[AMDGPU] Track liveins for max-ilp-sched-strategy

[jrbyrnes]

Summary

Even if optimizing for ILP, it is still useful to track RP to avoid spilling. Given that, we need to maintin consistent liveness state with the RP tracker. This patch makes RP tracking consistent by updating for liveins.

Otherwise, we should completely eliminate RP tracking for this scheduler (checkScheduling, initCandidate).

[rampitec]

LGTM with couple nits.

llvm/test/CodeGen/AMDGPU/schedule-ilp-liveness-tracking.mir

3

Please remove double whitespace before -run-pass.

35

Please remove blank line.

[jrbyrnes]

Nits

[rampitec]

llvm/test/CodeGen/AMDGPU/schedule-ilp-liveness-tracking.mir

34

Something wrong going on with this newline. Was it DOS style and now missing?

[jrbyrnes]

Pesky newline

llvm/lib/Target/AMDGPU/GCNSchedStrategy.cpp

 void GCNSchedStage::setupNewBlock() {
   if (CurrentMBB)
     DAG.finishBlock();
 
   CurrentMBB = DAG.RegionBegin->getParent();
   DAG.startBlock(CurrentMBB);
   // Get real RP for the region if it hasn't be calculated before. After the
   // initial schedule stage real RP will be collected after scheduling.
-  if (StageID == GCNSchedStageID::OccInitialSchedule)
+  if (StageID == GCNSchedStageID::OccInitialSchedule ||
+      StageID == GCNSchedStageID::ILPInitialSchedule)
     DAG.computeBlockPressure(RegionIdx, CurrentMBB);
 }
 
 void GCNSchedStage::finalizeGCNRegion() {
   DAG.Regions[RegionIdx] = std::pair(DAG.RegionBegin, DAG.RegionEnd);
   DAG.RescheduleRegions[RegionIdx] = false;
   if (S.HasHighPressure)
     DAG.RegionsWithHighRP[RegionIdx] = true;

llvm/test/CodeGen/AMDGPU/schedule-ilp-liveness-tracking.mir

+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 2
+# RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx90a -amdgpu-enable-max-ilp-scheduling-strategy -verify-machineinstrs -run-pass=machine-scheduler -verify-misched -o - %s | FileCheck %s
+
+---
+name:            max-ilp-liveness-tracking
+tracksRegLiveness: true
+body:             |
+  ; CHECK-LABEL: name: max-ilp-liveness-tracking
+  ; CHECK: bb.0:
+  ; CHECK-NEXT:   successors: %bb.1(0x80000000)
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   %src0:vgpr_32 = V_MOV_B32_e64 0, implicit $exec
+  ; CHECK-NEXT:   %src1:vgpr_32 = V_MOV_B32_e64 1, implicit $exec
+  ; CHECK-NEXT:   %live0:vgpr_32 = V_ADD_U32_e32 %src0, %src1, implicit $exec
+  ; CHECK-NEXT:   %live1:vgpr_32 = V_ADD_U32_e32 %live0, %src1, implicit $exec
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.1:
+  ; CHECK-NEXT:   %out0:vgpr_32 = V_ADD_U32_e32 %live0, %live1, implicit $exec
+  ; CHECK-NEXT:   dead %out1:vgpr_32 = V_ADD_U32_e32 %out0, %live1, implicit $exec
+  ; CHECK-NEXT:   S_ENDPGM 0
+  bb.0:
+    successors: %bb.1
+    %src0:vgpr_32 = V_MOV_B32_e64 0, implicit $exec
+    %src1:vgpr_32 = V_MOV_B32_e64 1, implicit $exec
+    %live0:vgpr_32 = V_ADD_U32_e32 %src0:vgpr_32, %src1:vgpr_32, implicit $exec
+    %live1:vgpr_32 = V_ADD_U32_e32 %live0:vgpr_32, %src1:vgpr_32, implicit $exec
+
+  bb.1:
+    %out0:vgpr_32 = V_ADD_U32_e32 %live0:vgpr_32, %live1:vgpr_32, implicit $exec
+    %out1:vgpr_32 = V_ADD_U32_e32 %out0:vgpr_32, %live1:vgpr_32, implicit $exec
+    S_ENDPGM 0
+
+...
 No newline at end of file