forked from OSchip/llvm-project
300 lines
9.9 KiB
C++
300 lines
9.9 KiB
C++
//===- AssumptionCache.cpp - Cache finding @llvm.assume calls -------------===//
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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 contains a pass that keeps track of @llvm.assume intrinsics in
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// the functions of a module.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/AssumptionCache.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/InstrTypes.h"
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#include "llvm/IR/Instruction.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/Intrinsics.h"
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#include "llvm/IR/PassManager.h"
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#include "llvm/IR/PatternMatch.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/Casting.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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#include <algorithm>
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#include <cassert>
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#include <utility>
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using namespace llvm;
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using namespace llvm::PatternMatch;
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static cl::opt<bool>
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VerifyAssumptionCache("verify-assumption-cache", cl::Hidden,
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cl::desc("Enable verification of assumption cache"),
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cl::init(false));
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SmallVector<WeakTrackingVH, 1> &
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AssumptionCache::getOrInsertAffectedValues(Value *V) {
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// Try using find_as first to avoid creating extra value handles just for the
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// purpose of doing the lookup.
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auto AVI = AffectedValues.find_as(V);
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if (AVI != AffectedValues.end())
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return AVI->second;
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auto AVIP = AffectedValues.insert(
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{AffectedValueCallbackVH(V, this), SmallVector<WeakTrackingVH, 1>()});
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return AVIP.first->second;
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}
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static void findAffectedValues(CallInst *CI,
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SmallVectorImpl<Value *> &Affected) {
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// Note: This code must be kept in-sync with the code in
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// computeKnownBitsFromAssume in ValueTracking.
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auto AddAffected = [&Affected](Value *V) {
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if (isa<Argument>(V)) {
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Affected.push_back(V);
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} else if (auto *I = dyn_cast<Instruction>(V)) {
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Affected.push_back(I);
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// Peek through unary operators to find the source of the condition.
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Value *Op;
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if (match(I, m_BitCast(m_Value(Op))) ||
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match(I, m_PtrToInt(m_Value(Op))) ||
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match(I, m_Not(m_Value(Op)))) {
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if (isa<Instruction>(Op) || isa<Argument>(Op))
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Affected.push_back(Op);
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}
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}
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};
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Value *Cond = CI->getArgOperand(0), *A, *B;
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AddAffected(Cond);
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CmpInst::Predicate Pred;
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if (match(Cond, m_ICmp(Pred, m_Value(A), m_Value(B)))) {
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AddAffected(A);
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AddAffected(B);
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if (Pred == ICmpInst::ICMP_EQ) {
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// For equality comparisons, we handle the case of bit inversion.
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auto AddAffectedFromEq = [&AddAffected](Value *V) {
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Value *A;
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if (match(V, m_Not(m_Value(A)))) {
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AddAffected(A);
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V = A;
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}
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Value *B;
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ConstantInt *C;
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// (A & B) or (A | B) or (A ^ B).
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if (match(V, m_BitwiseLogic(m_Value(A), m_Value(B)))) {
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AddAffected(A);
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AddAffected(B);
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// (A << C) or (A >>_s C) or (A >>_u C) where C is some constant.
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} else if (match(V, m_Shift(m_Value(A), m_ConstantInt(C)))) {
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AddAffected(A);
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}
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};
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AddAffectedFromEq(A);
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AddAffectedFromEq(B);
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}
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}
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}
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void AssumptionCache::updateAffectedValues(CallInst *CI) {
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SmallVector<Value *, 16> Affected;
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findAffectedValues(CI, Affected);
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for (auto &AV : Affected) {
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auto &AVV = getOrInsertAffectedValues(AV);
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if (std::find(AVV.begin(), AVV.end(), CI) == AVV.end())
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AVV.push_back(CI);
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}
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}
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void AssumptionCache::unregisterAssumption(CallInst *CI) {
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SmallVector<Value *, 16> Affected;
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findAffectedValues(CI, Affected);
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for (auto &AV : Affected) {
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auto AVI = AffectedValues.find_as(AV);
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if (AVI != AffectedValues.end())
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AffectedValues.erase(AVI);
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}
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remove_if(AssumeHandles, [CI](WeakTrackingVH &VH) { return CI == VH; });
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}
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void AssumptionCache::AffectedValueCallbackVH::deleted() {
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auto AVI = AC->AffectedValues.find(getValPtr());
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if (AVI != AC->AffectedValues.end())
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AC->AffectedValues.erase(AVI);
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// 'this' now dangles!
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}
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void AssumptionCache::transferAffectedValuesInCache(Value *OV, Value *NV) {
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auto &NAVV = getOrInsertAffectedValues(NV);
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auto AVI = AffectedValues.find(OV);
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if (AVI == AffectedValues.end())
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return;
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for (auto &A : AVI->second)
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if (std::find(NAVV.begin(), NAVV.end(), A) == NAVV.end())
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NAVV.push_back(A);
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AffectedValues.erase(OV);
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}
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void AssumptionCache::AffectedValueCallbackVH::allUsesReplacedWith(Value *NV) {
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if (!isa<Instruction>(NV) && !isa<Argument>(NV))
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return;
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// Any assumptions that affected this value now affect the new value.
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AC->transferAffectedValuesInCache(getValPtr(), NV);
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// 'this' now might dangle! If the AffectedValues map was resized to add an
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// entry for NV then this object might have been destroyed in favor of some
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// copy in the grown map.
