[llvm] r293522 - SDAG: Update ChainNodesMatched during UpdateChains if a node is replaced

[Justin Bogner via llvm-commits]

Author: bogner
Date: Mon Jan 30 12:29:46 2017
New Revision: 293522

URL: http://llvm.org/viewvc/llvm-project?rev=293522&view=rev
Log:
SDAG: Update ChainNodesMatched during UpdateChains if a node is replaced

Previously, we would hit UB (or the ISD::DELETED_NODE assert) if we
happened to replace a node during UpdateChains, because it would be
left in the list we were iterating over. This nulls out the pointer
when that happens so that we can avoid the issue.

Fixes llvm.org/PR31710

Added:
    llvm/trunk/test/CodeGen/SystemZ/pr31710.ll
Modified:
    llvm/trunk/include/llvm/CodeGen/SelectionDAGISel.h
    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

Modified: llvm/trunk/include/llvm/CodeGen/SelectionDAGISel.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/SelectionDAGISel.h?rev=293522&r1=293521&r2=293522&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/SelectionDAGISel.h (original)
+++ llvm/trunk/include/llvm/CodeGen/SelectionDAGISel.h Mon Jan 30 12:29:46 2017
@@ -307,7 +307,7 @@ private:
   std::vector<unsigned> OpcodeOffset;
 
   void UpdateChains(SDNode *NodeToMatch, SDValue InputChain,
-                    const SmallVectorImpl<SDNode *> &ChainNodesMatched,
+                    SmallVectorImpl<SDNode *> &ChainNodesMatched,
                     bool isMorphNodeTo);
 };
 

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp?rev=293522&r1=293521&r2=293522&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp Mon Jan 30 12:29:46 2017
@@ -2308,7 +2308,7 @@ GetVBR(uint64_t Val, const unsigned char
 /// to use the new results.
 void SelectionDAGISel::UpdateChains(
     SDNode *NodeToMatch, SDValue InputChain,
-    const SmallVectorImpl<SDNode *> &ChainNodesMatched, bool isMorphNodeTo) {
+    SmallVectorImpl<SDNode *> &ChainNodesMatched, bool isMorphNodeTo) {
   SmallVector<SDNode*, 4> NowDeadNodes;
 
   // Now that all the normal results are replaced, we replace the chain and
@@ -2320,6 +2320,11 @@ void SelectionDAGISel::UpdateChains(
     // Replace all the chain results with the final chain we ended up with.
     for (unsigned i = 0, e = ChainNodesMatched.size(); i != e; ++i) {
       SDNode *ChainNode = ChainNodesMatched[i];
+      // If ChainNode is null, it's because we replaced it on a previous
+      // iteration and we cleared it out of the map. Just skip it.
+      if (!ChainNode)
+        continue;
+
       assert(ChainNode->getOpcode() != ISD::DELETED_NODE &&
              "Deleted node left in chain");
 
@@ -2332,6 +2337,11 @@ void SelectionDAGISel::UpdateChains(
       if (ChainVal.getValueType() == MVT::Glue)
         ChainVal = ChainVal.getValue(ChainVal->getNumValues()-2);
       assert(ChainVal.getValueType() == MVT::Other && "Not a chain?");
+      SelectionDAG::DAGNodeDeletedListener NDL(
+          *CurDAG, [&](SDNode *N, SDNode *E) {
+            std::replace(ChainNodesMatched.begin(), ChainNodesMatched.end(), N,
+                         static_cast<SDNode *>(nullptr));
+          });
       CurDAG->ReplaceAllUsesOfValueWith(ChainVal, InputChain);
 
       // If the node became dead and we haven't already seen it, delete it.

Added: llvm/trunk/test/CodeGen/SystemZ/pr31710.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/SystemZ/pr31710.ll?rev=293522&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/SystemZ/pr31710.ll (added)
+++ llvm/trunk/test/CodeGen/SystemZ/pr31710.ll Mon Jan 30 12:29:46 2017
@@ -0,0 +1,39 @@
+; RUN: llc < %s -mtriple=s390x-redhat-linux | FileCheck %s
+;
+; Triggers a path in SelectionDAG's UpdateChains where a node is
+; deleted but we try to read it later (pr31710), invoking UB in
+; release mode or hitting an assert if they're enabled.
+
+; CHECK: btldata:
+define void @btldata(i64* %u0, i32** %p0, i32** %p1, i32** %p3, i32** %p5, i32** %p7) {
+entry:
+  %x0 = load i32*, i32** %p0, align 8, !tbaa !0
+  store i64 0, i64* %u0, align 8, !tbaa !4
+  %x1 = load i32*, i32** %p1, align 8, !tbaa !0
+  %x2 = load i32, i32* %x1, align 4, !tbaa !6
+  %x2ext = sext i32 %x2 to i64
+  store i32 %x2, i32* %x1, align 4, !tbaa !6
+  %x3 = load i32*, i32** %p3, align 8, !tbaa !0
+  %ptr = getelementptr inbounds i32, i32* %x3, i64 %x2ext
+  %x4 = load i32, i32* %ptr, align 4, !tbaa !6
+  %x4inc = add nsw i32 %x4, 1
+  store i32 %x4inc, i32* %ptr, align 4, !tbaa !6
+  store i64 undef, i64* %u0, align 8, !tbaa !4
+  %x5 = load i32*, i32** %p5, align 8, !tbaa !0
+  %x6 = load i32, i32* %x5, align 4, !tbaa !6
+  store i32 %x6, i32* %x5, align 4, !tbaa !6
+  %x7 = load i32*, i32** %p7, align 8, !tbaa !0
+  %x8 = load i32, i32* %x7, align 4, !tbaa !6
+  %x8inc = add nsw i32 %x8, 1
+  store i32 %x8inc, i32* %x7, align 4, !tbaa !6
+  ret void
+}
+
+!0 = !{!1, !1, i64 0}
+!1 = !{!"any pointer", !2, i64 0}
+!2 = !{!"omnipotent char", !3, i64 0}
+!3 = !{!"Simple C/C++ TBAA"}
+!4 = !{!5, !5, i64 0}
+!5 = !{!"long", !2, i64 0}
+!6 = !{!7, !7, i64 0}
+!7 = !{!"int", !2, i64 0}