ADT: Guarantee transferNodesFromList is only called on transfers

Guarantee that ilist_traits<T>::transferNodesFromList is only called
when nodes are actually changing lists.

I also moved all the callbacks to occur *first*, before the operation.
This is the only choice for iplist<T>::merge, so we might as well be
consistent.  I expect this to have no effect in practice, although it
simplifies the logic in both iplist<T>::transfer and iplist<T>::insert.

llvm-svn: 280122

2 files changed, 3 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index 29f3594ddae..8d34360b331 100644
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -122,9 +122,8 @@ transferNodesFromList(ilist_traits<MachineInstr> &FromList,
                       ilist_iterator<MachineInstr> Last) {
   assert(Parent->getParent() == FromList.Parent->getParent() &&
         "MachineInstr parent mismatch!");
-
-  // Splice within the same MBB -> no change.
-  if (Parent == FromList.Parent) return;
+  assert(this != &FromList && "Called without a real transfer...");
+  assert(Parent != FromList.Parent && "Two lists have the same parent?");
 
   // If splicing between two blocks within the same function, just update the
   // parent pointers.
diff --git a/llvm/lib/IR/SymbolTableListTraitsImpl.h b/llvm/lib/IR/SymbolTableListTraitsImpl.h
index 50573d8d688..a55cf6a35a0 100644
--- a/llvm/lib/IR/SymbolTableListTraitsImpl.h
+++ b/llvm/lib/IR/SymbolTableListTraitsImpl.h
@@ -85,7 +85,7 @@ void SymbolTableListTraits<ValueSubClass>::transferNodesFromList(
     ilist_iterator<ValueSubClass> last) {
   // We only have to do work here if transferring instructions between BBs
   ItemParentClass *NewIP = getListOwner(), *OldIP = L2.getListOwner();
-  if (NewIP == OldIP) return;  // No work to do at all...
+  assert(NewIP != OldIP && "Expected different list owners");
 
   // We only have to update symbol table entries if we are transferring the
   // instructions to a different symtab object...