llvm::mdconst Namespace Reference

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));

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));

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));

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.

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.

extract() [1/2]

template<class X , class Y >

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

inline

Extract a Value from Metadata.

As an analogue to cast(), extract the Value subclass X from MD.

Definition at line 666 of file Metadata.h.

extract() [2/2]

template<class X , class Y >

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

inline

Definition at line 671 of file Metadata.h.

References extract.

extract_or_null()

template<class X , class Y >

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

inline

Extract a Value from Metadata, allowing null.

As an analogue to cast_or_null(), extract the Value subclass X from MD, allowing MD to be null.

Definition at line 681 of file Metadata.h.

hasa() [1/2]

template<class X , class Y >

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

inline

Check whether Metadata has a Value.

As an analogue to isa(), check whether MD has an Value inside of type X.

Definition at line 649 of file Metadata.h.

References assert().

Referenced by hasa().

hasa() [2/2]

template<class X , class Y >

std::enable_if_t< detail::IsValidReference< X, Y & >::value, bool > llvm::mdconst::hasa ( Y &  MD )

inline

Definition at line 657 of file Metadata.h.

References hasa().