LCOV - code coverage report
Current view: top level - lib/Analysis - AssumptionCache.cpp (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 108 110 98.2 %
Date: 2017-09-14 15:23:50 Functions: 18 18 100.0 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : //===- AssumptionCache.cpp - Cache finding @llvm.assume calls -------------===//
       2             : //
       3             : //                     The LLVM Compiler Infrastructure
       4             : //
       5             : // This file is distributed under the University of Illinois Open Source
       6             : // License. See LICENSE.TXT for details.
       7             : //
       8             : //===----------------------------------------------------------------------===//
       9             : //
      10             : // This file contains a pass that keeps track of @llvm.assume intrinsics in
      11             : // the functions of a module.
      12             : //
      13             : //===----------------------------------------------------------------------===//
      14             : 
      15             : #include "llvm/Analysis/AssumptionCache.h"
      16             : #include "llvm/ADT/STLExtras.h"
      17             : #include "llvm/ADT/SmallPtrSet.h"
      18             : #include "llvm/ADT/SmallVector.h"
      19             : #include "llvm/IR/BasicBlock.h"
      20             : #include "llvm/IR/Function.h"
      21             : #include "llvm/IR/InstrTypes.h"
      22             : #include "llvm/IR/Instruction.h"
      23             : #include "llvm/IR/Instructions.h"
      24             : #include "llvm/IR/Intrinsics.h"
      25             : #include "llvm/IR/PassManager.h"
      26             : #include "llvm/IR/PatternMatch.h"
      27             : #include "llvm/Pass.h"
      28             : #include "llvm/Support/Casting.h"
      29             : #include "llvm/Support/CommandLine.h"
      30             : #include "llvm/Support/ErrorHandling.h"
      31             : #include "llvm/Support/raw_ostream.h"
      32             : #include <algorithm>
      33             : #include <cassert>
      34             : #include <utility>
      35             : 
      36             : using namespace llvm;
      37             : using namespace llvm::PatternMatch;
      38             : 
      39             : static cl::opt<bool>
      40       72306 :     VerifyAssumptionCache("verify-assumption-cache", cl::Hidden,
      41      216918 :                           cl::desc("Enable verification of assumption cache"),
      42      289224 :                           cl::init(false));
      43             : 
      44             : SmallVector<WeakTrackingVH, 1> &
      45        7321 : AssumptionCache::getOrInsertAffectedValues(Value *V) {
      46             :   // Try using find_as first to avoid creating extra value handles just for the
      47             :   // purpose of doing the lookup.
      48        7321 :   auto AVI = AffectedValues.find_as(V);
      49       21963 :   if (AVI != AffectedValues.end())
      50        3508 :     return AVI->second;
      51             : 
      52             :   auto AVIP = AffectedValues.insert(
      53       22878 :       {AffectedValueCallbackVH(V, this), SmallVector<WeakTrackingVH, 1>()});
      54        3813 :   return AVIP.first->second;
      55             : }
      56             : 
      57        3588 : void AssumptionCache::updateAffectedValues(CallInst *CI) {
      58             :   // Note: This code must be kept in-sync with the code in
      59             :   // computeKnownBitsFromAssume in ValueTracking.
      60             : 
      61        7176 :   SmallVector<Value *, 16> Affected;
      62       18075 :   auto AddAffected = [&Affected](Value *V) {
      63       21538 :     if (isa<Argument>(V)) {
      64         182 :       Affected.push_back(V);
      65       17608 :     } else if (auto *I = dyn_cast<Instruction>(V)) {
      66        7021 :       Affected.push_back(I);
      67             : 
      68             :       // Peek through unary operators to find the source of the condition.
      69             :       Value *Op;
      70       35105 :       if (match(I, m_BitCast(m_Value(Op))) ||
      71       42037 :           match(I, m_PtrToInt(m_Value(Op))) ||
      72       27817 :           match(I, m_Not(m_Value(Op)))) {
      73         280 :         if (isa<Instruction>(Op) || isa<Argument>(Op))
      74         103 :           Affected.push_back(Op);
      75             :       }
      76             :     }
      77       14357 :   };
      78             : 
      79        7176 :   Value *Cond = CI->getArgOperand(0), *A, *B;
      80        3588 :   AddAffected(Cond);
      81             : 
      82             :   CmpInst::Predicate Pred;
      83       14218 :   if (match(Cond, m_ICmp(Pred, m_Value(A), m_Value(B)))) {
      84        3454 :     AddAffected(A);
      85        3454 :     AddAffected(B);
      86             : 
      87        3454 :     if (Pred == ICmpInst::ICMP_EQ) {
      88             :       // For equality comparisons, we handle the case of bit inversion.
