[PATCH] D136267: [AMDGPU] Speedup GCNDownwardRPTracker::advanceBeforeNext

[Valery Pykhtin via Phabricator via llvm-commits]

vpykhtin created this revision.
vpykhtin added reviewers: rampitec, kerbowa, arsenm.
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The function makes liveness tests for the entire live register set for every instruction it passes by.
This becomes very slow on high RP regions such as ASAN enabled code.

Instead only uses of last tracked instruction should be tested and this greatly improves compilation time.

This patch revealed few bugs in SIFormMemoryClauses and PreRARematStage::sinkTriviallyRematInsts which should 
be fixed first.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D136267

Files:
  llvm/lib/Target/AMDGPU/GCNRegPressure.cpp


Index: llvm/lib/Target/AMDGPU/GCNRegPressure.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/GCNRegPressure.cpp
+++ llvm/lib/Target/AMDGPU/GCNRegPressure.cpp
@@ -354,6 +354,11 @@
 
 bool GCNDownwardRPTracker::advanceBeforeNext() {
   assert(MRI && "call reset first");
+  if (!LastTrackedMI)
+    return true;
+
+  auto const RegUses = collectVirtualRegUses(*LastTrackedMI, LIS, *MRI);
+  // each RegUnit is unique in RegUses
 
   NextMI = skipDebugInstructionsForward(NextMI, MBBEnd);
   if (NextMI == MBBEnd)
@@ -363,23 +368,29 @@
   assert(SI.isValid());
 
   // Remove dead registers or mask bits.
-  for (auto &It : LiveRegs) {
-    const LiveInterval &LI = LIS.getInterval(It.first);
+  for (auto &U : RegUses) {
+    const LiveInterval &LI = LIS.getInterval(U.RegUnit);
     if (LI.hasSubRanges()) {
+      auto It = LiveRegs.end();
       for (const auto &S : LI.subranges()) {
         if (!S.liveAt(SI)) {
-          auto PrevMask = It.second;
-          It.second &= ~S.LaneMask;
-          CurPressure.inc(It.first, PrevMask, It.second, *MRI);
+          if (It == LiveRegs.end()) {
+            It = LiveRegs.find(U.RegUnit);
+            assert(It != LiveRegs.end());
+          }
+          auto PrevMask = It->second;
+          It->second &= ~S.LaneMask;
+          CurPressure.inc(U.RegUnit, PrevMask, It->second, *MRI);
         }
       }
+      if (It != LiveRegs.end() && It->second.none())
+        LiveRegs.erase(It);
     } else if (!LI.liveAt(SI)) {
-      auto PrevMask = It.second;
-      It.second = LaneBitmask::getNone();
-      CurPressure.inc(It.first, PrevMask, It.second, *MRI);
+      auto It = LiveRegs.find(U.RegUnit);
+      assert(It != LiveRegs.end());
+      CurPressure.inc(U.RegUnit, It->second, LaneBitmask::getNone(), *MRI);
+      LiveRegs.erase(It);
     }
-    if (It.second.none())
-      LiveRegs.erase(It.first);
   }
 
   MaxPressure = max(MaxPressure, CurPressure);


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