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135 lines
4.5 KiB
C++
135 lines
4.5 KiB
C++
//===-- AbstractCallSite.cpp - Implementation of abstract call sites ------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements abstract call sites which unify the interface for
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// direct, indirect, and callback call sites.
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//
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// For more information see:
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// https://llvm.org/devmtg/2018-10/talk-abstracts.html#talk20
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/StringSwitch.h"
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#include "llvm/IR/CallSite.h"
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#include "llvm/Support/Debug.h"
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using namespace llvm;
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#define DEBUG_TYPE "abstract-call-sites"
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STATISTIC(NumCallbackCallSites, "Number of callback call sites created");
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STATISTIC(NumDirectAbstractCallSites,
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"Number of direct abstract call sites created");
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STATISTIC(NumInvalidAbstractCallSitesUnknownUse,
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"Number of invalid abstract call sites created (unknown use)");
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STATISTIC(NumInvalidAbstractCallSitesUnknownCallee,
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"Number of invalid abstract call sites created (unknown callee)");
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STATISTIC(NumInvalidAbstractCallSitesNoCallback,
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"Number of invalid abstract call sites created (no callback)");
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/// Create an abstract call site from a use.
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AbstractCallSite::AbstractCallSite(const Use *U) : CS(U->getUser()) {
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// First handle unknown users.
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if (!CS) {
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// If the use is actually in a constant cast expression which itself
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// has only one use, we look through the constant cast expression.
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// This happens by updating the use @p U to the use of the constant
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// cast expression and afterwards re-initializing CS accordingly.
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if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U->getUser()))
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if (CE->getNumUses() == 1 && CE->isCast()) {
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U = &*CE->use_begin();
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CS = CallSite(U->getUser());
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}
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if (!CS) {
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NumInvalidAbstractCallSitesUnknownUse++;
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return;
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}
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}
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// Then handle direct or indirect calls. Thus, if U is the callee of the
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// call site CS it is not a callback and we are done.
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if (CS.isCallee(U)) {
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NumDirectAbstractCallSites++;
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return;
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}
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// If we cannot identify the broker function we cannot create a callback and
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// invalidate the abstract call site.
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Function *Callee = CS.getCalledFunction();
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if (!Callee) {
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NumInvalidAbstractCallSitesUnknownCallee++;
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CS = CallSite();
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return;
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}
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MDNode *CallbackMD = Callee->getMetadata(LLVMContext::MD_callback);
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if (!CallbackMD) {
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NumInvalidAbstractCallSitesNoCallback++;
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CS = CallSite();
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return;
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}
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unsigned UseIdx = CS.getArgumentNo(U);
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MDNode *CallbackEncMD = nullptr;
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for (const MDOperand &Op : CallbackMD->operands()) {
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MDNode *OpMD = cast<MDNode>(Op.get());
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auto *CBCalleeIdxAsCM = cast<ConstantAsMetadata>(OpMD->getOperand(0));
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uint64_t CBCalleeIdx =
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cast<ConstantInt>(CBCalleeIdxAsCM->getValue())->getZExtValue();
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if (CBCalleeIdx != UseIdx)
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continue;
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CallbackEncMD = OpMD;
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break;
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}
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if (!CallbackEncMD) {
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NumInvalidAbstractCallSitesNoCallback++;
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CS = CallSite();
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return;
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}
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NumCallbackCallSites++;
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assert(CallbackEncMD->getNumOperands() >= 2 && "Incomplete !callback metadata");
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unsigned NumCallOperands = CS.getNumArgOperands();
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// Skip the var-arg flag at the end when reading the metadata.
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for (unsigned u = 0, e = CallbackEncMD->getNumOperands() - 1; u < e; u++) {
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Metadata *OpAsM = CallbackEncMD->getOperand(u).get();
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auto *OpAsCM = cast<ConstantAsMetadata>(OpAsM);
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assert(OpAsCM->getType()->isIntegerTy(64) &&
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"Malformed !callback metadata");
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int64_t Idx = cast<ConstantInt>(OpAsCM->getValue())->getSExtValue();
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assert(-1 <= Idx && Idx <= NumCallOperands &&
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"Out-of-bounds !callback metadata index");
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CI.ParameterEncoding.push_back(Idx);
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}
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if (!Callee->isVarArg())
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return;
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Metadata *VarArgFlagAsM =
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CallbackEncMD->getOperand(CallbackEncMD->getNumOperands() - 1).get();
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auto *VarArgFlagAsCM = cast<ConstantAsMetadata>(VarArgFlagAsM);
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assert(VarArgFlagAsCM->getType()->isIntegerTy(1) &&
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"Malformed !callback metadata var-arg flag");
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if (VarArgFlagAsCM->getValue()->isNullValue())
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return;
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// Add all variadic arguments at the end.
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for (unsigned u = Callee->arg_size(); u < NumCallOperands; u++)
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CI.ParameterEncoding.push_back(u);
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}
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