[PATCH] D145006: [GISel][CSE][NFC]: Handle mutual recursion when inserting node

[Aditya Nandakumar via Phabricator via llvm-commits]

aditya_nandakumar created this revision.
aditya_nandakumar added reviewers: arsenm, aemerson, paquette, foad, dsanders.
Herald added subscribers: StephenFan, hiraditya.
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aditya_nandakumar requested review of this revision.
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GISel's CSE mechanism lazily inserts instructions into the CSE List to improve on efficiency as well as efficacy of CSE (for allowing partially built instructions to be fully built). There's unfortunately a mutual recursion via
`handleRecordedInsts -> handleRecordedInst -> insertNode-> handleRecordedInsts`.
So this change simply records that we're already draining this list so we can just bail out on the recursion.
No changes to codegen are expected as we're still draining/handling the temporary list via `pop_back` and we should get the same sequence of instructions whether we call pop_back in a loop at the top level or recursive.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D145006

Files:
  llvm/include/llvm/CodeGen/GlobalISel/CSEInfo.h
  llvm/lib/CodeGen/GlobalISel/CSEInfo.cpp


Index: llvm/lib/CodeGen/GlobalISel/CSEInfo.cpp
===================================================================
--- llvm/lib/CodeGen/GlobalISel/CSEInfo.cpp
+++ llvm/lib/CodeGen/GlobalISel/CSEInfo.cpp
@@ -217,10 +217,14 @@
 }
 
 void GISelCSEInfo::handleRecordedInsts() {
+  if (HandlingRecordedInstrs)
+    return;
+  HandlingRecordedInstrs = true;
   while (!TemporaryInsts.empty()) {
     auto *MI = TemporaryInsts.pop_back_val();
     handleRecordedInst(MI);
   }
+  HandlingRecordedInstrs = false;
 }
 
 bool GISelCSEInfo::shouldCSE(unsigned Opc) const {
Index: llvm/include/llvm/CodeGen/GlobalISel/CSEInfo.h
===================================================================
--- llvm/include/llvm/CodeGen/GlobalISel/CSEInfo.h
+++ llvm/include/llvm/CodeGen/GlobalISel/CSEInfo.h
@@ -111,6 +111,8 @@
   /// into the CSEMap. MI should return true for shouldCSE(MI->getOpcode())
   void insertInstr(MachineInstr *MI, void *InsertPos = nullptr);
 
+  bool HandlingRecordedInstrs = false;
+
 public:
   GISelCSEInfo() = default;
 


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