#include <bridged_packing.h>

Inheritance diagram for PackWithConstraintSolver:

Public Member Functions
	PackWithConstraintSolver (const PhvInfo &p, ConstraintSolver &solver, const ordered_set< cstring > &c, ordered_map< cstring, const IR::Type_StructLike * > &r, PackingCandidateFields &pcf, PackingConstraints &pc)

void	end_apply () override

Visitor::profile_t	init_apply (const IR::Node *root) override

void	optimize ()

bool	preorder (const IR::BFN::DigestFieldList *dfl) override

bool	preorder (const IR::HeaderOrMetadata *hdr) override

void	set_pipeline_name (cstring name)

void	solve ()

Public Member Functions inherited from P4::Inspector
const IR::Node *	apply_visitor (const IR::Node , const char name=0) override

profile_t	init_apply (const IR::Node *root) override

virtual void	loop_revisit (const IR::Node *)

virtual void	postorder (const IR::Node *)

virtual bool	preorder (const IR::Node *)

virtual void	revisit (const IR::Node *)

void	revisit_visited ()

bool	visit_in_progress (const IR::Node *n) const

void	visitAgain () const override

void	visitOnce () const override

Public Member Functions inherited from P4::Visitor
virtual bool	check_global (cstring)

virtual void	clear_globals ()

virtual Visitor *	clone () const

virtual ControlFlowVisitor *	controlFlowVisitor ()

virtual void	end_apply (const IR::Node *root)

virtual void	erase_global (cstring)

template<class T >
const T *	findContext () const

template<class T >
const T *	findContext (const Context *&c) const

template<class T >
const T *	findOrigCtxt () const

template<class T >
const T *	findOrigCtxt (const Context *&c) const

virtual Visitor &	flow_clone ()

virtual void	flow_merge (Visitor &)

virtual bool	flow_merge_closure (Visitor &)

virtual void	flow_merge_global_from (cstring)

virtual void	flow_merge_global_to (cstring)

const Context *	getChildContext () const

int	getChildrenVisited () const

const Context *	getContext () const

int	getContextDepth () const

const IR::Node *	getCurrentNode () const

template<class T >
const T *	getCurrentNode () const

const IR::Node *	getOriginal () const

template<class T >
const T *	getOriginal () const

template<class T >
const T *	getParent () const

virtual bool	has_flow_joins () const

profile_t	init_apply (const IR::Node root, const Context parent_context)

bool	isInContext (const IR::Node *n) const

virtual const char *	name () const

template<class T >
void	parallel_visit (const IR::Vector< T > &v, const char *name, int cidx)

template<class T >
void	parallel_visit (const IR::Vector< T > &v, const char *name=0)

template<class T >
void	parallel_visit (IR::Vector< T > &v, const char *name, int cidx)

template<class T >
void	parallel_visit (IR::Vector< T > &v, const char *name=0)

void	print_context () const

const Visitor &	setCalledBy (const Visitor *visitor)

void	setName (const char *name)

void	visit (const IR::Node &n, const char *name, int cidx)

void	visit (const IR::Node &n, const char *name=0)

void	visit (const IR::Node &n, const char name, int cidx)

void	visit (const IR::Node &n, const char name=0)

void	visit (const IR::Node const &n, const char name, int cidx)

void	visit (const IR::Node const &n, const char name=0)

void	visit (IR::Node &n, const char *name, int cidx)

void	visit (IR::Node &n, const char *name=0)

void	visit (IR::Node &, const char =0, int=0)

template<class T , typename = std::enable_if_t<Util::has_SourceInfo_v<T> && !std::is_pointer_v<T>>, class... Args>
void	warn (const int kind, const char *format, const T &node, Args &&...args)
	The const ref variant of the above.

template<class T , typename = std::enable_if_t<Util::has_SourceInfo_v<T>>, class... Args>
void	warn (const int kind, const char format, const T node, Args &&...args)

bool	warning_enabled (int warning_kind) const

Additional Inherited Members
Public Types inherited from P4::Visitor
typedef Visitor_Context	Context

Static Public Member Functions inherited from P4::Visitor
static cstring	demangle (const char *)

static bool	warning_enabled (const Visitor *visitor, int warning_kind)

Public Attributes inherited from P4::Visitor
const Visitor *	called_by = nullptr

cstring	internalName

SplitFlowVisit_base *&	split_link

SplitFlowVisit_base *	split_link_mem = nullptr

Protected Member Functions inherited from P4::Visitor
virtual void	init_join_flows (const IR::Node *)

virtual bool	join_flows (const IR::Node *)

virtual void	post_join_flows (const IR::Node , const IR::Node )

void	visit_children (const IR::Node *, std::function< void()> fn)

Protected Attributes inherited from P4::Visitor
bool	dontForwardChildrenBeforePreorder = false

bool	joinFlows = false

bool	visitDagOnce = true

Detailed Description

The class adjusts the packing of headers/metadata/digest field lists that contain the fields with the @flexible annotation whose width is not a multiply of eight bits.

