From: Evan Cheng <evan.cheng@apple.com>
Date: Thu, 12 Oct 2006 02:08:53 +0000 (+0000)
Subject: Prior load folding check on chain operand was too strict. It requires the
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=4326ef582bceb8841f36623d98a98ee879642f2f;p=oota-llvm.git

Prior load folding check on chain operand was too strict. It requires the
chain operand to point to the load being folded. Now we relax this, traversing
up the chain, if it doesn't reach the load, then it's ok. We will create a
TokenFactor (of all the chain operands and the load's chain) to capture all
the control flow dependencies.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30897 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/utils/TableGen/DAGISelEmitter.cpp b/utils/TableGen/DAGISelEmitter.cpp
index 9deb43514bf..5221fe025bf 100644
--- a/utils/TableGen/DAGISelEmitter.cpp
+++ b/utils/TableGen/DAGISelEmitter.cpp
@@ -2138,6 +2138,8 @@ private:
   std::map<std::string, Record*> OperatorMap;
   // Names of all the folded nodes which produce chains.
   std::vector<std::pair<std::string, unsigned> > FoldedChains;
+  // Original input chain(s).
+  std::vector<std::pair<std::string, std::string> > OrigChains;
   std::set<std::string> Duplicates;
 
   /// GeneratedCode - This is the buffer that we emit code to.  The first int
@@ -2294,9 +2296,12 @@ public:
       }
 
       if (NodeHasChain) {
-        if (FoundChain)
-          emitCheck("Chain.Val == " + RootName + ".Val");
-        else
+        if (FoundChain) {
+          emitCheck("(" + ChainName + ".Val == " + RootName + ".Val || "
+                    "IsChainCompatible(" + ChainName + ".Val, " +
+                    RootName + ".Val))");
+          OrigChains.push_back(std::make_pair(ChainName, RootName));
+        } else
           FoundChain = true;
         ChainName = "Chain" + ChainSuffix;
         emitInit("SDOperand " + ChainName + " = " + RootName +
@@ -2665,6 +2670,26 @@ public:
           PatResults++;
       }
 
+      if (OrigChains.size() > 0) {
+        // The original input chain is being ignored. If it is not just
+        // pointing to the op that's being folded, we should create a
+        // TokenFactor with it and the chain of the folded op as the new chain.
+        // We could potentially be doing multiple levels of folding, in that
+        // case, the TokenFactor can have more operands.
+        emitCode("SmallVector<SDOperand, 8> InChains;");
+        for (unsigned i = 0, e = OrigChains.size(); i < e; ++i) {
+          emitCode("if (" + OrigChains[i].first + ".Val != " +
+                   OrigChains[i].second + ".Val) {");
+          emitCode("  AddToISelQueue(" + OrigChains[i].first + ");");
+          emitCode("  InChains.push_back(" + OrigChains[i].first + ");");
+          emitCode("}");
+        }
+        emitCode("AddToISelQueue(" + ChainName + ");");
+        emitCode("InChains.push_back(" + ChainName + ");");
+        emitCode(ChainName + " = CurDAG->getNode(ISD::TokenFactor, MVT::Other, "
+                 "&InChains[0], InChains.size());");
+      }
+
       std::vector<std::string> AllOps;
       for (unsigned i = 0, e = N->getNumChildren(); i != e; ++i) {
         std::vector<std::string> Ops = EmitResultCode(N->getChild(i),
@@ -3647,6 +3672,21 @@ void DAGISelEmitter::run(std::ostream &OS) {
   OS << "/// Dummy parameter to ReplaceAllUsesOfValueWith().\n"
      << "std::vector<SDNode*> ISelKilled;\n\n";
 
+  OS << "/// IsChainCompatible - Returns true if Chain is Op or Chain does\n";
+  OS << "/// not reach Op.\n";
+  OS << "static bool IsChainCompatible(SDNode *Chain, SDNode *Op) {\n";
+  OS << "  if (Chain->getOpcode() == ISD::EntryToken)\n";
+  OS << "    return true;\n";
+  OS << "  else if (Chain->getOpcode() == ISD::TokenFactor)\n";
+  OS << "    return false;\n";
+  OS << "  else if (Chain->getNumOperands() > 0) {\n";
+  OS << "    SDOperand C0 = Chain->getOperand(0);\n";
+  OS << "    if (C0.getValueType() == MVT::Other)\n";
+  OS << "      return C0.Val != Op && IsChainCompatible(C0.Val, Op);\n";
+  OS << "  }\n";
+  OS << "  return true;\n";
+  OS << "}\n";
+
   OS << "/// Sorting functions for the selection queue.\n"
      << "struct isel_sort : public std::binary_function"
      << "<SDNode*, SDNode*, bool> {\n"