[PATCH] D111313: [AMDGPU] Preserve MachineDominatorTree in SILowerControlFlow

[Jay Foad via Phabricator via llvm-commits]

foad updated this revision to Diff 377883.
foad added a comment.

Also cope with splitting blocks.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D111313/new/

https://reviews.llvm.org/D111313

Files:
  llvm/lib/Target/AMDGPU/SILowerControlFlow.cpp
  llvm/test/CodeGen/AMDGPU/llc-pipeline.ll


Index: llvm/test/CodeGen/AMDGPU/llc-pipeline.ll
===================================================================
--- llvm/test/CodeGen/AMDGPU/llc-pipeline.ll
+++ llvm/test/CodeGen/AMDGPU/llc-pipeline.ll
@@ -316,7 +316,6 @@
 ; GCN-O1-NEXT:        Eliminate PHI nodes for register allocation
 ; GCN-O1-NEXT:        SI Lower control flow pseudo instructions
 ; GCN-O1-NEXT:        Two-Address instruction pass
-; GCN-O1-NEXT:        MachineDominator Tree Construction
 ; GCN-O1-NEXT:        Slot index numbering
 ; GCN-O1-NEXT:        Live Interval Analysis
 ; GCN-O1-NEXT:        Machine Natural Loop Construction
@@ -600,7 +599,6 @@
 ; GCN-O1-OPTS-NEXT:        Eliminate PHI nodes for register allocation
 ; GCN-O1-OPTS-NEXT:        SI Lower control flow pseudo instructions
 ; GCN-O1-OPTS-NEXT:        Two-Address instruction pass
-; GCN-O1-OPTS-NEXT:        MachineDominator Tree Construction
 ; GCN-O1-OPTS-NEXT:        Slot index numbering
 ; GCN-O1-OPTS-NEXT:        Live Interval Analysis
 ; GCN-O1-OPTS-NEXT:        Machine Natural Loop Construction
@@ -886,7 +884,6 @@
 ; GCN-O2-NEXT:        Eliminate PHI nodes for register allocation
 ; GCN-O2-NEXT:        SI Lower control flow pseudo instructions
 ; GCN-O2-NEXT:        Two-Address instruction pass
-; GCN-O2-NEXT:        MachineDominator Tree Construction
 ; GCN-O2-NEXT:        Slot index numbering
 ; GCN-O2-NEXT:        Live Interval Analysis
 ; GCN-O2-NEXT:        Machine Natural Loop Construction
@@ -1186,7 +1183,6 @@
 ; GCN-O3-NEXT:        Eliminate PHI nodes for register allocation
 ; GCN-O3-NEXT:        SI Lower control flow pseudo instructions
 ; GCN-O3-NEXT:        Two-Address instruction pass
-; GCN-O3-NEXT:        MachineDominator Tree Construction
 ; GCN-O3-NEXT:        Slot index numbering
 ; GCN-O3-NEXT:        Live Interval Analysis
 ; GCN-O3-NEXT:        Machine Natural Loop Construction
Index: llvm/lib/Target/AMDGPU/SILowerControlFlow.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/SILowerControlFlow.cpp
+++ llvm/lib/Target/AMDGPU/SILowerControlFlow.cpp
@@ -52,6 +52,7 @@
 #include "MCTargetDesc/AMDGPUMCTargetDesc.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/CodeGen/LiveIntervals.h"
+#include "llvm/CodeGen/MachineDominators.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 
 using namespace llvm;
@@ -69,6 +70,7 @@
   const SIRegisterInfo *TRI = nullptr;
   const SIInstrInfo *TII = nullptr;
   LiveIntervals *LIS = nullptr;
+  MachineDominatorTree *MDT = nullptr;
   MachineRegisterInfo *MRI = nullptr;
   SetVector<MachineInstr*> LoweredEndCf;
   DenseSet<Register> LoweredIf;
@@ -141,6 +143,7 @@
 
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     // Should preserve the same set that TwoAddressInstructions does.
+    AU.addPreserved<MachineDominatorTree>();
     AU.addPreserved<SlotIndexes>();
     AU.addPreserved<LiveIntervals>();
     AU.addPreservedID(LiveVariablesID);
@@ -471,6 +474,14 @@
   MachineBasicBlock *SplitBB = &MBB;
   if (NeedBlockSplit) {
     SplitBB = MBB.splitAt(MI, /*UpdateLiveIns*/true, LIS);
+    if (MDT && SplitBB != &MBB) {
+      MachineDomTreeNode *MBBNode = (*MDT)[&MBB];
+      SmallVector<MachineDomTreeNode *> Children(MBBNode->begin(),
+                                                 MBBNode->end());
+      MachineDomTreeNode *SplitBBNode = MDT->addNewBlock(SplitBB, &MBB);
+      for (MachineDomTreeNode *Child : Children)
+        MDT->changeImmediateDominator(Child, SplitBBNode);
+    }
     Opcode = OrTermrOpc;
     InsPt = MI;
   }
@@ -757,6 +768,8 @@
     for (auto &I : MBB.instrs())
       LIS->RemoveMachineInstrFromMaps(I);
   }
+  if (MDT)
+    MDT->eraseNode(&MBB);
   MBB.clear();
   MBB.eraseFromParent();
   if (FallThrough && !FallThrough->isLayoutSuccessor(Succ)) {
@@ -780,6 +793,7 @@
 
   // This doesn't actually need LiveIntervals, but we can preserve them.
   LIS = getAnalysisIfAvailable<LiveIntervals>();
+  MDT = getAnalysisIfAvailable<MachineDominatorTree>();
   MRI = &MF.getRegInfo();
   BoolRC = TRI->getBoolRC();
 


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