The candidates for packing adjustment can be delivered through the constructor. This approach is used for bridged headers. If the list of candidates (PackWithConstraintSolver::candidates) is empty, the inspector looks for the candidates among all headers/metadata (IR::HeaderOrMetadata) and digest field lists (IR::BFN::DigestFieldList).

The class then computes the optimal field packing using the constraint solver (PackWithConstraintSolver::solver). We modeled as a single (larger) optimization problem as opposed to multiple (smaller) optimization because a field may exists in multiple flexible field lists. The computed alignment for the field must be consistent across all instances of the flexible field list. However, the optimizer is still optimizing each field list with individual optimization goals and constraints. The number of constraints scales linearly with respect to the number of fields list instances. Within each field lists, the number of constraints scales at O(n^2) with respect to the number of fields.

Logging options
-Tbridged_packing:1	A list of @flexible fields whose width is not a multiple of eight bits Original (non-@flexible) and adjusted (@flexible whose width in not a multiply of eight bits) fields being used in the adjusted headers/metadata/digest field lists Adjusted headers/metadata/digest field lists
-Tbridged_packing:3	Which digest field list is being processed
-Tbridged_packing:5	Print candidates to pack and when a header/metadata/digest field list is skipped

Precondition: Up-to-date PhvInfo.

Member Function Documentation

◆ end_apply()

void PackWithConstraintSolver::end_apply ( )

overridevirtual

Runs optimizer to trigger adding constraints to the constraint solver.

Reimplemented from P4::Visitor.

◆ optimize()

void PackWithConstraintSolver::optimize ( )

Triggers adding constraints for all @flexible fields whose width is not a multiply of eight bits to the constraint solver.

There are two steps. The first one adds constraints for individual headers/metadata/digest field lists using ConstraintSolver::add_constraints. The other step adds mutually aligned constraints for fields of all headers/metadata/digest field lists using ConstraintSolver::add_mutually_aligned_constraints.

If corresponding logging is enabled, the Z3 solver assertions are printed out to the log.

See also: ConstraintSolver for logging options to log the Z3 solver assertions.

◆ preorder() [1/2]

bool PackWithConstraintSolver::preorder ( const IR::BFN::DigestFieldList * d )

override

Looks for @flexible fields of digest field lists whose with is, and is not a multiple of eight bits and updates the PackWithConstraintSolver::byteAlignedFieldsMap, and PackWithConstraintSolver::nonByteAlignedFieldsMap maps, respectively.

Also stores the mapping from a PHV::Field to the corresponding IR::StructField into the PackWithConstraintSolver::phvFieldToStructFieldMap map and the mapping from a header/metadata name to the corresponding IR::Type_StructLike into the PackWithConstraintSolver::headerMap map.

◆ preorder() [2/2]

bool PackWithConstraintSolver::preorder ( const IR::HeaderOrMetadata * hdr )

override

Looks for @flexible header/metadata fields. For those whose witdh is a multiple of eight bits, it updates the PackWithConstraintSolver::byteAlignedFieldsMap map. For those whose width is not a multiple of eight bits, it updates the PackWithConstraintSolver::nonByteAlignedFieldsMap map.

Also stores the mapping from a PHV::Field to the corresponding IR::StructField into the PackWithConstraintSolver::phvFieldToStructFieldMap map and the mapping from a header/metadata name to the corresponding IR::Type_StructLike into the PackWithConstraintSolver::headerMap map.

◆ solve()

void PackWithConstraintSolver::solve ( )

Runs the constraint solver to get adjusted packing of @flexible fields whose width is not a multiply of eight bits and creates adjusted headers/metadata/digest field lists containing these fields.

Adjusted header/metadata/digest field list is composed as follows:

Original non-@flexbile and non-@padding fields
Original @flexible fields whose width is a multiply of eight bits
Adjusted @flexible fields whose width is not a multiply of eigth bits including possible padding fields obtained from the constraint solver. The padding fields are annotated with @padding and @overlayable.

Adjusted headers/metadata/digest field lists are stored in PackWithConstraintSolver::repackedTypes.

Public Member Functions