      89         649 :       auto AddAffectedFromEq = [&AddAffected](Value *V) {
      90             :         Value *A;
      91        1128 :         if (match(V, m_Not(m_Value(A)))) {
      92           2 :           AddAffected(A);
      93           2 :           V = A;
      94             :         }
      95             : 
      96             :         Value *B;
      97             :         ConstantInt *C;
      98             :         // (A & B) or (A | B) or (A ^ B).
      99        1504 :         if (match(V, m_BitwiseLogic(m_Value(A), m_Value(B)))) {
     100         134 :           AddAffected(A);
     101         134 :           AddAffected(B);
     102             :         // (A << C) or (A >>_s C) or (A >>_u C) where C is some constant.
     103         968 :         } else if (match(V, m_Shift(m_Value(A), m_ConstantInt(C)))) {
     104           3 :           AddAffected(A);
     105             :         }
     106         564 :       };
     107             : 
     108         188 :       AddAffectedFromEq(A);
     109         188 :       AddAffectedFromEq(B);
     110             :     }
     111             :   }
     112             : 
     113       18070 :   for (auto &AV : Affected) {
     114        7306 :     auto &AVV = getOrInsertAffectedValues(AV);
     115       29224 :     if (std::find(AVV.begin(), AVV.end(), CI) == AVV.end())
     116       21060 :       AVV.push_back(CI);
     117             :   }
     118        3588 : }
     119             : 
     120          48 : void AssumptionCache::AffectedValueCallbackVH::deleted() {
     121         144 :   auto AVI = AC->AffectedValues.find(getValPtr());
     122         144 :   if (AVI != AC->AffectedValues.end())
     123          48 :     AC->AffectedValues.erase(AVI);
     124             :   // 'this' now dangles!
     125          48 : }
     126             : 
     127          15 : void AssumptionCache::copyAffectedValuesInCache(Value *OV, Value *NV) {
     128          15 :   auto &NAVV = getOrInsertAffectedValues(NV);
     129          45 :   auto AVI = AffectedValues.find(OV);
     130          45 :   if (AVI == AffectedValues.end())
     131           0 :     return;
     132             : 
     133          60 :   for (auto &A : AVI->second)
     134          60 :     if (std::find(NAVV.begin(), NAVV.end(), A) == NAVV.end())
     135          15 :       NAVV.push_back(A);
     136             : }
     137             : 
     138          29 : void AssumptionCache::AffectedValueCallbackVH::allUsesReplacedWith(Value *NV) {
     139          72 :   if (!isa<Instruction>(NV) && !isa<Argument>(NV))
     140             :     return;
     141             : 
     142             :   // Any assumptions that affected this value now affect the new value.
     143             : 
     144          15 :   AC->copyAffectedValuesInCache(getValPtr(), NV);
     145             :   // 'this' now might dangle! If the AffectedValues map was resized to add an
     146             :   // entry for NV then this object might have been destroyed in favor of some
     147             :   // copy in the grown map.
     148             : }
     149             : 
     150       85032 : void AssumptionCache::scanFunction() {
     151             :   assert(!Scanned && "Tried to scan the function twice!");
     152             :   assert(AssumeHandles.empty() && "Already have assumes when scanning!");
     153             : 
     154             :   // Go through all instructions in all blocks, add all calls to @llvm.assume
     155             :   // to this cache.
     156      659279 :   for (BasicBlock &B : F)
     157     3823261 :     for (Instruction &II : B)
     158     3096236 :       if (match(&II, m_Intrinsic<Intrinsic::assume>()))
     159       10140 :         AssumeHandles.push_back(&II);
     160             : 
     161             :   // Mark the scan as complete.
     162       85032 :   Scanned = true;
     163             : 
     164             :   // Update affected values.
     165      258476 :   for (auto &A : AssumeHandles)
     166        3380 :     updateAffectedValues(cast<CallInst>(A));
     167       85032 : }
     168             : 
     169        7089 : void AssumptionCache::registerAssumption(CallInst *CI) {
     170             :   assert(match(CI, m_Intrinsic<Intrinsic::assume>()) &&
     171             :          "Registered call does not call @llvm.assume");
     172             : 
     173             :   // If we haven't scanned the function yet, just drop this assumption. It will
     174             :   // be found when we scan later.
     175        7089 :   if (!Scanned)
     176             :     return;
     177             : 
     178         177 :   AssumeHandles.push_back(CI);
     179             : 
     180             : #ifndef NDEBUG
     181             :   assert(CI->getParent() &&
     182             :          "Cannot register @llvm.assume call not in a basic block");
     183             :   assert(&F == CI->getParent()->getParent() &&
     184             :          "Cannot register @llvm.assume call not in this function");
     185             : 
     186             :   // We expect the number of assumptions to be small, so in an asserts build
     187             :   // check that we don't accumulate duplicates and that all assumptions point
     188             :   // to the same function.
