[llvm] r296668 - [DAG] Prevent Stale nodes from entering worklist

[Nirav Dave via llvm-commits]

Author: niravd
Date: Wed Mar  1 14:19:38 2017
New Revision: 296668

URL: http://llvm.org/viewvc/llvm-project?rev=296668&view=rev
Log:
[DAG] Prevent Stale nodes from entering worklist

Add check that deleted nodes do not get added to worklist. This can
occur when a node's operand is simplified to an existing node.

This fixes PR32108.

Reviewers: jyknight, hfinkel, chandlerc

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D30506

Added:
    llvm/trunk/test/CodeGen/X86/pr32108.ll
Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=296668&r1=296667&r2=296668&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Wed Mar  1 14:19:38 2017
@@ -129,6 +129,9 @@ namespace {
     /// Add to the worklist making sure its instance is at the back (next to be
     /// processed.)
     void AddToWorklist(SDNode *N) {
+      assert(N->getOpcode() != ISD::DELETED_NODE &&
+             "Deleted Node added to Worklist");
+
       // Skip handle nodes as they can't usefully be combined and confuse the
       // zero-use deletion strategy.
       if (N->getOpcode() == ISD::HANDLENODE)
@@ -12619,10 +12622,13 @@ SDValue DAGCombiner::visitSTORE(SDNode *
             Value,
             APInt::getLowBitsSet(Value.getScalarValueSizeInBits(),
                                  ST->getMemoryVT().getScalarSizeInBits()))) {
-      // Re-visit the store if anything changed; SimplifyDemandedBits
-      // will add Value's node back to the worklist if necessary, but
-      // we also need to re-visit the Store node itself.
-      AddToWorklist(N);
+      // Re-visit the store if anything changed and the store hasn't
+      // been merged with another node (N is deleted);
+      // SimplifyDemandedBits will add Value's node back to the
+      // worklist if necessary, but we also need to re-visit the Store
+      // node itself.
+      if (N->getOpcode() != ISD::DELETED_NODE)
+        AddToWorklist(N);
       return SDValue(N, 0);
     }
   }

Added: llvm/trunk/test/CodeGen/X86/pr32108.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/pr32108.ll?rev=296668&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/pr32108.ll (added)
+++ llvm/trunk/test/CodeGen/X86/pr32108.ll Wed Mar  1 14:19:38 2017
@@ -0,0 +1,20 @@
+; RUN: llc -march=x86-64 %s -o -
+
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @autogen_SD1794() {
+BB:
+  %Cmp45 = icmp slt <4 x i32> undef, undef
+  br label %CF243
+
+CF243:                                            ; preds = %CF243, %BB
+  br i1 undef, label %CF243, label %CF257
+
+CF257:                                            ; preds = %CF243
+  %Shuff144 = shufflevector <4 x i1> undef, <4 x i1> %Cmp45, <4 x i32> <i32 undef, i32 undef, i32 5, i32 undef>
+  br label %CF244
+
+CF244:                                            ; preds = %CF244, %CF257
+  %Shuff182 = shufflevector <4 x i1> %Shuff144, <4 x i1> zeroinitializer, <4 x i32> <i32 3, i32 5, i32 7, i32 undef>
+  br label %CF244
+}