From 94bd553eb8429dce48e64380a67d814cbc8f2ebd Mon Sep 17 00:00:00 2001
From: Chandler Carruth <chandlerc@gmail.com>
Date: Fri, 25 Jul 2014 07:23:23 +0000
Subject: [PATCH] [SDAG] Start plumbing an assert into SDValues that we don't
 form one with a result number outside the range of results for the node.

I don't know how we managed to not really check this very basic
invariant for so long, but the code is *very* broken at this point.
I have over 270 test failures with the assert enabled. I'm committing it
disabled so that others can join in the cleanup effort and reproduce the
issues. I've also included one of the obvious fixes that I already
found. More fixes to come.

llvm-svn: 213926
---
 llvm/include/llvm/CodeGen/SelectionDAGNodes.h | 24 +++++++++++++++++++++---
 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp |  2 +-
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/llvm/include/llvm/CodeGen/SelectionDAGNodes.h b/llvm/include/llvm/CodeGen/SelectionDAGNodes.h
index 0aa96cd..f93f8e4 100644
--- a/llvm/include/llvm/CodeGen/SelectionDAGNodes.h
+++ b/llvm/include/llvm/CodeGen/SelectionDAGNodes.h
@@ -117,11 +117,13 @@ namespace ISD {
 /// of information is represented with the SDValue value type.
 ///
 class SDValue {
+  friend struct DenseMapInfo<SDValue>;
+
   SDNode *Node;       // The node defining the value we are using.
   unsigned ResNo;     // Which return value of the node we are using.
 public:
   SDValue() : Node(nullptr), ResNo(0) {}
-  SDValue(SDNode *node, unsigned resno) : Node(node), ResNo(resno) {}
+  SDValue(SDNode *node, unsigned resno);
 
   /// get the index which selects a specific result in the SDNode
   unsigned getResNo() const { return ResNo; }
@@ -208,10 +210,14 @@ public:
 
 template<> struct DenseMapInfo<SDValue> {
   static inline SDValue getEmptyKey() {
-    return SDValue((SDNode*)-1, -1U);
+    SDValue V;
+    V.ResNo = -1U;
+    return V;
   }
   static inline SDValue getTombstoneKey() {
-    return SDValue((SDNode*)-1, 0);
+    SDValue V;
+    V.ResNo = -2U;
+    return V;
   }
   static unsigned getHashValue(const SDValue &Val) {
     return ((unsigned)((uintptr_t)Val.getNode() >> 4) ^
@@ -877,6 +883,18 @@ public:
 
 // Define inline functions from the SDValue class.
 
+inline SDValue::SDValue(SDNode *node, unsigned resno)
+    : Node(node), ResNo(resno) {
+// This is currently disabled because it fires pretty widely, but I wanted to
+// commit it so others could help reproduce and aid in the cleanup. It will get
+// enabled ASAP.
+#if 0
+  assert((!Node || ResNo < Node->getNumValues()) &&
+         "Invalid result number for the given node!");
+#endif
+  assert(ResNo < -2U && "Cannot use result numbers reserved for DenseMaps.");
+}
+
 inline unsigned SDValue::getOpcode() const {
   return Node->getOpcode();
 }
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 379ea7f..a9ba5b8 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -9088,7 +9088,7 @@ bool DAGCombiner::MergeConsecutiveStores(StoreSDNode* St) {
     return false;
 
   // Only look at ends of store sequences.
-  SDValue Chain = SDValue(St, 1);
+  SDValue Chain = SDValue(St, 0);
   if (Chain->hasOneUse() && Chain->use_begin()->getOpcode() == ISD::STORE)
     return false;
 
-- 
2.7.4