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[RegBankSelect] Improve the output of the debug messages. 

Add more information about mapping cost and chosen solution.

llvm-svn: 291629
This commit is contained in:
Quentin Colombet 2017-01-11 00:48:41 +00:00
parent 7f41c4d802
commit 0b63b31b2e
2 changed files with 46 additions and 7 deletions
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14
llvm/include/llvm/CodeGen/GlobalISel/RegBankSelect.h
View File

@ -76,6 +76,7 @@ class MachineBlockFrequencyInfo;
class MachineRegisterInfo;
class TargetPassConfig;
class TargetRegisterInfo;
class raw_ostream;
/// This pass implements the reg bank selector pass used in the GlobalISel
/// pipeline. At the end of this pass, all register operands have been assigned
@ -450,6 +451,18 @@ private:
bool operator>(const MappingCost &Cost) const {
return *this != Cost && Cost < *this;
}
/// Print this on dbgs() stream.
void dump() const;
/// Print this on \p OS;
void print(raw_ostream &OS) const;
/// Overload the stream operator for easy debug printing.
friend raw_ostream &operator<<(raw_ostream &OS, const MappingCost &Cost) {
Cost.print(OS);
return OS;
}
};
/// Interface to the target lowering info related
@ -626,6 +639,7 @@ public:
/// \endcode
bool runOnMachineFunction(MachineFunction &MF) override;
};
} // End namespace llvm.
#endif

39
llvm/lib/CodeGen/GlobalISel/RegBankSelect.cpp
View File

@ -223,6 +223,7 @@ RegisterBankInfo::InstructionMapping &RegBankSelect::findBestMapping(
for (RegisterBankInfo::InstructionMapping &CurMapping : PossibleMappings) {
MappingCost CurCost = computeMapping(MI, CurMapping, LocalRepairPts, &Cost);
if (CurCost < Cost) {
DEBUG(dbgs() << "New best: " << CurCost << '\n');
Cost = CurCost;
BestMapping = &CurMapping;
RepairPts.clear();
@ -377,8 +378,10 @@ RegBankSelect::MappingCost RegBankSelect::computeMapping(
DEBUG(dbgs() << "Evaluating mapping cost for: " << MI);
DEBUG(dbgs() << "With: " << InstrMapping << '\n');
RepairPts.clear();
if (BestCost && Cost > *BestCost)
if (BestCost && Cost > *BestCost) {
DEBUG(dbgs() << "Mapping is too expensive from the start\n");
return Cost;
}
// Moreover, to realize this mapping, the register bank of each operand must
// match this mapping. In other words, we may need to locally reassign the
@ -392,17 +395,17 @@ RegBankSelect::MappingCost RegBankSelect::computeMapping(
unsigned Reg = MO.getReg();
if (!Reg)
continue;
DEBUG(dbgs() << "Opd" << OpIdx);
DEBUG(dbgs() << "Opd" << OpIdx << '\n');
const RegisterBankInfo::ValueMapping &ValMapping =
InstrMapping.getOperandMapping(OpIdx);
// If Reg is already properly mapped, this is free.
bool Assign;
if (assignmentMatch(Reg, ValMapping, Assign)) {
DEBUG(dbgs() << " is free (match).\n");
DEBUG(dbgs() << "=> is free (match).\n");
continue;
}
if (Assign) {
DEBUG(dbgs() << " is free (simple assignment).\n");
DEBUG(dbgs() << "=> is free (simple assignment).\n");
RepairPts.emplace_back(RepairingPlacement(MI, OpIdx, *TRI, *this,
RepairingPlacement::Reassign));
continue;
@ -420,8 +423,10 @@ RegBankSelect::MappingCost RegBankSelect::computeMapping(
tryAvoidingSplit(RepairPt, MO, ValMapping);
// Check that the materialization of the repairing is possible.
if (!RepairPt.canMaterialize())
if (!RepairPt.canMaterialize()) {
DEBUG(dbgs() << "Mapping involves impossible repairing\n");
return MappingCost::ImpossibleCost();
}
// Account for the split cost and repair cost.
// Unless the cost is already saturated or we do not care about the cost.
@ -476,8 +481,10 @@ RegBankSelect::MappingCost RegBankSelect::computeMapping(
// Stop looking into what it takes to repair, this is already
// too expensive.
if (BestCost && Cost > *BestCost)
if (BestCost && Cost > *BestCost) {
DEBUG(dbgs() << "Mapping is too expensive, stop processing\n");
return Cost;
}
// No need to accumulate more cost information.
// We need to still gather the repairing information though.
@ -485,6 +492,7 @@ RegBankSelect::MappingCost RegBankSelect::computeMapping(
break;
}
}
DEBUG(dbgs() << "Total cost is: " << Cost << "\n");
return Cost;
}
@ -550,7 +558,7 @@ bool RegBankSelect::assignInstr(MachineInstr &MI) {
// Make sure the mapping is valid for MI.
assert(BestMapping.verify(MI) && "Invalid instruction mapping");
DEBUG(dbgs() << "Mapping: " << BestMapping << '\n');
DEBUG(dbgs() << "Best Mapping: " << BestMapping << '\n');
// After this call, MI may not be valid anymore.
// Do not use it.
@ -959,3 +967,20 @@ bool RegBankSelect::MappingCost::operator==(const MappingCost &Cost) const {
return LocalCost == Cost.LocalCost && NonLocalCost == Cost.NonLocalCost &&
LocalFreq == Cost.LocalFreq;
}
void RegBankSelect::MappingCost::dump() const {
print(dbgs());
dbgs() << '\n';
}
void RegBankSelect::MappingCost::print(raw_ostream &OS) const {
if (*this == ImpossibleCost()) {
OS << "impossible";
return;
}
if (isSaturated()) {
OS << "saturated";
return;
}
OS << LocalFreq << " * " << LocalCost << " + " << NonLocalCost;
}