Inheritance diagram for Tofino::IXBar:

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Classes
struct	hash_matrix_reqs

struct	HashDistAllocPostExpand

struct	HashDistIRUse

struct	HashDistUse

struct	Use

Public Types
using	byte_type_t = ::IXBar::byte_type_t

using	HashDistDest_t = ::IXBar::HashDistDest_t

Public Types inherited from IXBar
enum	byte_speciality_t { NONE , ATCAM_DOUBLE , ATCAM_INDEX , RANGE_LO , RANGE_HI , BYTE_SPECIALITIES }

enum	byte_type_t { NO_BYTE_TYPE , ATCAM , PARTITION_INDEX , RANGE }

enum	HashDistDest_t { HD_IMMED_LO , HD_IMMED_HI , HD_STATS_ADR , HD_METER_ADR , HD_ACTIONDATA_ADR , HD_PRECOLOR , HD_HASHMOD , HD_DESTS }

enum	parity_status_t { PARITY_NONE , PARITY_ENABLED , PARITY_DISABLED }

Public Member Functions
bool	find_alloc (safe_vector< IXBar::Use::Byte > &alloc_use, bool ternary, safe_vector< IXBar::Use::Byte * > &alloced, hash_matrix_reqs &hm_reqs, unsigned byte_mask=~0U)

BFN::Alloc1D< std::pair< PHV::Container, int >, TofinoIXBarSpec::BYTE_GROUPS > &	get_byte_group_use ()

BFN::Alloc2Dbase< std::pair< PHV::Container, int > > &	get_exact_use ()

BFN::Alloc2Dbase< std::pair< PHV::Container, int > > &	get_ternary_use ()

unsigned	toIXBarOutputByte (bool ternary, int group, int byte)

Public Member Functions inherited from IXBar
virtual void	update (cstring name, const Use &alloc)=0

Public Member Functions inherited from P4::IHasDbPrint
void	print () const

Static Public Member Functions
static int	get_hash_single_bits ()

static int	get_meter_alu_hash_bits ()

static Use &	getUse (autoclone_ptr<::IXBar::Use > &ac)

static const Use &	getUse (const autoclone_ptr<::IXBar::Use > &ac)

Static Public Member Functions inherited from IXBar
static IXBar *	create ()

static HashDistDest_t	dest_location (const IR::Node *node, bool precolor=false)

static std::string	hash_dist_name (HashDistDest_t dest)

Static Public Attributes
static constexpr auto	ATCAM = ::IXBar::ATCAM

static constexpr auto	HD_ACTIONDATA_ADR = ::IXBar::HD_ACTIONDATA_ADR

static constexpr auto	HD_DESTS = ::IXBar::HD_DESTS

static constexpr auto	HD_HASHMOD = ::IXBar::HD_HASHMOD

static constexpr auto	HD_IMMED_HI = ::IXBar::HD_IMMED_HI

static constexpr auto	HD_IMMED_LO = ::IXBar::HD_IMMED_LO

static constexpr auto	HD_METER_ADR = ::IXBar::HD_METER_ADR

static constexpr auto	HD_PRECOLOR = ::IXBar::HD_PRECOLOR

static constexpr auto	HD_STATS_ADR = ::IXBar::HD_STATS_ADR

static constexpr auto	NO_BYTE_TYPE = ::IXBar::NO_BYTE_TYPE

static constexpr auto	PARTITION_INDEX = ::IXBar::PARTITION_INDEX

static constexpr auto	RANGE = ::IXBar::RANGE

Static Public Attributes inherited from IXBar
static constexpr int	LAMB_LINE_SELECT_BITS = 6

static constexpr int	RAM_LINE_SELECT_BITS = 10

Friends
class	IXBarRealign

Additional Inherited Members
Public Attributes inherited from IXBar
cstring	failure_reason

Protected Types inherited from IXBar
typedef std::map< Use::Byte, safe_vector< FieldInfo > >	ContByteConversion

Protected Member Functions inherited from IXBar
void	create_alloc (ContByteConversion &map_alloc, IXBar::Use &alloc)

void	create_alloc (ContByteConversion &map_alloc, safe_vector< Use::Byte > &bytes)

