Commit 481bb249 authored by Hans Wennborg's avatar Hans Wennborg
Browse files

Merging r292133: 

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r292133 | hfinkel | 2017-01-16 07:22:01 -0800 (Mon, 16 Jan 2017) | 10 lines

Fix use-after-free bug in AffectedValueCallbackVH::allUsesReplacedWith

When transferring affected values in the cache from an old value, identified by
the value of the current callback, to the specified new value we might need to
insert a new entry into the DenseMap which constitutes the cache. Doing so
might delete the current callback object. Move the copying logic into a new
function, a member of the assumption cache itself, so that we don't run into UB
should the callback handle itself be removed mid-copy.

Differential Revision: https://reviews.llvm.org/D28749
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llvm-svn: 292312
parent 57f962df

llvm/include/llvm/Analysis/AssumptionCache.h

+4 −1
Original line number Diff line number Diff line
@@ -68,7 +68,10 @@ class AssumptionCache { 
  AffectedValuesMap AffectedValues;



  /// Get the vector of assumptions which affect a value from the cache.

  SmallVector<WeakVH, 1> &getAffectedValues(Value *V);

  SmallVector<WeakVH, 1> &getOrInsertAffectedValues(Value *V);



  /// Copy affected values in the cache for OV to be affected values for NV.

  void copyAffectedValuesInCache(Value *OV, Value *NV);



  /// \brief Flag tracking whether we have scanned the function yet.

  ///

llvm/lib/Analysis/AssumptionCache.cpp

+17 −10
Original line number Diff line number Diff line
@@ -24,7 +24,7 @@ 
using namespace llvm;

using namespace llvm::PatternMatch;



SmallVector<WeakVH, 1> &AssumptionCache::getAffectedValues(Value *V) {

SmallVector<WeakVH, 1> &AssumptionCache::getOrInsertAffectedValues(Value *V) {

  // Try using find_as first to avoid creating extra value handles just for the

  // purpose of doing the lookup.

  auto AVI = AffectedValues.find_as(V);
@@ -98,7 +98,7 @@ void AssumptionCache::updateAffectedValues(CallInst *CI) { 
  }



  for (auto &AV : Affected) {

    auto &AVV = getAffectedValues(AV);

    auto &AVV = getOrInsertAffectedValues(AV);

    if (std::find(AVV.begin(), AVV.end(), CI) == AVV.end())

      AVV.push_back(CI);

  }
@@ -111,20 +111,27 @@ void AssumptionCache::AffectedValueCallbackVH::deleted() { 
  // 'this' now dangles!

}



void AssumptionCache::copyAffectedValuesInCache(Value *OV, Value *NV) {

  auto &NAVV = getOrInsertAffectedValues(NV);

  auto AVI = AffectedValues.find(OV);

  if (AVI == AffectedValues.end())

    return;



  for (auto &A : AVI->second)

    if (std::find(NAVV.begin(), NAVV.end(), A) == NAVV.end())

      NAVV.push_back(A);

}



void AssumptionCache::AffectedValueCallbackVH::allUsesReplacedWith(Value *NV) {

  if (!isa<Instruction>(NV) && !isa<Argument>(NV))

    return;



  // Any assumptions that affected this value now affect the new value.



  auto &NAVV = AC->getAffectedValues(NV);

  auto AVI = AC->AffectedValues.find(getValPtr());

  if (AVI == AC->AffectedValues.end())

    return;



  for (auto &A : AVI->second)

    if (std::find(NAVV.begin(), NAVV.end(), A) == NAVV.end())

      NAVV.push_back(A);

  AC->copyAffectedValuesInCache(getValPtr(), NV);

  // 'this' now might dangle! If the AffectedValues map was resized to add an

  // entry for NV then this object might have been destroyed in favor of some

  // copy in the grown map.

}



void AssumptionCache::scanFunction() {