forked from OSchip/llvm-project
83 lines
3.1 KiB
C++
83 lines
3.1 KiB
C++
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//===- BitSetUtils.cpp - Utilities related to pointer bitsets -------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains functions that make it easier to manipulate bitsets for
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// devirtualization.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/BitSetUtils.h"
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#include "llvm/IR/Intrinsics.h"
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#include "llvm/IR/Module.h"
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using namespace llvm;
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// Search for virtual calls that call FPtr and add them to DevirtCalls.
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static void
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findCallsAtConstantOffset(SmallVectorImpl<DevirtCallSite> &DevirtCalls,
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Value *FPtr, uint64_t Offset) {
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for (const Use &U : FPtr->uses()) {
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Value *User = U.getUser();
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if (isa<BitCastInst>(User)) {
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findCallsAtConstantOffset(DevirtCalls, User, Offset);
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} else if (auto CI = dyn_cast<CallInst>(User)) {
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DevirtCalls.push_back({Offset, CI});
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} else if (auto II = dyn_cast<InvokeInst>(User)) {
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DevirtCalls.push_back({Offset, II});
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}
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}
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}
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// Search for virtual calls that load from VPtr and add them to DevirtCalls.
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static void
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findLoadCallsAtConstantOffset(Module *M,
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SmallVectorImpl<DevirtCallSite> &DevirtCalls,
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Value *VPtr, uint64_t Offset) {
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for (const Use &U : VPtr->uses()) {
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Value *User = U.getUser();
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if (isa<BitCastInst>(User)) {
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findLoadCallsAtConstantOffset(M, DevirtCalls, User, Offset);
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} else if (isa<LoadInst>(User)) {
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findCallsAtConstantOffset(DevirtCalls, User, Offset);
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} else if (auto GEP = dyn_cast<GetElementPtrInst>(User)) {
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// Take into account the GEP offset.
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if (VPtr == GEP->getPointerOperand() && GEP->hasAllConstantIndices()) {
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SmallVector<Value *, 8> Indices(GEP->op_begin() + 1, GEP->op_end());
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uint64_t GEPOffset = M->getDataLayout().getIndexedOffsetInType(
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GEP->getSourceElementType(), Indices);
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findLoadCallsAtConstantOffset(M, DevirtCalls, User, Offset + GEPOffset);
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}
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}
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}
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}
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void llvm::findDevirtualizableCalls(
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SmallVectorImpl<DevirtCallSite> &DevirtCalls,
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SmallVectorImpl<CallInst *> &Assumes, CallInst *CI) {
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assert(CI->getCalledFunction()->getIntrinsicID() == Intrinsic::bitset_test);
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Module *M = CI->getParent()->getParent()->getParent();
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// Find llvm.assume intrinsics for this llvm.bitset.test call.
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for (const Use &CIU : CI->uses()) {
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auto AssumeCI = dyn_cast<CallInst>(CIU.getUser());
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if (AssumeCI) {
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Function *F = AssumeCI->getCalledFunction();
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if (F && F->getIntrinsicID() == Intrinsic::assume)
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Assumes.push_back(AssumeCI);
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}
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}
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// If we found any, search for virtual calls based on %p and add them to
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// DevirtCalls.
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if (!Assumes.empty())
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findLoadCallsAtConstantOffset(M, DevirtCalls,
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CI->getArgOperand(0)->stripPointerCasts(), 0);
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}
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