[PATCH] D68154: [Dominators][CodeGen] Fix MachineDominatorTree preservation in PHIElimination

[Jakub Kuderski via Phabricator via llvm-commits]

kuhar created this revision.
kuhar added reviewers: arsenm, hliao, alex-t, rampitec, vpykhtin.
Herald added subscribers: javed.absar, hiraditya, wdng, MatzeB.
Herald added a reviewer: grosser.
Herald added a project: LLVM.

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 <https://reviews.llvm.org/D67976>.


Repository:
  rL LLVM

https://reviews.llvm.org/D68154

Files:
  llvm/lib/CodeGen/MachineScheduler.cpp
  llvm/lib/CodeGen/PHIElimination.cpp
  llvm/test/CodeGen/AArch64/tailmerging_in_mbp.ll


Index: llvm/test/CodeGen/AArch64/tailmerging_in_mbp.ll
===================================================================
--- llvm/test/CodeGen/AArch64/tailmerging_in_mbp.ll
+++ llvm/test/CodeGen/AArch64/tailmerging_in_mbp.ll
@@ -1,5 +1,4 @@
 ; RUN: llc <%s -mtriple=aarch64-eabi -verify-machine-dom-info | FileCheck %s
-; XFAIL: *
 
 ; CHECK-LABEL: test:
 ; CHECK-LABEL: %cond.false12.i
Index: llvm/lib/CodeGen/PHIElimination.cpp
===================================================================
--- llvm/lib/CodeGen/PHIElimination.cpp
+++ llvm/lib/CodeGen/PHIElimination.cpp
@@ -148,6 +148,7 @@
   MRI = &MF.getRegInfo();
   LV = getAnalysisIfAvailable<LiveVariables>();
   LIS = getAnalysisIfAvailable<LiveIntervals>();
+  auto *MDT = getAnalysisIfAvailable<MachineDominatorTree>();
 
   bool Changed = false;
 
@@ -185,6 +186,9 @@
     MF.DeleteMachineInstr(I.first);
   }
 
+  if (Changed && MDT)
+    MDT->getBase().recalculate(MF);
+
   LoweredPHIs.clear();
   ImpDefs.clear();
   VRegPHIUseCount.clear();
Index: llvm/lib/CodeGen/MachineScheduler.cpp
===================================================================
--- llvm/lib/CodeGen/MachineScheduler.cpp
+++ llvm/lib/CodeGen/MachineScheduler.cpp
@@ -198,6 +198,7 @@
 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)
@@ -210,7 +211,7 @@
 
 void MachineScheduler::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.setPreservesCFG();
-  AU.addRequiredID(MachineDominatorsID);
+  AU.addRequired<MachineDominatorTree>();
   AU.addRequired<MachineLoopInfo>();
   AU.addRequired<AAResultsWrapperPass>();
   AU.addRequired<TargetPassConfig>();
@@ -234,7 +235,7 @@
 
 void PostMachineScheduler::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.setPreservesCFG();
-  AU.addRequiredID(MachineDominatorsID);
+  AU.addRequired<MachineDominatorTree>();
   AU.addRequired<MachineLoopInfo>();
   AU.addRequired<TargetPassConfig>();
   MachineFunctionPass::getAnalysisUsage(AU);


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