[PATCH] D66750: [CodeGen] Introduce MachineBasicBlock::updatePHIs helper and use it. NFC

[Bjorn Pettersson via Phabricator via llvm-commits]

bjope created this revision.
bjope added reviewers: t.p.northover, arsenm, uabelho.
Herald added subscribers: jsji, hiraditya, wdng.
Herald added a project: LLVM.

Found a couple of places in the code where all the PHI nodes
of a MBB is updated, replacing references to one MBB by
reference to another MBB instead.

This patch simply refactors the code to use a common helper
(MachineBasicBlock::updatePHIs) for such PHI node updates.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D66750

Files:
  llvm/include/llvm/CodeGen/MachineBasicBlock.h
  llvm/lib/CodeGen/MachineBasicBlock.cpp
  llvm/lib/CodeGen/MachinePipeliner.cpp


Index: llvm/lib/CodeGen/MachinePipeliner.cpp
===================================================================
--- llvm/lib/CodeGen/MachinePipeliner.cpp
+++ llvm/lib/CodeGen/MachinePipeliner.cpp
@@ -2234,15 +2234,7 @@
   }
 
   // Fix any Phi nodes in the loop exit block.
-  for (MachineInstr &MI : *LoopExitBB) {
-    if (!MI.isPHI())
-      break;
-    for (unsigned i = 2, e = MI.getNumOperands() + 1; i != e; i += 2) {
-      MachineOperand &MO = MI.getOperand(i);
-      if (MO.getMBB() == BB)
-        MO.setMBB(PredBB);
-    }
-  }
+  LoopExitBB->updatePHIs(BB, PredBB);
 
   // Create a branch to the new epilog from the kernel.
   // Remove the original branch and add a new branch to the epilog.
Index: llvm/lib/CodeGen/MachineBasicBlock.cpp
===================================================================
--- llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -771,6 +771,16 @@
   Predecessors.erase(I);
 }
 
+void MachineBasicBlock::updatePHIs(MachineBasicBlock *FromMBB,
+                                   MachineBasicBlock *ToMBB) {
+  for (MachineInstr &MI : phis())
+    for (unsigned i = 2, e = MI.getNumOperands() + 1; i != e; i += 2) {
+      MachineOperand &MO = MI.getOperand(i);
+      if (MO.getMBB() == FromMBB)
+        MO.setMBB(ToMBB);
+    }
+}
+
 void MachineBasicBlock::transferSuccessors(MachineBasicBlock *FromMBB) {
   if (this == FromMBB)
     return;
@@ -778,7 +788,8 @@
   while (!FromMBB->succ_empty()) {
     MachineBasicBlock *Succ = *FromMBB->succ_begin();
 
-    // If probability list is empty it means we don't use it (disabled optimization).
+    // If probability list is empty it means we don't use it (disabled
+    // optimization).
     if (!FromMBB->Probs.empty()) {
       auto Prob = *FromMBB->Probs.begin();
       addSuccessor(Succ, Prob);
@@ -804,13 +815,7 @@
     FromMBB->removeSuccessor(Succ);
 
     // Fix up any PHI nodes in the successor.
-    for (MachineBasicBlock::instr_iterator MI = Succ->instr_begin(),
-           ME = Succ->instr_end(); MI != ME && MI->isPHI(); ++MI)
-      for (unsigned i = 2, e = MI->getNumOperands()+1; i != e; i += 2) {
-        MachineOperand &MO = MI->getOperand(i);
-        if (MO.getMBB() == FromMBB)
-          MO.setMBB(this);
-      }
+    Succ->updatePHIs(FromMBB, this);
   }
   normalizeSuccProbs();
 }
@@ -985,13 +990,8 @@
     }
   }
 
-  // Fix PHI nodes in Succ so they refer to NMBB instead of this
-  for (MachineBasicBlock::instr_iterator
-         i = Succ->instr_begin(),e = Succ->instr_end();
-       i != e && i->isPHI(); ++i)
-    for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2)
-      if (i->getOperand(ni+1).getMBB() == this)
-        i->getOperand(ni+1).setMBB(NMBB);
+  // Fix PHI nodes in Succ so they refer to NMBB instead of this.
+  Succ->updatePHIs(this, NMBB);
 
   // Inherit live-ins from the successor
   for (const auto &LI : Succ->liveins())
Index: llvm/include/llvm/CodeGen/MachineBasicBlock.h
===================================================================
--- llvm/include/llvm/CodeGen/MachineBasicBlock.h
+++ llvm/include/llvm/CodeGen/MachineBasicBlock.h
@@ -492,6 +492,10 @@
   void splitSuccessor(MachineBasicBlock *Old, MachineBasicBlock *New,
                       bool NormalizeSuccProbs = false);
 
+  /// Update PHI nodes in this MBB to refer to ToMBB instead of FromMBB.
+  void updatePHIs(MachineBasicBlock *FromMBB,
+                  MachineBasicBlock *ToMBB);
+
   /// Transfers all the successors from MBB to this machine basic block (i.e.,
   /// copies all the successors FromMBB and remove all the successors from
   /// FromMBB).


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