[llvm] r291859 - [asan] Don't overalign global metadata.

[Hans Wennborg via llvm-commits]

Merged in r292802.

Thanks,
Hans

On Thu, Jan 19, 2017 at 4:18 PM, Kuba Mracek via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Please merge this (along with r291858 which this depends on) into release_40.
>
> Thanks,
> Kuba
>
>> On 12 Jan 2017, at 15:26, Evgeniy Stepanov via llvm-commits <llvm-commits at lists.llvm.org> wrote:
>>
>> Author: eugenis
>> Date: Thu Jan 12 17:26:20 2017
>> New Revision: 291859
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=291859&view=rev
>> Log:
>> [asan] Don't overalign global metadata.
>>
>> Other than on COFF with incremental linking, global metadata should
>> not need any extra alignment.
>>
>> Differential Revision: https://reviews.llvm.org/D28628
>>
>> Modified:
>>    llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp
>>    llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata_darwin.ll
>>
>> Modified: llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp?rev=291859&r1=291858&r2=291859&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp (original)
>> +++ llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp Thu Jan 12 17:26:20 2017
>> @@ -1609,22 +1609,12 @@ void AddressSanitizerModule::SetComdatFo
>> GlobalVariable *
>> AddressSanitizerModule::CreateMetadataGlobal(Module &M, Constant *Initializer,
>>                                              StringRef OriginalName) {
>> -  auto &DL = M.getDataLayout();
>>   GlobalVariable *Metadata =
>>       new GlobalVariable(M, Initializer->getType(), false,
>>                          GlobalVariable::InternalLinkage, Initializer,
>>                          Twine("__asan_global_") +
>>                              GlobalValue::getRealLinkageName(OriginalName));
>>   Metadata->setSection(getGlobalMetadataSection());
>> -
>> -  // We don't want any padding, but we also need a reasonable alignment.
>> -  // The MSVC linker always inserts padding when linking incrementally. We
>> -  // cope with that by aligning each struct to its size, which must be a power
>> -  // of two.
>> -  unsigned SizeOfGlobalStruct = DL.getTypeAllocSize(Initializer->getType());
>> -  assert(isPowerOf2_32(SizeOfGlobalStruct) &&
>> -         "global metadata will not be padded appropriately");
>> -  Metadata->setAlignment(SizeOfGlobalStruct);
>>   return Metadata;
>> }
>>
>> @@ -1642,11 +1632,22 @@ void AddressSanitizerModule::InstrumentG
>>     IRBuilder<> &IRB, Module &M, ArrayRef<GlobalVariable *> ExtendedGlobals,
>>     ArrayRef<Constant *> MetadataInitializers) {
>>   assert(ExtendedGlobals.size() == MetadataInitializers.size());
>> +  auto &DL = M.getDataLayout();
>>
>>   for (size_t i = 0; i < ExtendedGlobals.size(); i++) {
>> +    Constant *Initializer = MetadataInitializers[i];
>>     GlobalVariable *G = ExtendedGlobals[i];
>>     GlobalVariable *Metadata =
>> -        CreateMetadataGlobal(M, MetadataInitializers[i], G->getName());
>> +        CreateMetadataGlobal(M, Initializer, G->getName());
>> +
>> +    // The MSVC linker always inserts padding when linking incrementally. We
>> +    // cope with that by aligning each struct to its size, which must be a power
>> +    // of two.
>> +    unsigned SizeOfGlobalStruct = DL.getTypeAllocSize(Initializer->getType());
>> +    assert(isPowerOf2_32(SizeOfGlobalStruct) &&
>> +           "global metadata will not be padded appropriately");
>> +    Metadata->setAlignment(SizeOfGlobalStruct);
>> +
>>     SetComdatForGlobalMetadata(G, Metadata);
>>   }
>> }
>>
>> Modified: llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata_darwin.ll
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata_darwin.ll?rev=291859&r1=291858&r2=291859&view=diff
>> ==============================================================================
>> --- llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata_darwin.ll (original)
>> +++ llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata_darwin.ll Thu Jan 12 17:26:20 2017
>> @@ -16,7 +16,7 @@ target triple = "x86_64-apple-macosx10.1
>>
>>
>> ; Find the metadata for @global:
>> -; CHECK: [[METADATA:@.+]] = internal global {{.*}} @global {{.*}} section "__DATA,__asan_globals,regular", align 64
>> +; CHECK: [[METADATA:@.+]] = internal global {{.*}} @global {{.*}} section "__DATA,__asan_globals,regular"
>>
>> ; Find the liveness binder for @global and its metadata:
>> ; CHECK: @__asan_binder_global = internal global {{.*}} @global {{.*}} [[METADATA]] {{.*}} section "__DATA,__asan_liveness,regular,live_support"
>>
>>
>> _______________________________________________
>> llvm-commits mailing list
>> llvm-commits at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>
> _______________________________________________
> llvm-commits mailing list
> llvm-commits at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits