r196997 - [ms-abi] Makes Virtual Base Alignment Look at All Virtual Bases

[Warren Hunt]

There will be a format normalizing pass on the Microsoft Record Layout
Builder at some point in future (likely right after the fuzzer stops
finding bugs).  The formatting of all of Record Layout is mixed and I
inherited some of that.

-Warren


On Tue, Dec 10, 2013 at 8:00 PM, David Majnemer <david.majnemer at gmail.com>wrote:

>
>
>
> On Tue, Dec 10, 2013 at 6:21 PM, Warren Hunt <whunt at google.com> wrote:
>
>> Author: whunt
>> Date: Tue Dec 10 20:21:03 2013
>> New Revision: 196997
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=196997&view=rev
>> Log:
>> [ms-abi] Makes Virtual Base Alignment Look at All Virtual Bases
>>
>> Prior to this patch, the alignment imposed by virtual bases only
>> included direct virtual bases.  This patch fixes it to look at all
>> virtual bases.
>>
>>
>> Modified:
>>     cfe/trunk/lib/AST/RecordLayoutBuilder.cpp
>>     cfe/trunk/test/Layout/ms-x86-pack-and-align.cpp
>>
>> Modified: cfe/trunk/lib/AST/RecordLayoutBuilder.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/RecordLayoutBuilder.cpp?rev=196997&r1=196996&r2=196997&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/AST/RecordLayoutBuilder.cpp (original)
>> +++ cfe/trunk/lib/AST/RecordLayoutBuilder.cpp Tue Dec 10 20:21:03 2013
>> @@ -2125,8 +2125,6 @@ public:
>>    /// \brief The alignment of the non-virtual portion of the record
>> layout
>>    /// Only used for C++ layouts.
>>    CharUnits NonVirtualAlignment;
>> -  /// \brief The additional alignment imposed by the virtual bases.
>> -  CharUnits VirtualAlignment;
>>    /// \brief The primary base class (if one exists).
>>    const CXXRecordDecl *PrimaryBase;
>>    /// \brief The class we share our vb-pointer with.
>> @@ -2265,7 +2263,6 @@ MicrosoftRecordLayoutBuilder::initialize
>>    HasExtendableVFPtr = false;
>>    SharedVBPtrBase = 0;
>>    PrimaryBase = 0;
>> -  VirtualAlignment = CharUnits::One();
>>    LeadsWithZeroSizedBase = false;
>>
>>    // If the record has a dynamic base class, attempt to choose a primary
>> base
>> @@ -2285,7 +2282,6 @@ MicrosoftRecordLayoutBuilder::initialize
>>        HasZeroSizedSubObject = true;
>>      // Handle virtual bases.
>>      if (i->isVirtual()) {
>> -      VirtualAlignment = std::max(VirtualAlignment,
>> getBaseAlignment(Layout));
>>        HasVBPtr = true;
>>        continue;
>>      }
>> @@ -2555,7 +2551,14 @@ void MicrosoftRecordLayoutBuilder::layou
>>    if (!HasVBPtr)
>>      return;
>>
>> -  updateAlignment(VirtualAlignment);
>> +  for (CXXRecordDecl::base_class_const_iterator i = RD->vbases_begin(),
>> +                                                e = RD->vbases_end();
>> +       i != e; ++i) {
>>
>
> I'd make 'i' and 'e' capital seeing as how they are actually class types.
>
>
>> +    const CXXRecordDecl *BaseDecl =
>> +
>>  cast<CXXRecordDecl>(i->getType()->getAs<RecordType>()->getDecl());
>>
>
> I think this could be I->getType->getAsCXXRecordDecl()->getDecl()
>
>
>> +    const ASTRecordLayout &Layout = Context.getASTRecordLayout(BaseDecl);
>> +    updateAlignment(getBaseAlignment(Layout));
>> +  }
>>    PreviousBaseLayout = 0;
>>
>>    // Zero-sized v-bases obey the alignment attribute so apply it here.
>>  The
>>
>> Modified: cfe/trunk/test/Layout/ms-x86-pack-and-align.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Layout/ms-x86-pack-and-align.cpp?rev=196997&r1=196996&r2=196997&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/Layout/ms-x86-pack-and-align.cpp (original)
>> +++ cfe/trunk/test/Layout/ms-x86-pack-and-align.cpp Tue Dec 10 20:21:03
>> 2013
>> @@ -114,7 +114,32 @@ struct Z : virtual B {
>>
>>  #pragma pack(pop)
>>
>> +struct A1 { long long a; };
>> +#pragma pack(push, 1)
>> +struct B1 : virtual A1 { char a; };
>> +#pragma pack(pop)
>> +struct C1 : B1 {};
>> +// CHECK: *** Dumping AST Record Layout
>> +// CHECK:    0 | struct C1
>> +// CHECK:    0 |   struct B1 (base)
>> +// CHECK:    0 |     (B1 vbtable pointer)
>> +// CHECK:    4 |     char a
>> +// CHECK:    8 |   struct A1 (virtual base)
>> +// CHECK:    8 |     long long a
>> +// CHECK:      | [sizeof=16, align=8
>> +// CHECK:      |  nvsize=5, nvalign=1]
>> +// CHECK-X64: *** Dumping AST Record Layout
>> +// CHECK-X64:    0 | struct C1
>> +// CHECK-X64:    0 |   struct B1 (base)
>> +// CHECK-X64:    0 |     (B1 vbtable pointer)
>> +// CHECK-X64:    8 |     char a
>> +// CHECK-X64:   16 |   struct A1 (virtual base)
>> +// CHECK-X64:   16 |     long long a
>> +// CHECK-X64:      | [sizeof=24, align=8
>> +// CHECK-X64:      |  nvsize=9, nvalign=1]
>> +
>>  int a[
>>  sizeof(X)+
>>  sizeof(Y)+
>> -sizeof(Z)];
>> +sizeof(Z)+
>> +sizeof(C1)];
>>
>>
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>
>
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