[llvm-commits] Patch: avoid reanalyze a node twice in LegalizeTypes

[Mon Ping Wang]

This patch is to fix an assert that we get for the test case below
   Assertion failed: (N->getNodeId() !=  
DAGTypeLegalizer::ReadyToProcess && N->getNodeId() !=
   DAGTypeLegalizer::Processed && "Invalid node ID for RAUW  
analysis!"), function ReplaceValue

In the DAG, we get is something like

%tmp1 = extract_subvector <2 x double> %tmp0,  <4 x double> %vec, 0
%tmp2 = extract_element <2 x double> %tmp1, 0
%tmp3 = extract_element <2 x double> %tmp1, 1
%tmp4 = build_vector<4 x double> %tmp2, %tmp3, %tmp?, %tmp?

We discover when examining the operands of %tmp1 that %vec is not a  
legal type and we split it.  This causes us to replace all uses of  
%tmp1 which triggers us update %tmp2 and %tmp3 and then update the  
%tmp4.  The problem is that when we do the update, we will add %tmp4  
node twice to UpdateListener (NodesToAnalyze) i..e, we add it when we  
process %tmp2 and again for %tmp3.  When walking through the nodes to  
reanalyze, the first time we see %tmp4, we update the NodeId to the  
NewNode.  When we encounter the node again through the list, we hit  
the assertion since we have already updated that Node.

The following patch fixes this by changing NodesToAnalyze from  
SmallVector to use SmallPtrSet to avoid duplicates.  Please let me  
know of any comments.

Thanks,
   -- Mon Ping



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