[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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@373377 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/MachineScheduler.cpp b/lib/CodeGen/MachineScheduler.cpp
index ff825c02438ac95e523b3e4508cab6451bd20b74..f0721ea3b76de20dcb34932b778dbb03d969f718 100644 (file)
--- a/lib/CodeGen/MachineScheduler.cpp
+++ b/lib/CodeGen/MachineScheduler.cpp
@@ -199,6 +199,7 @@ char &llvm::MachineSchedulerID = MachineScheduler::ID;
 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() : MachineSchedulerBase(ID) {
 
 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::PostMachineScheduler() : MachineSchedulerBase(ID) {
 
 void PostMachineScheduler::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.setPreservesCFG();
-  AU.addRequiredID(MachineDominatorsID);
+  AU.addRequired<MachineDominatorTree>();
   AU.addRequired<MachineLoopInfo>();
   AU.addRequired<TargetPassConfig>();
   MachineFunctionPass::getAnalysisUsage(AU);

diff --git a/lib/CodeGen/PHIElimination.cpp b/lib/CodeGen/PHIElimination.cpp
index 8ffd62b0d32cfdc61e197838dd679920f8f0a5c3..4dd4c4b1084e59db1fe6f354db6b561622dce5fd 100644 (file)
--- a/lib/CodeGen/PHIElimination.cpp
+++ b/lib/CodeGen/PHIElimination.cpp
@@ -185,6 +185,11 @@ bool PHIElimination::runOnMachineFunction(MachineFunction &MF) {
     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();