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}
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void AssumptionCache::scanFunction() {
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assert(!Scanned && "Tried to scan the function twice!");
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assert(AssumeHandles.empty() && "Already have assumes when scanning!");
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// Go through all instructions in all blocks, add all calls to @llvm.assume
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// to this cache.
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for (BasicBlock &B : F)
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for (Instruction &II : B)
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if (match(&II, m_Intrinsic<Intrinsic::assume>()))
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AssumeHandles.push_back(&II);
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// Mark the scan as complete.
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Scanned = true;
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// Update affected values.
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for (auto &A : AssumeHandles)
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updateAffectedValues(cast<CallInst>(A));
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}
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void AssumptionCache::registerAssumption(CallInst *CI) {
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assert(match(CI, m_Intrinsic<Intrinsic::assume>()) &&
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"Registered call does not call @llvm.assume");
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// If we haven't scanned the function yet, just drop this assumption. It will
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// be found when we scan later.
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if (!Scanned)
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return;
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AssumeHandles.push_back(CI);
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#ifndef NDEBUG
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assert(CI->getParent() &&
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"Cannot register @llvm.assume call not in a basic block");
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assert(&F == CI->getParent()->getParent() &&
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"Cannot register @llvm.assume call not in this function");
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// We expect the number of assumptions to be small, so in an asserts build
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// check that we don't accumulate duplicates and that all assumptions point
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// to the same function.
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SmallPtrSet<Value *, 16> AssumptionSet;
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for (auto &VH : AssumeHandles) {
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if (!VH)
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continue;
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assert(&F == cast<Instruction>(VH)->getParent()->getParent() &&
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"Cached assumption not inside this function!");
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assert(match(cast<CallInst>(VH), m_Intrinsic<Intrinsic::assume>()) &&
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"Cached something other than a call to @llvm.assume!");
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assert(AssumptionSet.insert(VH).second &&
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"Cache contains multiple copies of a call!");
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}
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#endif
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updateAffectedValues(CI);
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}
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AnalysisKey AssumptionAnalysis::Key;
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PreservedAnalyses AssumptionPrinterPass::run(Function &F,
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FunctionAnalysisManager &AM) {
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AssumptionCache &AC = AM.getResult<AssumptionAnalysis>(F);
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OS << "Cached assumptions for function: " << F.getName() << "\n";
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for (auto &VH : AC.assumptions())
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if (VH)
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OS << " " << *cast<CallInst>(VH)->getArgOperand(0) << "\n";
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return PreservedAnalyses::all();
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}
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void AssumptionCacheTracker::FunctionCallbackVH::deleted() {
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auto I = ACT->AssumptionCaches.find_as(cast<Function>(getValPtr()));
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if (I != ACT->AssumptionCaches.end())
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ACT->AssumptionCaches.erase(I);
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// 'this' now dangles!
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}
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AssumptionCache &AssumptionCacheTracker::getAssumptionCache(Function &F) {
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// We probe the function map twice to try and avoid creating a value handle
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// around the function in common cases. This makes insertion a bit slower,
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// but if we have to insert we're going to scan the whole function so that
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// shouldn't matter.
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auto I = AssumptionCaches.find_as(&F);
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if (I != AssumptionCaches.end())
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return *I->second;
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// Ok, build a new cache by scanning the function, insert it and the value
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// handle into our map, and return the newly populated cache.
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auto IP = AssumptionCaches.insert(std::make_pair(
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FunctionCallbackVH(&F, this), std::make_unique<AssumptionCache>(F)));
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assert(IP.second && "Scanning function already in the map?");
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return *IP.first->second;
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}
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AssumptionCache *AssumptionCacheTracker::lookupAssumptionCache(Function &F) {
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auto I = AssumptionCaches.find_as(&F);
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if (I != AssumptionCaches.end())
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return I->second.get();
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return nullptr;
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}
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void AssumptionCacheTracker::verifyAnalysis() const {
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// FIXME: In the long term the verifier should not be controllable with a
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// flag. We should either fix all passes to correctly update the assumption
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// cache and enable the verifier unconditionally or somehow arrange for the
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// assumption list to be updated automatically by passes.
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if (!VerifyAssumptionCache)
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return;
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SmallPtrSet<const CallInst *, 4> AssumptionSet;
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for (const auto &I : AssumptionCaches) {
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for (auto &VH : I.second->assumptions())
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if (VH)
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AssumptionSet.insert(cast<CallInst>(VH));
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for (const BasicBlock &B : cast<Function>(*I.first))
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for (const Instruction &II : B)
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if (match(&II, m_Intrinsic<Intrinsic::assume>()) &&
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!AssumptionSet.count(cast<CallInst>(&II)))
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report_fatal_error("Assumption in scanned function not in cache");
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}
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}
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AssumptionCacheTracker::AssumptionCacheTracker() : ImmutablePass(ID) {
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initializeAssumptionCacheTrackerPass(*PassRegistry::getPassRegistry());
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}
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AssumptionCacheTracker::~AssumptionCacheTracker() = default;
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char AssumptionCacheTracker::ID = 0;
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INITIALIZE_PASS(AssumptionCacheTracker, "assumption-cache-tracker",
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"Assumption Cache Tracker", false, true)
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