[llvm] r373377 - [Dominators][CodeGen] Fix MachineDominatorTree preservation in PHIElimination

[Jakub Kuderski via llvm-commits]

Author: kuhar
Date: Tue Oct  1 11:27:17 2019
New Revision: 373377

URL: http://llvm.org/viewvc/llvm-project?rev=373377&view=rev
Log:
[Dominators][CodeGen] Fix MachineDominatorTree preservation in PHIElimination

Summary:
PHIElimination modifies CFG and marks MachineDominatorTree as preserved. Therefore, it the CFG changes it should also update the MDT, when available. This patch teaches PHIElimination to recalculate MDT when necessary.

This fixes the `tailmerging_in_mbp.ll` test failure discovered after switching to generic DomTree verification algorithm in MachineDominators in D67976.

Reviewers: arsenm, hliao, alex-t, rampitec, vpykhtin, grosser

Reviewed By: rampitec

Subscribers: MatzeB, wdng, hiraditya, javed.absar, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68154

Modified:
    llvm/trunk/lib/CodeGen/MachineScheduler.cpp
    llvm/trunk/lib/CodeGen/PHIElimination.cpp

Modified: llvm/trunk/lib/CodeGen/MachineScheduler.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineScheduler.cpp?rev=373377&r1=373376&r2=373377&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineScheduler.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineScheduler.cpp Tue Oct  1 11:27:17 2019
@@ -199,6 +199,7 @@ char &llvm::MachineSchedulerID = Machine
 INITIALIZE_PASS_BEGIN(MachineScheduler, DEBUG_TYPE,
                       "Machine Instruction Scheduler", false, false)
 INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
 INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
 INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
@@ -211,7 +212,7 @@ MachineScheduler::MachineScheduler() : M
 
 void MachineScheduler::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.setPreservesCFG();
-  AU.addRequiredID(MachineDominatorsID);
+  AU.addRequired<MachineDominatorTree>();
   AU.addRequired<MachineLoopInfo>();
   AU.addRequired<AAResultsWrapperPass>();
   AU.addRequired<TargetPassConfig>();
@@ -235,7 +236,7 @@ PostMachineScheduler::PostMachineSchedul
 
 void PostMachineScheduler::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.setPreservesCFG();
-  AU.addRequiredID(MachineDominatorsID);
+  AU.addRequired<MachineDominatorTree>();
   AU.addRequired<MachineLoopInfo>();
   AU.addRequired<TargetPassConfig>();
   MachineFunctionPass::getAnalysisUsage(AU);

Modified: llvm/trunk/lib/CodeGen/PHIElimination.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/PHIElimination.cpp?rev=373377&r1=373376&r2=373377&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/PHIElimination.cpp (original)
+++ llvm/trunk/lib/CodeGen/PHIElimination.cpp Tue Oct  1 11:27:17 2019
@@ -185,6 +185,11 @@ bool PHIElimination::runOnMachineFunctio
     MF.DeleteMachineInstr(I.first);
   }
 
+  // TODO: we should use the incremental DomTree updater here.
+  if (Changed)
+    if (auto *MDT = getAnalysisIfAvailable<MachineDominatorTree>())
+      MDT->getBase().recalculate(MF);
+
   LoweredPHIs.clear();
   ImpDefs.clear();
   VRegPHIUseCount.clear();