[llvm] r224146 - IR: Don't track nullptr on metadata RAUW

[Philip Reames]

Oops, sorry.  I was expecting an IR file and didn't read closely enough.

On 12/12/2014 02:57 PM, Duncan P. N. Exon Smith wrote:
> See: unittests/IR/MetadataTest.cpp
>
>> On 2014 Dec 12, at 14:54, Philip Reames <listmail at philipreames.com> wrote:
>>
>> Test case?
>>
>> On 12/12/2014 11:24 AM, Duncan P. N. Exon Smith wrote:
>>> Author: dexonsmith
>>> Date: Fri Dec 12 13:24:33 2014
>>> New Revision: 224146
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=224146&view=rev
>>> Log:
>>> IR: Don't track nullptr on metadata RAUW
>>>
>>> The RAUW support in `Metadata` supports going to `nullptr` specifically
>>> to handle values being deleted, causing `ValueAsMetadata` to be deleted.
>>>
>>> Fix the case where the reference is from a `TrackingMDRef` (as opposed
>>> to an `MDOperand` or a `MetadataAsValue`).
>>>
>>> This is surprisingly rare -- metadata tracked by `TrackingMDRef` going
>>> to null -- but it came up in an openSUSE bootstrap during inlining.  The
>>> tracking ref was held by the `ValueMap` because it was referencing a
>>> local, the basic block containing the local became dead after it had
>>> been merged in, and when the local was deleted, the tracking ref
>>> asserted in an `isa`.
>>>
>>> Modified:
>>>      llvm/trunk/lib/IR/Metadata.cpp
>>>      llvm/trunk/unittests/IR/MetadataTest.cpp
>>>
>>> Modified: llvm/trunk/lib/IR/Metadata.cpp
>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Metadata.cpp?rev=224146&r1=224145&r2=224146&view=diff
>>> ==============================================================================
>>> --- llvm/trunk/lib/IR/Metadata.cpp (original)
>>> +++ llvm/trunk/lib/IR/Metadata.cpp Fri Dec 12 13:24:33 2014
>>> @@ -173,7 +173,8 @@ void ReplaceableMetadataImpl::replaceAll
>>>         // Update unowned tracking references directly.
>>>         Metadata *&Ref = *static_cast<Metadata **>(Pair.first);
>>>         Ref = MD;
>>> -      MetadataTracking::track(Ref);
>>> +      if (MD)
>>> +        MetadataTracking::track(Ref);
>>>         UseMap.erase(Pair.first);
>>>         continue;
>>>       }
>>>
>>> Modified: llvm/trunk/unittests/IR/MetadataTest.cpp
>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/IR/MetadataTest.cpp?rev=224146&r1=224145&r2=224146&view=diff
>>> ==============================================================================
>>> --- llvm/trunk/unittests/IR/MetadataTest.cpp (original)
>>> +++ llvm/trunk/unittests/IR/MetadataTest.cpp Fri Dec 12 13:24:33 2014
>>> @@ -207,6 +207,53 @@ TEST_F(MetadataAsValueTest, MDNodeConsta
>>>     EXPECT_EQ(V, V2);
>>>   }
>>>   +typedef MetadataTest ValueAsMetadataTest;
>>> +
>>> +TEST_F(ValueAsMetadataTest, UpdatesOnRAUW) {
>>> +  Type *Ty = Type::getInt1PtrTy(Context);
>>> +  std::unique_ptr<GlobalVariable> GV0(
>>> +      new GlobalVariable(Ty, false, GlobalValue::ExternalLinkage));
>>> +  auto *MD = ValueAsMetadata::get(GV0.get());
>>> +  EXPECT_TRUE(MD->getValue() == GV0.get());
>>> +  ASSERT_TRUE(GV0->use_empty());
>>> +
>>> +  std::unique_ptr<GlobalVariable> GV1(
>>> +      new GlobalVariable(Ty, false, GlobalValue::ExternalLinkage));
>>> +  GV0->replaceAllUsesWith(GV1.get());
>>> +  EXPECT_TRUE(MD->getValue() == GV1.get());
>>> +}
>>> +
>>> +typedef MetadataTest TrackingMDRefTest;
>>> +
>>> +TEST_F(TrackingMDRefTest, UpdatesOnRAUW) {
>>> +  Type *Ty = Type::getInt1PtrTy(Context);
>>> +  std::unique_ptr<GlobalVariable> GV0(
>>> +      new GlobalVariable(Ty, false, GlobalValue::ExternalLinkage));
>>> +  TypedTrackingMDRef<ValueAsMetadata> MD(ValueAsMetadata::get(GV0.get()));
>>> +  EXPECT_TRUE(MD->getValue() == GV0.get());
>>> +  ASSERT_TRUE(GV0->use_empty());
>>> +
>>> +  std::unique_ptr<GlobalVariable> GV1(
>>> +      new GlobalVariable(Ty, false, GlobalValue::ExternalLinkage));
>>> +  GV0->replaceAllUsesWith(GV1.get());
>>> +  EXPECT_TRUE(MD->getValue() == GV1.get());
>>> +
>>> +  // Reset it, so we don't inadvertently test deletion.
>>> +  MD.reset();
>>> +}
>>> +
>>> +TEST_F(TrackingMDRefTest, UpdatesOnDeletion) {
>>> +  Type *Ty = Type::getInt1PtrTy(Context);
>>> +  std::unique_ptr<GlobalVariable> GV(
>>> +      new GlobalVariable(Ty, false, GlobalValue::ExternalLinkage));
>>> +  TypedTrackingMDRef<ValueAsMetadata> MD(ValueAsMetadata::get(GV.get()));
>>> +  EXPECT_TRUE(MD->getValue() == GV.get());
>>> +  ASSERT_TRUE(GV->use_empty());
>>> +
>>> +  GV.reset();
>>> +  EXPECT_TRUE(!MD);
>>> +}
>>> +
>>>   TEST(NamedMDNodeTest, Search) {
>>>     LLVMContext Context;
>>>     ConstantAsMetadata *C =
>>>
>>>
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