Transitional API for extracting constants from Metadata. More...

Namespaces
namespace	detail

Functions
template<class X, class Y>
std::enable_if_t< detail::IsValidPointer< X, Y >::value, bool >	hasa (Y &&MD)
	Check whether Metadata has a Value.
template<class X, class Y>
std::enable_if_t< detail::IsValidReference< X, Y & >::value, bool >	hasa (Y &MD)
template<class X, class Y>
std::enable_if_t< detail::IsValidPointer< X, Y >::value, X * >	extract (Y &&MD)
	Extract a Value from Metadata.
template<class X, class Y>
std::enable_if_t< detail::IsValidReference< X, Y & >::value, X * >	extract (Y &MD)
template<class X, class Y>
std::enable_if_t< detail::IsValidPointer< X, Y >::value, X * >	extract_or_null (Y &&MD)
	Extract a Value from Metadata, allowing null.
template<class X, class Y>
std::enable_if_t< detail::IsValidPointer< X, Y >::value, X * >	dyn_extract (Y &&MD)
	Extract a Value from Metadata, if any.
template<class X, class Y>
std::enable_if_t< detail::IsValidPointer< X, Y >::value, X * >	dyn_extract_or_null (Y &&MD)
	Extract a Value from Metadata, if any, allowing null.

Detailed Description

Transitional API for extracting constants from Metadata.

This namespace contains transitional functions for metadata that points to Constants.

In prehistory – when metadata was a subclass of Value – MDNode operands could refer to any Value. There's was a lot of code like this:

MDNode *N = ...;

auto *CI = dyn_cast<ConstantInt>(N->getOperand(2));

llvm::MDNode

Metadata node.

Definition Metadata.h:1077

llvm::dyn_cast

decltype(auto) dyn_cast(const From &Val)

dyn_cast<X> - Return the argument parameter cast to the specified type.

Definition Casting.h:649

N

#define N

Now that Value and Metadata are in separate hierarchies, maintaining the semantics for isa(), cast(), dyn_cast() (etc.) requires three steps: cast in the Metadata hierarchy, extraction of the Value, and cast in the Value hierarchy. Besides creating boiler-plate, this requires subtle control flow changes.

The end-goal is to create a new type of metadata, called (e.g.) MDInt, so that metadata can refer to numbers without traversing a bridge to the Value hierarchy. In this final state, the code above would look like this:

MDNode *N = ...;

auto *MI = dyn_cast<MDInt>(N->getOperand(2));

MI

IRTranslator LLVM IR MI

Definition IRTranslator.cpp:110

The API in this namespace supports the transition. MDInt doesn't exist yet, and even once it does, changing each metadata schema to use it is its own mini-project. In the meantime this API prevents us from introducing complex and bug-prone control flow that will disappear in the end. In particular, the above code looks like this:

MDNode *N = ...;

auto *CI = mdconst::dyn_extract<ConstantInt>(N->getOperand(2));

llvm::mdconst::dyn_extract

std::enable_if_t< detail::IsValidPointer< X, Y >::value, X * > dyn_extract(Y &&MD)

Extract a Value from Metadata, if any.

Definition Metadata.h:694

The full set of provided functions includes:

mdconst::hasa <=> isa mdconst::extract <=> cast mdconst::extract_or_null <=> cast_or_null mdconst::dyn_extract <=> dyn_cast mdconst::dyn_extract_or_null <=> dyn_cast_or_null

The target of the cast must be a subclass of Constant.

Function Documentation

◆ dyn_extract()

template<class X, class Y>

std::enable_if_t< detail::IsValidPointer< X, Y >::value, X * > llvm::mdconst::dyn_extract ( Y && MD )

inline

Extract a Value from Metadata, if any.

As an analogue to dyn_cast_or_null(), extract the Value subclass X from MD, return null if MD doesn't contain a Value or if the Value it does contain is of the wrong subclass.

Definition at line 694 of file Metadata.h.

References llvm::dyn_cast(), and Y.

Referenced by llvm::memprof::CallStackTrie::addCallStack(), llvm::buildOpSpirvDecorations(), llvm::cacheAnnotationFromMD(), computeFunctionSummary(), llvm::TargetLoweringObjectFileELF::emitModuleMetadata(), llvm::hlsl::rootsig::extractMdFloatValue(), extractMdIntValue(), llvm::hlsl::rootsig::extractMdIntValue(), llvm::extractProfTotalWeight(), llvm::getAlign(), llvm::DOTGraphTraits< DOTFuncInfo * >::getEdgeAttributes(), GetFunctionFromMDNode(), getLocCookie(), llvm::getValueProfDataFromInst(), haveCommonPrefix(), insertSpirvDecorations(), IsScalarTBAANodeImpl(), llvm::mayHaveValueProfileOfKind(), llvm::PseudoProbeManager::PseudoProbeManager(), llvm::AMDGPUPALMetadata::readFromIR(), saveFilteredNewMIBNodes(), and llvm::scaleProfData().

◆ dyn_extract_or_null()

template<class X, class Y>

std::enable_if_t< detail::IsValidPointer< X, Y >::value, X * > llvm::mdconst::dyn_extract_or_null ( Y && MD )

inline

Extract a Value from Metadata, if any, allowing null.

As an analogue to dyn_cast_or_null(), extract the Value subclass X from MD, return null if MD doesn't contain a Value or if the Value it does contain is of the wrong subclass, allowing MD to be null.

Definition at line 707 of file Metadata.h.

References llvm::dyn_cast(), llvm::dyn_cast_or_null(), and Y.

Referenced by llvm::cacheAnnotationFromMD(), llvm::getDebugMetadataVersionFromModule(), llvm::UpgradeDebugInfo(), llvm::UpgradeModuleFlags(), llvm::UpgradeNVVMAnnotations(), and llvm::TBAAVerifier::visitTBAAMetadata().