1 files changed, 11 insertions, 1 deletions
diff --git a/llvm/lib/Target/AMDGPU/GCNSchedStrategy.cpp b/llvm/lib/Target/AMDGPU/GCNSchedStrategy.cpp
index c0a6765df34..e9afe2a2b11 100644
--- a/llvm/lib/Target/AMDGPU/GCNSchedStrategy.cpp
+++ b/llvm/lib/Target/AMDGPU/GCNSchedStrategy.cpp
@@ -372,13 +372,23 @@ void GCNScheduleDAGMILive::schedule() {
   // We could not keep current target occupancy because of the just scheduled
   // region. Record new occupancy for next scheduling cycle.
   unsigned NewOccupancy = std::max(WavesAfter, WavesBefore);
+  // Allow memory bound functions to drop to 4 waves if not limited by an
+  // attribute.
+  unsigned MinMemBoundWaves = std::max(MFI.getMinWavesPerEU(), 4u);
+  if (WavesAfter < WavesBefore && WavesAfter < MinOccupancy &&
+      WavesAfter >= MinMemBoundWaves &&
+      (MFI.isMemoryBound() || MFI.needsWaveLimiter())) {
+    LLVM_DEBUG(dbgs() << "Function is memory bound, allow occupancy drop up to "
+                      << MinMemBoundWaves << " waves\n");
+    NewOccupancy = WavesAfter;
+  }
   if (NewOccupancy < MinOccupancy) {
     MinOccupancy = NewOccupancy;
     LLVM_DEBUG(dbgs() << "Occupancy lowered for the function to "
                       << MinOccupancy << ".\n");
   }
 
-  if (WavesAfter >= WavesBefore) {
+  if (WavesAfter >= MinOccupancy) {
     Pressure[RegionIdx] = PressureAfter;
     return;
   }