[PATCH] D128539: [GISel] Don't fold convergent instruction across CFG

[Quentin Colombet via Phabricator via llvm-commits]

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Before merging two instructions together, GISel does some sanity checks that the folding is legal.
However that check was missing that the source of the pattern may be convergent. When the destination location is in a different basic block, the folding is invalid.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D128539

Files:
  llvm/lib/CodeGen/GlobalISel/InstructionSelector.cpp


Index: llvm/lib/CodeGen/GlobalISel/InstructionSelector.cpp
===================================================================
--- llvm/lib/CodeGen/GlobalISel/InstructionSelector.cpp
+++ llvm/lib/CodeGen/GlobalISel/InstructionSelector.cpp
@@ -59,6 +59,10 @@
       std::next(MI.getIterator()) == IntoMI.getIterator())
     return true;
 
+  // Convergent instructions cannot be moved in the CFG.
+  if (MI.isConvergent() && MI.getParent() != IntoMI.getParent())
+    return false;
+
   return !MI.mayLoadOrStore() && !MI.mayRaiseFPException() &&
          !MI.hasUnmodeledSideEffects() && MI.implicit_operands().empty();
 }


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