X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=include%2Fllvm%2FTarget%2FTargetSchedule.td;h=0ac2eed9d56b07b339a496f523e2638c55c0e603;hb=b86a0cdb674549d8493043331cecd9cbf53b80da;hp=1b160202de47fb8fb03f06851ac3e44de732fdb5;hpb=8fa5319504d6990162fe9a3e35880e19282a3f81;p=oota-llvm.git diff --git a/include/llvm/Target/TargetSchedule.td b/include/llvm/Target/TargetSchedule.td index 1b160202de4..0ac2eed9d56 100644 --- a/include/llvm/Target/TargetSchedule.td +++ b/include/llvm/Target/TargetSchedule.td @@ -10,25 +10,80 @@ // This file defines the target-independent scheduling interfaces which should // be implemented by each target which is using TableGen based scheduling. // +// The SchedMachineModel is defined by subtargets for three categories of data: +// 1. Basic properties for coarse grained instruction cost model. +// 2. Scheduler Read/Write resources for simple per-opcode cost model. +// 3. Instruction itineraties for detailed reservation tables. +// +// (1) Basic properties are defined by the SchedMachineModel +// class. Target hooks allow subtargets to associate opcodes with +// those properties. +// +// (2) A per-operand machine model can be implemented in any +// combination of the following ways: +// +// A. Associate per-operand SchedReadWrite types with Instructions by +// modifying the Instruction definition to inherit from Sched. For +// each subtarget, define WriteRes and ReadAdvance to associate +// processor resources and latency with each SchedReadWrite type. +// +// B. In each instruction definition, name an ItineraryClass. For each +// subtarget, define ItinRW entries to map ItineraryClass to +// per-operand SchedReadWrite types. Unlike method A, these types may +// be subtarget specific and can be directly associated with resources +// by defining SchedWriteRes and SchedReadAdvance. +// +// C. In the subtarget, map SchedReadWrite types to specific +// opcodes. This overrides any SchedReadWrite types or +// ItineraryClasses defined by the Instruction. As in method B, the +// subtarget can directly associate resources with SchedReadWrite +// types by defining SchedWriteRes and SchedReadAdvance. +// +// D. In either the target or subtarget, define SchedWriteVariant or +// SchedReadVariant to map one SchedReadWrite type onto another +// sequence of SchedReadWrite types. This allows dynamic selection of +// an instruction's machine model via custom C++ code. It also allows +// a machine-independent SchedReadWrite type to map to a sequence of +// machine-dependent types. +// +// (3) A per-pipeline-stage machine model can be implemented by providing +// Itineraries in addition to mapping instructions to ItineraryClasses. //===----------------------------------------------------------------------===// +// Include legacy support for instruction itineraries. include "llvm/Target/TargetItinerary.td" -// The SchedMachineModel is defined by subtargets for three categories of data: -// 1) Basic properties for coarse grained instruction cost model. -// 2) Scheduler Read/Write resources for simple per-opcode cost model. -// 3) Instruction itineraties for detailed reservation tables. +class Instruction; // Forward def + +// DAG operator that interprets the DAG args as Instruction defs. +def instrs; + +// DAG operator that interprets each DAG arg as a regex pattern for +// matching Instruction opcode names. +// The regex must match the beginning of the opcode (as in Python re.match). +// To avoid matching prefixes, append '$' to the pattern. +def instregex; + +// Define the SchedMachineModel and provide basic properties for +// coarse grained instruction cost model. Default values for the +// properties are defined in MCSchedModel. A value of "-1" in the +// target description's SchedMachineModel indicates that the property +// is not overriden by the target. // -// Default values for basic properties are defined in MCSchedModel. "-1" -// indicates that the property is not overriden by the target description. +// Target hooks allow subtargets to associate LoadLatency and +// HighLatency with groups of opcodes. +// +// See MCSchedule.h for detailed comments. class SchedMachineModel { int IssueWidth = -1; // Max micro-ops that may be scheduled per cycle. int MinLatency = -1; // Determines which instrucions are allowed in a group. // (-1) inorder (0) ooo, (1): inorder +var latencies. + int MicroOpBufferSize = -1; // Max micro-ops that can be buffered. int LoadLatency = -1; // Cycles for loads to access the cache. int HighLatency = -1; // Approximation of cycles for "high latency" ops. int MispredictPenalty = -1; // Extra cycles for a mispredicted branch. + // Per-cycle resources tables. ProcessorItineraries Itineraries = NoItineraries; bit NoModel = 0; // Special tag to indicate missing machine model. @@ -38,4 +93,281 @@ def NoSchedModel : SchedMachineModel { let NoModel = 1; } -// TODO: Define classes for processor and scheduler resources. +// Define a kind of processor resource that may be common across +// similar subtargets. +class ProcResourceKind; + +// Define a number of interchangeable processor resources. NumUnits +// determines the throughput of instructions that require the resource. +// +// An optional Super resource may be given to model these resources as +// a subset of the more general super resources. Using one of these +// resources implies using one of the super