Restore hasPostISelHook tblgen flag.

No functionality change. The hook makes it explicit which patterns
require "special" handling. i.e. it self-documents tblgen
deficiencies. I plan to add verification in ExpandISelPseudos and
Thumb2SizeReduce to catch any missing hasPostISelHooks. Otherwise it's
too fragile.

llvm-svn: 140160

1 files changed, 6 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 9f2369d142d..b684619776f 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -179,7 +179,12 @@ TargetLowering::EmitInstrWithCustomInserter(MachineInstr *MI,
 
 void TargetLowering::AdjustInstrPostInstrSelection(MachineInstr *MI,
                                                    SDNode *Node) const {
-  // Do nothing unless the target overrides it.
+#ifndef NDEBUG
+  dbgs() << "If a target marks an instruction with "
+          "'hasPostISelHook', it must implement "
+          "TargetLowering::AdjustInstrPostInstrSelection!";
+#endif
+  llvm_unreachable(0);
 }
 
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