[globalisel] Restore comment explaining the nits of GISelChangeObserver::createdInstr()

llvm-svn: 353741

1 files changed, 8 insertions, 1 deletions

diff --git a/llvm/include/llvm/CodeGen/GlobalISel/GISelChangeObserver.h b/llvm/include/llvm/CodeGen/GlobalISel/GISelChangeObserver.h
index a2876b62127..e5691cb3517 100644
--- a/llvm/include/llvm/CodeGen/GlobalISel/GISelChangeObserver.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/GISelChangeObserver.h
@@ -33,10 +33,17 @@ public:
 
   /// An instruction is about to be erased.
   virtual void erasingInstr(MachineInstr &MI) = 0;
-  /// An instruction was created and inserted into the function.
+
+  /// An instruction has been created and inserted into the function.
+  /// Note that the instruction might not be a fully fledged instruction at this
+  /// point and won't be if the MachineFunction::Delegate is calling it. This is
+  /// because the delegate only sees the construction of the MachineInstr before
+  /// operands have been added.
   virtual void createdInstr(MachineInstr &MI) = 0;
+
   /// This instruction is about to be mutated in some way.
   virtual void changingInstr(MachineInstr &MI) = 0;
+
   /// This instruction was mutated in some way.
   virtual void changedInstr(MachineInstr &MI) = 0;