From e9025f1f3ba4447d5314895a28e36e414490763c Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Thu, 26 Jan 2006 19:13:45 +0000
Subject: [PATCH] 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.

llvm-svn: 25651
---
 llvm/utils/TableGen/DAGISelEmitter.cpp | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/llvm/utils/TableGen/DAGISelEmitter.cpp b/llvm/utils/TableGen/DAGISelEmitter.cpp
index 7b00b4e4dc6d..2ce87cf422e7 100644
--- a/llvm/utils/TableGen/DAGISelEmitter.cpp
+++ b/llvm/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) {