[PATCH] D119934: [RISCV][NFC] Fix a mistake in PostprocessISelDAG

[Haocong Lu via Phabricator via llvm-commits]

Luhaocong created this revision.
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With the condition `N->use_empty()` , the root node of DAG always misses peephole optimization.
A dummy node is needed here.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D119934

Files:
  llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp


Index: llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
+++ llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
@@ -130,6 +130,7 @@
 }
 
 void RISCVDAGToDAGISel::PostprocessISelDAG() {
+  HandleSDNode Dummy(CurDAG->getRoot());
   SelectionDAG::allnodes_iterator Position = CurDAG->allnodes_end();
 
   bool MadeChange = false;
@@ -144,6 +145,8 @@
     MadeChange |= doPeepholeMaskedRVV(N);
   }
 
+  CurDAG->setRoot(Dummy.getValue());
+
   if (MadeChange)
     CurDAG->RemoveDeadNodes();
 }


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