resoruces. +// +// ProcResourceUnits normally model a few buffered resources within an +// out-of-order engine that the compiler attempts to conserve. +// Buffered resources may be held for multiple clock cycles, but the +// scheduler does not pin them to a particular clock cycle relative to +// instruction dispatch. Setting BufferSize=0 changes this to an +// in-order resource. In this case, the scheduler counts down from the +// cycle that the instruction issues in-order, forcing an interlock +// with subsequent instructions that require the same resource until +// the number of ResourceCyles specified in WriteRes expire. +// +// SchedModel ties these units to a processor for any stand-alone defs +// of this class. Instances of subclass ProcResource will be automatically +// attached to a processor, so SchedModel is not needed. +class ProcResourceUnits { + ProcResourceKind Kind = kind; + int NumUnits = num; + ProcResourceKind Super = ?; + int BufferSize = -1; + SchedMachineModel SchedModel = ?; +} + +// EponymousProcResourceKind helps implement ProcResourceUnits by +// allowing a ProcResourceUnits definition to reference itself. It +// should not be referenced anywhere else. +def EponymousProcResourceKind : ProcResourceKind; + +// Subtargets typically define processor resource kind and number of +// units in one place. +class ProcResource : ProcResourceKind, + ProcResourceUnits; + +class ProcResGroup resources> : ProcResourceKind { + list Resources = resources; + SchedMachineModel SchedModel = ?; +} + +// A target architecture may define SchedReadWrite types and associate +// them with instruction operands. +class SchedReadWrite; + +// List the per-operand types that map to the machine model of an +// instruction. One SchedWrite type must be listed for each explicit +// def operand in order. Additional SchedWrite types may optionally be +// listed for implicit def operands. SchedRead types may optionally +// be listed for use operands in order. The order of defs relative to +// uses is insignificant. This way, the same SchedReadWrite list may +// be used for multiple forms of an operation. For example, a +// two-address instruction could have two tied operands or single +// operand that both reads and writes a reg. In both cases we have a +// single SchedWrite and single SchedRead in any order. +class Sched schedrw> { + list SchedRW = schedrw; +} + +// Define a scheduler resource associated with a def operand. +class SchedWrite : SchedReadWrite; +def NoWrite : SchedWrite; + +// Define a scheduler resource associated with a use operand. +class SchedRead : SchedReadWrite; + +// Define a SchedWrite that is modeled as a sequence of other +// SchedWrites with additive latency. This allows a single operand to +// be mapped the resources composed from a set of previously defined +// SchedWrites. +// +// If the final write in this sequence is a SchedWriteVariant marked +// Variadic, then the list of prior writes are distributed across all +// operands after resolving the predicate for the final write. +// +// SchedModel silences warnings but is ignored. +class WriteSequence writes, int rep = 1> : SchedWrite { + list Writes = writes; + int Repeat = rep; + SchedMachineModel SchedModel = ?; +} + +// Define values common to WriteRes and SchedWriteRes. +// +// SchedModel ties these resources to a processor. +class ProcWriteResources resources> { + list ProcResources = resources; + list ResourceCycles = []; + int Latency = 1; + int NumMicroOps = 1; + bit BeginGroup = 0; + bit EndGroup = 0; + // Allow a processor to mark some scheduling classes as unsupported + // for stronger verification. + bit Unsupported = 0; + SchedMachineModel SchedModel = ?; +} + +// Define the resources and latency of a SchedWrite. This will be used +// directly by targets that have no itinerary classes. In this case, +// SchedWrite is defined by the target, while WriteResources is +// defined by the subtarget, and maps the SchedWrite to processor +// resources. +// +// If a target already has itinerary classes, SchedWriteResources can +// be used instead to define subtarget specific SchedWrites and map +// them to processor resources in one place. Then ItinRW can map +// itinerary classes to the subtarget's SchedWrites. +// +// ProcResources indicates the set of resources consumed by the write. +// Optionally, ResourceCycles indicates the number of cycles the +// resource is consumed. Each ResourceCycles item is paired with the +// ProcResource item at the same position in its list. Since +// ResourceCycles are rarely specialized, the list may be +// incomplete. By default, resources are consumed for a single cycle, +// regardless of latency, which models a fully pipelined processing +// unit. A value of 0 for ResourceCycles means that the resource must +// be available but is not consumed, which is only relevant for +// unbuffered resources. +// +// By default, each SchedWrite takes one micro-op, which is counted +// against the processor's IssueWidth limit. If an instruction can +// write multiple registers with a single micro-op, the subtarget +// should define one of the writes to be zero micro-ops. If a +// subtarget requires multiple micro-ops to write a single result, it +// should either override the write's NumMicroOps to be greater than 1 +// or require additional writes. Extra writes can be required either +// by defining a WriteSequence, or