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[MachineTraceMetrics] Add computeDepth function (NFCI). 

Summary:
This function is used in D36619 to update the instruction depths
incrementally.

Reviewers: efriedma, Gerolf, MatzeB, fhahn

Reviewed By: fhahn

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D36696

llvm-svn: 312714
This commit is contained in:
Florian Hahn 2017-09-07 11:51:30 +00:00
parent c09d5611c4
commit cf0cdd4c02
2 changed files with 69 additions and 54 deletions
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23
llvm/include/llvm/CodeGen/MachineTraceMetrics.h
View File

@ -47,6 +47,7 @@
#ifndef LLVM_CODEGEN_MACHINETRACEMETRICS_H
#define LLVM_CODEGEN_MACHINETRACEMETRICS_H
#include "llvm/ADT/SparseSet.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/None.h"
@ -68,6 +69,22 @@ class raw_ostream;
class TargetInstrInfo;
class TargetRegisterInfo;
// Keep track of physreg data dependencies by recording each live register unit.
// Associate each regunit with an instruction operand. Depending on the
// direction instructions are scanned, it could be the operand that defined the
// regunit, or the highest operand to read the regunit.
struct LiveRegUnit {
unsigned RegUnit;
unsigned Cycle = 0;
const MachineInstr *MI = nullptr;
unsigned Op = 0;
unsigned getSparseSetIndex() const { return RegUnit; }
LiveRegUnit(unsigned RU) : RegUnit(RU) {}
};
class MachineTraceMetrics : public MachineFunctionPass {
const MachineFunction *MF = nullptr;
const TargetInstrInfo *TII = nullptr;
@ -343,6 +360,12 @@ public:
/// Get the trace that passes through MBB.
/// The trace is computed on demand.
Trace getTrace(const MachineBasicBlock *MBB);
/// Updates the depth of an machine instruction, given RegUnits.
void updateDepth(TraceBlockInfo &TBI, const MachineInstr&,
SparseSet<LiveRegUnit> &RegUnits);
void updateDepth(const MachineBasicBlock *, const MachineInstr&,
SparseSet<LiveRegUnit> &RegUnits);
};
/// Strategies for selecting traces.

