================
@@ -1029,8 +1029,13 @@ GCNScheduleDAGMILive::getRealRegPressure(unsigned
RegionIdx) const {
if (Regions[RegionIdx].first == Regions[RegionIdx].second)
return llvm::getRegPressure(MRI, LiveIns[RegionIdx]);
GCNDownwardRPTracker RPTracker(*LIS);
- RPTracker.advance(Regions[RegionIdx].first, Regions[RegionIdx].second,
- &LiveIns[RegionIdx]);
+ if (!RPTracker.advance(Regions[RegionIdx].first, Regions[RegionIdx].second,
+ &LiveIns[RegionIdx])) {
+ // Advance can produce false on a non-empty region if all MIs in the region
+ // are debug values; in such cases the maintained max pressure is invalid
+ // and the only source of pressure are the region's live-ins.
----------------
lucas-rami wrote:
It's possible for the RP tracker to compute the correct pressure when a
`LiveRegSet` is provided to advance/reset, since it can just call
`llvm::getRegPressure`. When a `LiveRegSet` is not provided however, the
tracker must look for a `SlotIndex` at which to estimate pressure. When there
are no non-debug MIs in the block, I don't see a way to derive such an index
and therefore to compute the correct pressure. It felt weird to me to have this
dependency on `LiveRegSet` to be able to compute the correct pressure in such
cases.
https://github.com/llvm/llvm-project/pull/196099
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