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Respect type alignment when choosing padding fields.

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Fixes ABI mismatch when e.g. padding a 28 byte union from a
20 byte member, where previously, an i64 would be emitted,
yielding a 32 byte LLVM struct size on ulong.alignof == 8
platforms.

Test case will follow on the 2.064 branch.
This commit is contained in:
David Nadlinger
2013-12-26 06:23:39 +01:00
parent 27ecc11915
commit f85d2a5a0a
4 changed files with 70 additions and 42 deletions
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48
ir/irtypestruct.cpp
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@@ -38,35 +38,51 @@ IrTypeStruct::IrTypeStruct(StructDeclaration * sd)
//////////////////////////////////////////////////////////////////////////////
size_t add_zeros(std::vector<llvm::Type*>& defaultTypes, size_t diff)
static bool isAligned(llvm::Type* type, size_t offset) {
return gDataLayout->getABITypeAlignment(type) % offset == 0;
}
size_t add_zeros(std::vector<llvm::Type*>& defaultTypes,
size_t startOffset, size_t endOffset)
{
size_t n = defaultTypes.size();
while (diff)
size_t const oldLength = defaultTypes.size();
llvm::Type* const eightByte = llvm::Type::getInt64Ty(gIR->context());
llvm::Type* const fourByte = llvm::Type::getInt32Ty(gIR->context());
llvm::Type* const twoByte = llvm::Type::getInt16Ty(gIR->context());
assert(startOffset <= endOffset);
size_t paddingLeft = endOffset - startOffset;
while (paddingLeft)
{
if (global.params.is64bit && diff % 8 == 0)
if (global.params.is64bit && paddingLeft >= 8 && isAligned(eightByte, startOffset))
{
defaultTypes.push_back(llvm::Type::getInt64Ty(gIR->context()));
diff -= 8;
defaultTypes.push_back(eightByte);
startOffset += 8;
}
else if (diff % 4 == 0)
else if (paddingLeft >= 4 && isAligned(fourByte, startOffset))
{
defaultTypes.push_back(llvm::Type::getInt32Ty(gIR->context()));
diff -= 4;
defaultTypes.push_back(fourByte);
startOffset += 4;
}
else if (diff % 2 == 0)
else if (paddingLeft >= 2 && isAligned(twoByte, startOffset))
{
defaultTypes.push_back(llvm::Type::getInt16Ty(gIR->context()));
diff -= 2;
defaultTypes.push_back(twoByte);
startOffset += 2;
}
else
{
defaultTypes.push_back(llvm::Type::getInt8Ty(gIR->context()));
diff -= 1;
startOffset += 1;
}
paddingLeft = endOffset - startOffset;
}
return defaultTypes.size() - n;
return defaultTypes.size() - oldLength;
}
bool var_offset_sort_cb(const VarDeclaration* v1, const VarDeclaration* v2)
{
if (v1 && v2)
@@ -209,7 +225,7 @@ IrTypeStruct* IrTypeStruct::get(StructDeclaration* sd)
// insert explicit padding?
if (alignedoffset < vd->offset)
{
field_index += add_zeros(defaultTypes, vd->offset - alignedoffset);
field_index += add_zeros(defaultTypes, alignedoffset, vd->offset);
}
// add default type
@@ -225,7 +241,7 @@ IrTypeStruct* IrTypeStruct::get(StructDeclaration* sd)
// tail padding?
if (offset < sd->structsize)
{
add_zeros(defaultTypes, sd->structsize - offset);
add_zeros(defaultTypes, offset, sd->structsize);
}
// set struct body