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Comments about operand cycles and pipeline forwarding pathes.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@115214 91177308-0d34-0410-b5e6-96231b3b80d8
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Evan Cheng 2010-09-30 22:01:50 +00:00
parent c6877b4ee1
commit a56927e3ff
1 changed files with 17 additions and 1 deletions
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18
include/llvm/Target/TargetSchedule.td
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@ -27,7 +27,6 @@ class FuncUnit;
// pipeline bypasses which can be used to forward results of instructions // pipeline bypasses which can be used to forward results of instructions
// that are forwarded to uses. // that are forwarded to uses.
class Bypass; class Bypass;
def NoBypass : Bypass; def NoBypass : Bypass;
class ReservationKind<bits<1> val> { class ReservationKind<bits<1> val> {
@ -88,6 +87,23 @@ def NoItinerary : InstrItinClass;
// Instruction itinerary data - These values provide a runtime map of an // Instruction itinerary data - These values provide a runtime map of an
// instruction itinerary class (name) to its itinerary data. // instruction itinerary class (name) to its itinerary data.
// //
// OperandCycles are optional "cycle counts". They specify the cycle after
// instruction issue the values which correspond to specific operand indices
// are defined or read. Bypasses are optional "pipeline forwarding pathes", if
// a def by an instruction is available on a specific bypass and the use can
// read from the same bypass, then the operand use latency is reduced by one.
//
// InstrItinData<IIC_iLoad_i , [InstrStage<1, [A9_Pipe1]>,
// InstrStage<1, [A9_AGU]>],
// [3, 1], [A9_LdBypass]>,
// InstrItinData<IIC_iMVNr , [InstrStage<1, [A9_Pipe0, A9_Pipe1]>],
// [1, 1], [NoBypass, A9_LdBypass]>,
//
// In this example, the instruction of IIC_iLoadi reads its input on cycle 1
// (after issue) and the result of the load is available on cycle 3. The result
// is available via forwarding path A9_LdBypass. If it's used by the first
// source operand of instructions of IIC_iMVNr class, then the operand latency
// is reduced by 1.
class InstrItinData<InstrItinClass Class, list<InstrStage> stages, class InstrItinData<InstrItinClass Class, list<InstrStage> stages,
list<int> operandcycles = [], list<int> operandcycles = [],
list<Bypass> bypasses = []> { list<Bypass> bypasses = []> {