Number of invalid abstract call sites created (no callback)");
+
+/// Create an abstract call site from a use.
+AbstractCallSite::AbstractCallSite(const Use *U) : CS(U->getUser()) {
+
+  // First handle unknown users.
+  if (!CS) {
+
+    // If the use is actually in a constant cast expression which itself
+    // has only one use, we look through the constant cast expression.
+    // This happens by updating the use @p U to the use of the constant
+    // cast expression and afterwards re-initializing CS accordingly.
+    if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U->getUser()))
+      if (CE->getNumUses() == 1 && CE->isCast()) {
+        U = &*CE->use_begin();
+        CS = CallSite(U->getUser());
+      }
+
+    if (!CS) {
+      NumInvalidAbstractCallSitesUnknownUse++;
+      return;
+    }
+  }
+
+  // Then handle direct or indirect calls. Thus, if U is the callee of the
+  // call site CS it is not a callback and we are done.
+  if (CS.isCallee(U)) {
+    NumDirectAbstractCallSites++;
+    return;
+  }
+
+  // If we cannot identify the broker function we cannot create a callback and
+  // invalidate the abstract call site.
+  Function *Callee = CS.getCalledFunction();
+  if (!Callee) {
+    NumInvalidAbstractCallSitesUnknownCallee++;
+    CS = CallSite();
+    return;
+  }
+
+  MDNode *CallbackMD = Callee->getMetadata(LLVMContext::MD_callback);
+  if (!CallbackMD) {
+    NumInvalidAbstractCallSitesNoCallback++;
+    CS = CallSite();
+    return;
+  }
+
+  unsigned UseIdx = CS.getArgumentNo(U);
+  MDNode *CallbackEncMD = nullptr;
+  for (const MDOperand &Op : CallbackMD->operands()) {
+    MDNode *OpMD = cast<MDNode>(Op.get());
+    auto *CBCalleeIdxAsCM = cast<ConstantAsMetadata>(OpMD->getOperand(0));
+    uint64_t CBCalleeIdx =
+        cast<ConstantInt>(CBCalleeIdxAsCM->getValue())->getZExtValue();
+    if (CBCalleeIdx != UseIdx)
+      continue;
+    CallbackEncMD = OpMD;
+    break;
+  }
+
+  if (!CallbackEncMD) {
+    NumInvalidAbstractCallSitesNoCallback++;
+    CS = CallSite();
+    return;
+  }
+
+  NumCallbackCallSites++;
+
+  assert(CallbackEncMD->getNumOperands() >= 2 && "Incomplete !callback metadata");
+
+  unsigned NumCallOperands = CS.getNumArgOperands();
+  // Skip the var-arg flag at the end when reading the metadata.
+  for (unsigned u = 0, e = CallbackEncMD->getNumOperands() - 1; u < e; u++) {
+    Metadata *OpAsM = CallbackEncMD->getOperand(u).get();
+    auto *OpAsCM = cast<ConstantAsMetadata>(OpAsM);
+    assert(OpAsCM->getType()->isIntegerTy(64) &&
+           "Malformed !callback metadata");
+
+    int64_t Idx = cast<ConstantInt>(OpAsCM->getValue())->getSExtValue();
+    assert(-1 <= Idx && Idx <= NumCallOperands &&
+           "Out-of-bounds !callback metadata index");
+
+    CI.ParameterEncoding.push_back(Idx);
+  }
+
+  if (!Callee->isVarArg())
+    return;
+
+  Metadata *VarArgFlagAsM =
+      CallbackEncMD->getOperand(CallbackEncMD->getNumOperands() - 1).get();
+  auto *VarArgFlagAsCM = cast<ConstantAsMetadata>(VarArgFlagAsM);
+  assert(VarArgFlagAsCM->getType()->isIntegerTy(1) &&
+         "Malformed !callback metadata var-arg flag");
+
+  if (VarArgFlagAsCM->getValue()->isNullValue())
+    return;
+
+  // Add all variadic arguments at the end.
+  for (unsigned u = Callee->arg_size(); u < NumCallOperands; u++)
+    CI.ParameterEncoding.push_back(u);
+}