simply listing extra writes in the +// instruction's list of writers beyond the number of "def" +// operands. The scheduler assumes that all micro-ops must be +// dispatched in the same cycle. These micro-ops may be required to +// begin or end the current dispatch group. +class WriteRes resources> + : ProcWriteResources { + SchedWrite WriteType = write; +} + +// Directly name a set of WriteResources defining a new SchedWrite +// type at the same time. This class is unaware of its SchedModel so +// must be referenced by InstRW or ItinRW. +class SchedWriteRes resources> : SchedWrite, + ProcWriteResources; + +// Define values common to ReadAdvance and SchedReadAdvance. +// +// SchedModel ties these resources to a processor. +class ProcReadAdvance writes = []> { + int Cycles = cycles; + list ValidWrites = writes; + // Allow a processor to mark some scheduling classes as unsupported + // for stronger verification. + bit Unsupported = 0; + SchedMachineModel SchedModel = ?; +} + +// A processor may define a ReadAdvance associated with a SchedRead +// to reduce latency of a prior write by N cycles. A negative advance +// effectively increases latency, which may be used for cross-domain +// stalls. +// +// A ReadAdvance may be associated with a list of SchedWrites +// to implement pipeline bypass. The Writes list may be empty to +// indicate operands that are always read this number of Cycles later +// than a normal register read, allowing the read's parent instruction +// to issue earlier relative to the writer. +class ReadAdvance writes = []> + : ProcReadAdvance { + SchedRead ReadType = read; +} + +// Directly associate a new SchedRead type with a delay and optional +// pipeline bypess. For use with InstRW or ItinRW. +class SchedReadAdvance writes = []> : SchedRead, + ProcReadAdvance; + +// Define SchedRead defaults. Reads seldom need special treatment. +def ReadDefault : SchedRead; +def NoReadAdvance : SchedReadAdvance<0>; + +// Define shared code that will be in the same scope as all +// SchedPredicates. Available variables are: +// (const MachineInstr *MI, const TargetSchedModel *SchedModel) +class PredicateProlog { + code Code = c; +} + +// Define a predicate to determine which SchedVariant applies to a +// particular MachineInstr. The code snippet is used as an +// if-statement's expression. Available variables are MI, SchedModel, +// and anything defined in a PredicateProlog. +// +// SchedModel silences warnings but is ignored. +class SchedPredicate { + SchedMachineModel SchedModel = ?; + code Predicate = pred; +} +def NoSchedPred : SchedPredicate<[{true}]>; + +// Associate a predicate with a list of SchedReadWrites. By default, +// the selected SchedReadWrites are still associated with a single +// operand and assumed to execute sequentially with additive +// latency. However, if the parent SchedWriteVariant or +// SchedReadVariant is marked "Variadic", then each Selected +// SchedReadWrite is mapped in place to the instruction's variadic +// operands. In this case, latency is not additive. If the current Variant +// is already part of a Sequence, then that entire chain leading up to +// the Variant is distributed over the variadic operands. +class SchedVar selected> { + SchedPredicate Predicate = pred; + list Selected = selected; +} + +// SchedModel silences warnings but is ignored. +class SchedVariant variants> { + list Variants = variants; + bit Variadic = 0; + SchedMachineModel SchedModel = ?; +} + +// A SchedWriteVariant is a single SchedWrite type that maps to a list +// of SchedWrite types under the conditions defined by its predicates. +// +// A Variadic write is expanded to cover multiple "def" operands. The +// SchedVariant's Expansion list is then interpreted as one write +// per-operand instead of the usual sequential writes feeding a single +// operand. +class SchedWriteVariant variants> : SchedWrite, + SchedVariant { +} + +// A SchedReadVariant is a single SchedRead type that maps to a list +// of SchedRead types under the conditions defined by its predicates. +// +// A Variadic write is expanded to cover multiple "readsReg" operands as +// explained above. +class SchedReadVariant variants> : SchedRead, + SchedVariant { +} + +// Map a set of opcodes to a list of SchedReadWrite types. This allows +// the subtarget to easily override specific operations. +// +// SchedModel ties this opcode mapping to a processor. +class InstRW rw, dag instrlist> { + list OperandReadWrites = rw; + dag Instrs = instrlist; + SchedMachineModel SchedModel = ?; +} + +// Map a set of itinerary classes to SchedReadWrite resources. This is +// used to bootstrap a target (e.g. ARM) when itineraries already +// exist and changing InstrInfo is undesirable. +// +// SchedModel ties this ItineraryClass mapping to a processor. +class ItinRW rw, list iic> { + list MatchedItinClasses = iic; + list OperandReadWrites = rw; + SchedMachineModel SchedModel = ?; +} + +// Alias a target-defined SchedReadWrite to a processor specific +// SchedReadWrite. This allows a subtarget to easily map a +// SchedReadWrite type onto a WriteSequence, SchedWriteVariant, or +// SchedReadVariant. +// +// SchedModel will usually be provided by surrounding let statement +// and ties this SchedAlias mapping to a processor. +class SchedAlias { + SchedReadWrite MatchRW = match; + SchedReadWrite AliasRW = alias; + SchedMachineModel SchedModel = ?; +}