1 //===-- llvm/Target/TargetInstrItineraries.h - Scheduling -------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file describes the structures used for instruction itineraries and
11 // stages. This is used by schedulers to determine instruction stages and
14 //===----------------------------------------------------------------------===//
16 #ifndef LLVM_TARGET_TARGETINSTRITINERARIES_H
17 #define LLVM_TARGET_TARGETINSTRITINERARIES_H
23 //===----------------------------------------------------------------------===//
24 /// Instruction stage - These values represent a non-pipelined step in
25 /// the execution of an instruction. Cycles represents the number of
26 /// discrete time slots needed to complete the stage. Units represent
27 /// the choice of functional units that can be used to complete the
28 /// stage. Eg. IntUnit1, IntUnit2. NextCycles indicates how many
29 /// cycles should elapse from the start of this stage to the start of
30 /// the next stage in the itinerary. A value of -1 indicates that the
31 /// next stage should start immediately after the current one.
35 /// indicates that the stage occupies FU x for 1 cycle and that
36 /// the next stage starts immediately after this one.
39 /// indicates that the stage occupies either FU x or FU y for 2
40 /// consecuative cycles and that the next stage starts one cycle
41 /// after this stage starts. That is, the stage requirements
45 /// indicates that the stage occupies FU x for 1 cycle and that
46 /// the next stage starts in this same cycle. This can be used to
47 /// indicate that the instruction requires multiple stages at the
51 unsigned Cycles_; ///< Length of stage in machine cycles
52 unsigned Units_; ///< Choice of functional units
53 int NextCycles_; ///< Number of machine cycles to next stage
55 /// getCycles - returns the number of cycles the stage is occupied
56 unsigned getCycles() const {
60 /// getUnits - returns the choice of FUs
61 unsigned getUnits() const {
65 /// getNextCycles - returns the number of cycles from the start of
66 /// this stage to the start of the next stage in the itinerary
67 unsigned getNextCycles() const {
68 return (NextCycles_ >= 0) ? (unsigned)NextCycles_ : Cycles_;
73 //===----------------------------------------------------------------------===//
74 /// Instruction itinerary - An itinerary represents a sequential series of steps
75 /// required to complete an instruction. Itineraries are represented as
76 /// sequences of instruction stages.
78 struct InstrItinerary {
79 unsigned First; ///< Index of first stage in itinerary
80 unsigned Last; ///< Index of last + 1 stage in itinerary
85 //===----------------------------------------------------------------------===//
86 /// Instruction itinerary Data - Itinerary data supplied by a subtarget to be
89 struct InstrItineraryData {
90 const InstrStage *Stages; ///< Array of stages selected
91 const InstrItinerary *Itineratries; ///< Array of itineraries selected
95 InstrItineraryData() : Stages(0), Itineratries(0) {}
96 InstrItineraryData(const InstrStage *S, const InstrItinerary *I)
97 : Stages(S), Itineratries(I) {}
99 /// isEmpty - Returns true if there are no itineraries.
101 bool isEmpty() const { return Itineratries == 0; }
103 /// begin - Return the first stage of the itinerary.
105 const InstrStage *begin(unsigned ItinClassIndx) const {
106 unsigned StageIdx = Itineratries[ItinClassIndx].First;
107 return Stages + StageIdx;
110 /// end - Return the last+1 stage of the itinerary.
112 const InstrStage *end(unsigned ItinClassIndx) const {
113 unsigned StageIdx = Itineratries[ItinClassIndx].Last;
114 return Stages + StageIdx;
117 /// getLatency - Return the scheduling latency of the given class. A
118 /// simple latency value for an instruction is an over-simplification
119 /// for some architectures, but it's a reasonable first approximation.
121 unsigned getLatency(unsigned ItinClassIndx) const {
122 // If the target doesn't provide latency information, use a simple
123 // non-zero default value for all instructions.
127 // Caclulate the maximum completion time for any stage. The
128 // assumption is that all inputs are consumed at the start of the
129 // first stage and that all outputs are produced at the end of the
130 // latest completing last stage.
131 unsigned Latency = 0, StartCycle = 0;
132 for (const InstrStage *IS = begin(ItinClassIndx), *E = end(ItinClassIndx);
134 Latency = std::max(Latency, StartCycle + IS->getCycles());
135 StartCycle += IS->getNextCycles();
143 } // End llvm namespace