Static Protected Member Functions inherited from IXBar
template<class T, int S>
static void	add_names (const BFN::Alloc1D< T, S > &n, std::map< cstring, char > &names)

template<class T, int R, int C>
static void	add_names (const BFN::Alloc2D< T, R, C > &n, std::map< cstring, char > &names)

static void	add_names (const std::pair< PHV::Container, int > &c, std::map< cstring, char > &names)

template<class T>
static void	add_names (const T &n, std::map< cstring, char > &names)

static void	add_names (cstring n, std::map< cstring, char > &names)

static void	add_names (PHV::Container c, std::map< cstring, char > &names)

static void	add_use (ContByteConversion &map_alloc, const PHV::Field field, const PhvInfo &phv, const IR::MAU::Table ctxt, std::optional< cstring > aliasSourceName, const le_bitrange *bits=nullptr, int flags=0, byte_type_t byte_type=NO_BYTE_TYPE, unsigned extra_align=0, int range_index=0, int pragma_forced_ixbar_group=-1)

static void	sort_names (std::map< cstring, char > &names)

template<class T>
static void	write_group (std::ostream &out, const T &grp, std::map< cstring, char > &fields)

static void	write_one (std::ostream &out, const std::pair< cstring, int > &f, std::map< cstring, char > &fields)

static void	write_one (std::ostream &out, const std::pair< PHV::Container, int > &f, std::map< cstring, char > &fields)

static void	write_one (std::ostream &out, cstring n, std::map< cstring, char > &names)

static void	write_one (std::ostream &out, PHV::Container f, std::map< cstring, char > &fields)

Protected Attributes inherited from IXBar
ordered_map< const IR::MAU::AttachedMemory *, const IXBar::Use & >	allocated_attached

Member Function Documentation

◆ find_alloc()

bool IXBar::find_alloc	(	safe_vector< IXBar::Use::Byte > &	alloc_use,
		bool	ternary,
		safe_vector< IXBar::Use::Byte * > &	alloced,
		hash_matrix_reqs &	hm_reqs,
		unsigned	byte_mask = ~0U )

The algorithm for the allocation of bytes from the table to the input xbar, both for the TCAM and SRAM xbar. The input xbar is defined in section 6.1.8 Match Input Xbar of the uArch.

The input xbar for SRAM is 128 bytes, divided into 8 sections of 16 bytes (128 bits). As defined in section 6.2.3 Exact Match Row Vertical/Horizontal (VH) Xbars, any of the 8 sections can go to any search bus within the match array. However, a search bus can only input one of input xbar groups. Thus to minimize the width of the match, the algorithm must minimize the number of input xbar groups needed. Keep in mind that a search bus is 128 bits as well, so that only one search bus is need for an entire input xbar group.

The input xbar for TCAM is 66 bytes, divided into 6 groups of 11 bytes. These groups of 11 bytes can be thought of as a group of 5 bytes, a mid byte and a final group of 5 bytes. The reason for this odd structure is described in section 6.3.5 TCAM Matching Setup. Each TCAM is 44 bits. The lower 40 bits of the TCAM can pull from any 5 byte group, and the upper 4 bits can pull from any nibble of a midbyte.

An input xbar groups has the capability to be shared between multiple tables. Say for instance two separate ternary tables include a 40 bit field, and were to be placed in the same stage. If that 40 bit field occupied a single TCAM input xbar group, then two separate TCAMs, one for each table can pull from the same input xbar groups.

The algorithm works as follows:

Calculate the minimum number of midbytes/groups needed for a particular table
Run potentially two versions of a fitting algorithm.
- On the first iteration, prefer groups that have capabilities to share input xbar bytes.
- If, when found groups were preferred, the bytes did not fit within the alloted amount of space, prefer input xbar groups with the most open space and just try to pack.
- If neither fit, then increase the minimum amount groups/midbytes

ARGUMENTS: alloc_use vector of Byte objects that need to be allocated on the ixbar ternary true for ternary ixbar, false for exact alloced output – the Byte objects that were successfully allocated, as we want to fill out the values after we know the bytes don't break any hash constraints hm_reqs how much space, if any is required to be reserved on the hash matrix byte_mask which bytes in ixbar groups to use – default mask of ~0 means use any bytes

Classes

Public Types

Public Member Functions

Static Public Member Functions

Static Public Attributes

Friends

Additional Inherited Members

Member Function Documentation

◆ find_alloc()