// removeAttribute() currently does not work on Attribute::Alignment
// (it fails with an assertion error), so we have to take a more
// convoluted route to removing this attribute by recreating the
// AttributeSet.
AttributeSet RemoveAttrs(LLVMContext &Context, AttributeSet Attrs) {
SmallVector<AttributeSet, 8> AttrList;
for (unsigned Slot = 0; Slot < Attrs.getNumSlots(); ++Slot) {
unsigned Index = Attrs.getSlotIndex(Slot);
AttrBuilder AB;
for (AttributeSet::iterator Attr = Attrs.begin(Slot), E = Attrs.end(Slot);
Attr != E; ++Attr) {
if (Attr->isEnumAttribute() &&
Attr->getKindAsEnum() != Attribute::ByVal &&
Attr->getKindAsEnum() != Attribute::StructRet) {
AB.addAttribute(*Attr);
}
// IR semantics require that ByVal implies NoAlias. However, IR
// semantics do not require StructRet to imply NoAlias. For
// example, a global variable address can be passed as a
// StructRet argument, although Clang does not do so and Clang
// explicitly adds NoAlias to StructRet arguments.
if (Attr->isEnumAttribute() &&
Attr->getKindAsEnum() == Attribute::ByVal) {
AB.addAttribute(Attribute::get(Context, Attribute::NoAlias));
}
}
AttrList.push_back(AttributeSet::get(Context, Index, AB));
}
return AttributeSet::get(Context, AttrList);
}
// Most attributes are just hints which can safely be removed. A few
// attributes can break programs if removed, so check all attributes
// before removing them, in case LLVM adds new attributes.
static void CheckAttributes(AttributeSet Attrs) {
for (unsigned Slot = 0; Slot < Attrs.getNumSlots(); ++Slot) {
for (AttributeSet::iterator Attr = Attrs.begin(Slot), E = Attrs.end(Slot);
Attr != E; ++Attr) {
if (!Attr->isEnumAttribute()) {
continue;
}
switch (Attr->getKindAsEnum()) {
// The following attributes can affect calling conventions.
// Rather than complaining, we just strip these out.
// ExpandSmallArguments should have rendered SExt/ZExt
// meaningless since the function arguments will be at least
// 32-bit.
case Attribute::InReg:
case Attribute::SExt:
case Attribute::ZExt:
// These attributes influence ABI decisions that should not be
// visible to PNaCl pexes.
case Attribute::NonLazyBind: // Only relevant to dynamic linking.
case Attribute::NoRedZone:
case Attribute::StackAlignment:
// The following attributes are just hints, which can be
// safely removed.
case Attribute::AlwaysInline:
case Attribute::InlineHint:
case Attribute::MinSize:
case Attribute::NoAlias:
case Attribute::NoBuiltin:
case Attribute::NoCapture:
case Attribute::NoDuplicate:
case Attribute::NoImplicitFloat:
case Attribute::NoInline:
case Attribute::NoReturn:
case Attribute::OptimizeForSize:
case Attribute::ReadNone:
case Attribute::ReadOnly:
// PNaCl does not support -fstack-protector in the translator.
case Attribute::StackProtect:
case Attribute::StackProtectReq:
case Attribute::StackProtectStrong:
// PNaCl does not support ASan in the translator.
case Attribute::SanitizeAddress:
case Attribute::SanitizeThread:
case Attribute::SanitizeMemory:
// The Language References cites setjmp() as an example of a
// function which returns twice, and says ReturnsTwice is
// necessary to disable optimizations such as tail calls.
// However, in the PNaCl ABI, setjmp() is an intrinsic, and
// user-defined functions are not allowed to return twice.
case Attribute::ReturnsTwice:
// NoUnwind is not a hint if it causes unwind info to be
// omitted, since this will prevent C++ exceptions from
// propagating. In the future, when PNaCl supports zero-cost
// C++ exception handling using unwind info, we might allow
// NoUnwind and UWTable. Alternatively, we might continue to
// disallow them, and just generate unwind info for all
// functions.
case Attribute::NoUnwind:
case Attribute::UWTable:
break;
case Attribute::ByVal:
case Attribute::StructRet:
case Attribute::Alignment:
Attrs.dump();
report_fatal_error(
"Attribute should already have been removed by ExpandByVal");
case Attribute::Naked:
case Attribute::Nest:
Attrs.dump();
report_fatal_error("Unsupported attribute");
default:
Attrs.dump();
report_fatal_error("Unrecognized attribute");
}
}
}
}