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//===-- 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/IR/AbstractCallSite.h"
#include "llvm/ADT/Statistic.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)");
void AbstractCallSite::getCallbackUses(
const CallBase &CB, SmallVectorImpl<const Use *> &CallbackUses) {
const Function *Callee = CB.getCalledFunction();
if (!Callee)
return;
MDNode *CallbackMD = Callee->getMetadata(LLVMContext::MD_callback);
if (!CallbackMD)
return;
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 < CB.arg_size())
CallbackUses.push_back(CB.arg_begin() + CBCalleeIdx);
}
}
/// Create an abstract call site from a use.
AbstractCallSite::AbstractCallSite(const Use *U)
: CB(dyn_cast<CallBase>(U->getUser())) {
// First handle unknown users.
if (!CB) {
// 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 CB accordingly.
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U->getUser()))
if (CE->hasOneUse() && CE->isCast()) {
U = &*CE->use_begin();
CB = dyn_cast<CallBase>(U->getUser());
}
if (!CB) {
NumInvalidAbstractCallSitesUnknownUse++;
return;
}
}
// Then handle direct or indirect calls. Thus, if U is the callee of the
// call site CB it is not a callback and we are done.
if (CB->isCallee(U)) {
NumDirectAbstractCallSites++;
return;
}
// If we cannot identify the broker function we cannot create a callback and
// invalidate the abstract call site.
Function *Callee = CB->getCalledFunction();
if (!Callee) {
NumInvalidAbstractCallSitesUnknownCallee++;
CB = nullptr;
return;
}
MDNode *CallbackMD = Callee->getMetadata(LLVMContext::MD_callback);
if (!CallbackMD) {
NumInvalidAbstractCallSitesNoCallback++;
CB = nullptr;
return;
}
unsigned UseIdx = CB->getArgOperandNo(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++;
CB = nullptr;
return;
}
NumCallbackCallSites++;
assert(CallbackEncMD->getNumOperands() >= 2 && "Incomplete !callback metadata");
unsigned NumCallOperands = CB->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);
}
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