Another folding problem: if a node r/w chain or flag, don't fold it if it

has already been selected. The number of use check is not strong enough since
a node can be replaced with newly created target node. e.g. If the original
node has two uses, when it is selected for one of the uses it is replaced with
another. Each node now has a single use but isel still should not fold it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@25651 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/utils/TableGen/DAGISelEmitter.cpp b/utils/TableGen/DAGISelEmitter.cpp
index 7b00b4e4dc6d83e7392eeebc683c29646e6a563d..2ce87cf422e7342c560a53a197d4a3e865775c5f 100644 (file)
--- a/utils/TableGen/DAGISelEmitter.cpp
+++ b/utils/TableGen/DAGISelEmitter.cpp
@@ -1909,7 +1909,8 @@ public:
     unsigned OpNo = 0;
     bool NodeHasChain = NodeHasProperty(N, SDNodeInfo::SDNPHasChain, ISE);
     bool HasChain = PatternHasProperty(N, SDNodeInfo::SDNPHasChain, ISE);
-    bool EmittedCheck = false;
+    bool EmittedUseCheck = false;
+    bool EmittedSlctedCheck = false;
     if (HasChain) {
       if (NodeHasChain)
         OpNo = 1;
@@ -1917,7 +1918,14 @@ public:
         const SDNodeInfo &CInfo = ISE.getSDNodeInfo(N->getOperator());
         OS << "      if (!" << RootName << ".hasOneUse()) goto P"
            << PatternNo << "Fail;   // Multiple uses of actual result?\n";
-        EmittedCheck = true;
+        EmittedUseCheck = true;
+        // hasOneUse() check is not strong enough. If the original node has
+        // already been selected, it may have been replaced with another.
+        for (unsigned j = 0; j < CInfo.getNumResults(); j++)
+          OS << "      if (CodeGenMap.count(" << RootName
+             << ".getValue(" << j << "))) goto P"
+             << PatternNo << "Fail;   // Already selected?\n";
+        EmittedSlctedCheck = true;
         if (NodeHasChain)
           OS << "      if (CodeGenMap.count(" << RootName
              << ".getValue(" << CInfo.getNumResults() << "))) goto P"
@@ -1933,15 +1941,22 @@ public:
     // FIXME: we really need to separate the concepts of flag and "glue". Those
     // real flag results, e.g. X86CMP output, can have multiple uses.
     // FIXME: If the incoming flag is optional. Then it is ok to fold it.
-    if (!EmittedCheck &&
+    if (!isRoot &&
         (PatternHasProperty(N, SDNodeInfo::SDNPInFlag, ISE) ||
          PatternHasProperty(N, SDNodeInfo::SDNPOptInFlag, ISE) ||
          PatternHasProperty(N, SDNodeInfo::SDNPOutFlag, ISE))) {
-      if (!isRoot) {
-        const SDNodeInfo &CInfo = ISE.getSDNodeInfo(N->getOperator());
+      const SDNodeInfo &CInfo = ISE.getSDNodeInfo(N->getOperator());
+      if (!EmittedUseCheck) {
         OS << "      if (!" << RootName << ".hasOneUse()) goto P"
            << PatternNo << "Fail;   // Multiple uses of actual result?\n";
       }
+      if (!EmittedSlctedCheck)
+        // hasOneUse() check is not strong enough. If the original node has
+        // already been selected, it may have been replaced with another.
+        for (unsigned j = 0; j < CInfo.getNumResults(); j++)
+          OS << "      if (CodeGenMap.count(" << RootName
+             << ".getValue(" << j << "))) goto P"
+             << PatternNo << "Fail;   // Already selected?\n";
     }
 
     for (unsigned i = 0, e = N->getNumChildren(); i != e; ++i, ++OpNo) {