100
llvm/lib/CodeGen/MachineTraceMetrics.cpp
View File

@ -694,25 +694,6 @@ static void getPHIDeps(const MachineInstr &UseMI,
}
}
// Keep track of physreg data dependencies by recording each live register unit.
// Associate each regunit with an instruction operand. Depending on the
// direction instructions are scanned, it could be the operand that defined the
// regunit, or the highest operand to read the regunit.
namespace {
struct LiveRegUnit {
unsigned RegUnit;
unsigned Cycle = 0;
const MachineInstr *MI = nullptr;
unsigned Op = 0;
unsigned getSparseSetIndex() const { return RegUnit; }
LiveRegUnit(unsigned RU) : RegUnit(RU) {}
};
} // end anonymous namespace
// Identify physreg dependencies for UseMI, and update the live regunit
// tracking set when scanning instructions downwards.
static void updatePhysDepsDownwards(const MachineInstr *UseMI,
@ -797,6 +778,51 @@ computeCrossBlockCriticalPath(const TraceBlockInfo &TBI) {
return MaxLen;
}
void MachineTraceMetrics::Ensemble::
updateDepth(MachineTraceMetrics::TraceBlockInfo &TBI, const MachineInstr &UseMI,
SparseSet<LiveRegUnit> &RegUnits) {
SmallVector<DataDep, 8> Deps;
// Collect all data dependencies.
if (UseMI.isPHI())
getPHIDeps(UseMI, Deps, TBI.Pred, MTM.MRI);
else if (getDataDeps(UseMI, Deps, MTM.MRI))
updatePhysDepsDownwards(&UseMI, Deps, RegUnits, MTM.TRI);
// Filter and process dependencies, computing the earliest issue cycle.
unsigned Cycle = 0;
for (const DataDep &Dep : Deps) {
const TraceBlockInfo&DepTBI =
BlockInfo[Dep.DefMI->getParent()->getNumber()];
// Ignore dependencies from outside the current trace.
if (!DepTBI.isUsefulDominator(TBI))
continue;
assert(DepTBI.HasValidInstrDepths && "Inconsistent dependency");
unsigned DepCycle = Cycles.lookup(Dep.DefMI).Depth;
// Add latency if DefMI is a real instruction. Transients get latency 0.
if (!Dep.DefMI->isTransient())
DepCycle += MTM.SchedModel
.computeOperandLatency(Dep.DefMI, Dep.DefOp, &UseMI, Dep.UseOp);
Cycle = std::max(Cycle, DepCycle);
}
// Remember the instruction depth.
InstrCycles &MICycles = Cycles[&UseMI];
MICycles.Depth = Cycle;
if (TBI.HasValidInstrHeights) {
// Update critical path length.
TBI.CriticalPath = std::max(TBI.CriticalPath, Cycle + MICycles.Height);
DEBUG(dbgs() << TBI.CriticalPath << '\t' << Cycle << '\t' << UseMI);
} else {
DEBUG(dbgs() << Cycle << '\t' << UseMI);
}
}
void MachineTraceMetrics::Ensemble::
updateDepth(const MachineBasicBlock *MBB, const MachineInstr &UseMI,
SparseSet<LiveRegUnit> &RegUnits) {
updateDepth(BlockInfo[MBB->getNumber()], UseMI, RegUnits);
}
/// Compute instruction depths for all instructions above or in MBB in its
/// trace. This assumes that the trace through MBB has already been computed.
void MachineTraceMetrics::Ensemble::
@ -822,7 +848,6 @@ computeInstrDepths(const MachineBasicBlock *MBB) {
RegUnits.setUniverse(MTM.TRI->getNumRegUnits());
// Go through trace blocks in top-down order, stopping after the center block.
SmallVector<DataDep, 8> Deps;
while (!Stack.empty()) {
MBB = Stack.pop_back_val();
DEBUG(dbgs() << "\nDepths for BB#" << MBB->getNumber() << ":\n");
@ -848,40 +873,7 @@ computeInstrDepths(const MachineBasicBlock *MBB) {
TBI.CriticalPath = computeCrossBlockCriticalPath(TBI);
for (const auto &UseMI : *MBB) {
// Collect all data dependencies.
Deps.clear();
if (UseMI.isPHI())
getPHIDeps(UseMI, Deps, TBI.Pred, MTM.MRI);
else if (getDataDeps(UseMI, Deps, MTM.MRI))
updatePhysDepsDownwards(&UseMI, Deps, RegUnits, MTM.TRI);
// Filter and process dependencies, computing the earliest issue cycle.
unsigned Cycle = 0;
for (const DataDep &Dep : Deps) {
const TraceBlockInfo&DepTBI =
BlockInfo[Dep.DefMI->getParent()->getNumber()];
// Ignore dependencies from outside the current trace.
if (!DepTBI.isUsefulDominator(TBI))
continue;
assert(DepTBI.HasValidInstrDepths && "Inconsistent dependency");
unsigned DepCycle = Cycles.lookup(Dep.DefMI).Depth;
// Add latency if DefMI is a real instruction. Transients get latency 0.
if (!Dep.DefMI->isTransient())
DepCycle += MTM.SchedModel
.computeOperandLatency(Dep.DefMI, Dep.DefOp, &UseMI, Dep.UseOp);
Cycle = std::max(Cycle, DepCycle);
}
// Remember the instruction depth.
InstrCycles &MICycles = Cycles[&UseMI];
MICycles.Depth = Cycle;
if (!TBI.HasValidInstrHeights) {
DEBUG(dbgs() << Cycle << '\t' << UseMI);
continue;
}
// Update critical path length.
TBI.CriticalPath = std::max(TBI.CriticalPath, Cycle + MICycles.Height);
DEBUG(dbgs() << TBI.CriticalPath << '\t' << Cycle << '\t' << UseMI);
updateDepth(TBI, UseMI, RegUnits);
}
}
}