     189             :   SmallPtrSet<Value *, 16> AssumptionSet;
     190             :   for (auto &VH : AssumeHandles) {
     191             :     if (!VH)
     192             :       continue;
     193             : 
     194             :     assert(&F == cast<Instruction>(VH)->getParent()->getParent() &&
     195             :            "Cached assumption not inside this function!");
     196             :     assert(match(cast<CallInst>(VH), m_Intrinsic<Intrinsic::assume>()) &&
     197             :            "Cached something other than a call to @llvm.assume!");
     198             :     assert(AssumptionSet.insert(VH).second &&
     199             :            "Cache contains multiple copies of a call!");
     200             :   }
     201             : #endif
     202             : 
     203          59 :   updateAffectedValues(CI);
     204             : }
     205             : 
     206             : AnalysisKey AssumptionAnalysis::Key;
     207             : 
     208           1 : PreservedAnalyses AssumptionPrinterPass::run(Function &F,
     209             :                                              FunctionAnalysisManager &AM) {
     210           1 :   AssumptionCache &AC = AM.getResult<AssumptionAnalysis>(F);
     211             : 
     212           1 :   OS << "Cached assumptions for function: " << F.getName() << "\n";
     213           6 :   for (auto &VH : AC.assumptions())
     214           3 :     if (VH)
     215          12 :       OS << "  " << *cast<CallInst>(VH)->getArgOperand(0) << "\n";
     216             : 
     217           1 :   return PreservedAnalyses::all();
     218             : }
     219             : 
     220       62545 : void AssumptionCacheTracker::FunctionCallbackVH::deleted() {
     221      125090 :   auto I = ACT->AssumptionCaches.find_as(cast<Function>(getValPtr()));
     222      187635 :   if (I != ACT->AssumptionCaches.end())
     223       62545 :     ACT->AssumptionCaches.erase(I);
     224             :   // 'this' now dangles!
     225       62545 : }
     226             : 
     227     3142870 : AssumptionCache &AssumptionCacheTracker::getAssumptionCache(Function &F) {
     228             :   // We probe the function map twice to try and avoid creating a value handle
     229             :   // around the function in common cases. This makes insertion a bit slower,
     230             :   // but if we have to insert we're going to scan the whole function so that
     231             :   // shouldn't matter.
     232     3142870 :   auto I = AssumptionCaches.find_as(&F);
     233     9428610 :   if (I != AssumptionCaches.end())
     234     5714508 :     return *I->second;
     235             : 
     236             :   // Ok, build a new cache by scanning the function, insert it and the value
     237             :   // handle into our map, and return the newly populated cache.
     238      571232 :   auto IP = AssumptionCaches.insert(std::make_pair(
     239     1142464 :       FunctionCallbackVH(&F, this), llvm::make_unique<AssumptionCache>(F)));
     240             :   assert(IP.second && "Scanning function already in the map?");
     241      571232 :   return *IP.first->second;
     242             : }
     243             : 
     244       76696 : void AssumptionCacheTracker::verifyAnalysis() const {
     245             :   // FIXME: In the long term the verifier should not be controllable with a
     246             :   // flag. We should either fix all passes to correctly update the assumption
     247             :   // cache and enable the verifier unconditionally or somehow arrange for the
     248             :   // assumption list to be updated automatically by passes.
     249       76696 :   if (!VerifyAssumptionCache)
     250       76695 :     return;
     251             : 
     252           2 :   SmallPtrSet<const CallInst *, 4> AssumptionSet;
     253           2 :   for (const auto &I : AssumptionCaches) {
     254           7 :     for (auto &VH : I.second->assumptions())
     255           2 :       if (VH)
     256           2 :         AssumptionSet.insert(cast<CallInst>(VH));
     257             : 
     258          11 :     for (const BasicBlock &B : cast<Function>(*I.first))
     259          40 :       for (const Instruction &II : B)
     260          32 :         if (match(&II, m_Intrinsic<Intrinsic::assume>()) &&
     261           2 :             !AssumptionSet.count(cast<CallInst>(&II)))
     262           0 :           report_fatal_error("Assumption in scanned function not in cache");
     263             :   }
     264             : }
     265             : 
     266       89892 : AssumptionCacheTracker::AssumptionCacheTracker() : ImmutablePass(ID) {
     267       29964 :   initializeAssumptionCacheTrackerPass(*PassRegistry::getPassRegistry());
     268       29964 : }
     269             : 
     270             : AssumptionCacheTracker::~AssumptionCacheTracker() = default;
     271             : 
     272             : char AssumptionCacheTracker::ID = 0;
     273             : 
     274     3220672 : INITIALIZE_PASS(AssumptionCacheTracker, "assumption-cache-tracker",
     275             :                 "Assumption Cache Tracker", false, true)

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