[CodeGen] assume max/default throughput for unspecified instructions
This is a fix for the problem arising in D47374 (PR37678):
https://bugs.llvm.org/show_bug.cgi?id=37678
We may not have throughput info because it's not specified in the model
or it's not available with variant scheduling, so assume that those
instructions can execute/complete at max-issue-width.
Differential Revision: https://reviews.llvm.org/D47723
llvm-svn: 334055
diff --git a/llvm/lib/MC/MCSchedule.cpp b/llvm/lib/MC/MCSchedule.cpp
index e3fa76e..929bd7f 100644
--- a/llvm/lib/MC/MCSchedule.cpp
+++ b/llvm/lib/MC/MCSchedule.cpp
@@ -85,7 +85,7 @@
llvm_unreachable("unsupported variant scheduling class");
}
-Optional<double>
+double
MCSchedModel::getReciprocalThroughput(const MCSubtargetInfo &STI,
const MCSchedClassDesc &SCDesc) {
Optional<double> Throughput;
@@ -99,18 +99,25 @@
double Temp = NumUnits * 1.0 / I->Cycles;
Throughput = Throughput ? std::min(Throughput.getValue(), Temp) : Temp;
}
- return Throughput ? 1 / Throughput.getValue() : Throughput;
+ if (Throughput.hasValue())
+ return 1.0 / Throughput.getValue();
+
+ // If no throughput value was calculated, assume that we can execute at the
+ // maximum issue width scaled by number of micro-ops for the schedule class.
+ return ((double)SCDesc.NumMicroOps) / SM.IssueWidth;
}
-Optional<double>
+double
MCSchedModel::getReciprocalThroughput(const MCSubtargetInfo &STI,
const MCInstrInfo &MCII,
const MCInst &Inst) const {
- Optional<double> Throughput;
unsigned SchedClass = MCII.get(Inst.getOpcode()).getSchedClass();
const MCSchedClassDesc *SCDesc = getSchedClassDesc(SchedClass);
+
+ // If there's no valid class, assume that the instruction executes/completes
+ // at the maximum issue width.
if (!SCDesc->isValid())
- return Throughput;
+ return 1.0 / IssueWidth;
unsigned CPUID = getProcessorID();
while (SCDesc->isVariant()) {
@@ -124,7 +131,7 @@
llvm_unreachable("unsupported variant scheduling class");
}
-Optional<double>
+double
MCSchedModel::getReciprocalThroughput(unsigned SchedClass,
const InstrItineraryData &IID) {
Optional<double> Throughput;
@@ -136,5 +143,10 @@
double Temp = countPopulation(I->getUnits()) * 1.0 / I->getCycles();
Throughput = Throughput ? std::min(Throughput.getValue(), Temp) : Temp;
}
- return Throughput ? 1 / Throughput.getValue() : Throughput;
+ if (Throughput.hasValue())
+ return 1.0 / Throughput.getValue();
+
+ // If there are no execution resources specified for this class, then assume
+ // that it can execute at the maximum default issue width.
+ return 1.0 / DefaultIssueWidth;
}