Add a new function, ReplaceAllUsesOfValuesWith, which handles bulk

replacement of multiple values. This is slightly more efficient
than doing multiple ReplaceAllUsesOfValueWith calls, and theoretically
could be optimized even further. However, an important property of this
new function is that it handles the case where the source value set and
destination value set overlap. This makes it feasible for isel to use
SelectNodeTo in many very common cases, which is advantageous because
SelectNodeTo avoids a temporary node and it doesn't require CSEMap
updates for users of values that don't change position.

Revamp MorphNodeTo, which is what does all the work of SelectNodeTo, to
handle operand lists more efficiently, and to correctly handle a number
of corner cases to which its new wider use exposes it.

This commit also includes a change to the encoding of post-isel opcodes
in SDNodes; now instead of being sandwiched between the target-independent
pre-isel opcodes and the target-dependent pre-isel opcodes, post-isel
opcodes are now represented as negative values. This makes it possible
to test if an opcode is pre-isel or post-isel without having to know
the size of the current target's post-isel instruction set.

These changes speed up llc overall by 3% and reduce memory usage by 10%
on the InstructionCombining.cpp testcase with -fast and -regalloc=local.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53728 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 55 insertions, 42 deletions

diff --git a/utils/TableGen/DAGISelEmitter.cpp b/utils/TableGen/DAGISelEmitter.cpp
index bdb7fcf35a..2df9e88d57 100644
--- a/utils/TableGen/DAGISelEmitter.cpp
+++ b/utils/TableGen/DAGISelEmitter.cpp
@@ -1157,7 +1157,8 @@ public:
       if (!isRoot)
         Code += "), 0";
 
-      bool NeedReplace = false;
+      std::vector<std::string> ReplaceFroms;
+      std::vector<std::string> ReplaceTos;
       if (!isRoot) {
         NodeOps.push_back("Tmp" + utostr(ResNo));
       } else {
@@ -1176,33 +1177,35 @@ public:
 
       if (FoldedChains.size() > 0) {
         std::string Code;
-        for (unsigned j = 0, e = FoldedChains.size(); j < e; j++)
-          After.push_back("ReplaceUses(SDOperand(" +
-                          FoldedChains[j].first + ".Val, " + 
-                          utostr(FoldedChains[j].second) +
-                          "), SDOperand(ResNode, " +
-                          utostr(NumResults+NumDstRegs) + "));");
-        NeedReplace = true;
+        for (unsigned j = 0, e = FoldedChains.size(); j < e; j++) {
+          ReplaceFroms.push_back("SDOperand(" +
+                                 FoldedChains[j].first + ".Val, " +
+                                 utostr(FoldedChains[j].second) +
+                                 ")");
+          ReplaceTos.push_back("SDOperand(ResNode, " +
+                               utostr(NumResults+NumDstRegs) + ")");
+        }
       }
 
       if (NodeHasOutFlag) {
         if (FoldedFlag.first != "") {
-          After.push_back("ReplaceUses(SDOperand(" + FoldedFlag.first +
-                          ".Val, " +
-                          utostr(FoldedFlag.second) + "), InFlag);");
+          ReplaceFroms.push_back("SDOperand(" + FoldedFlag.first + ".Val, " +
+                                 utostr(FoldedFlag.second) + ")");
+          ReplaceTos.push_back("InFlag");
         } else {
           assert(NodeHasProperty(Pattern, SDNPOutFlag, CGP));
-          After.push_back("ReplaceUses(SDOperand(N.Val, " +
-                          utostr(NumPatResults + (unsigned)InputHasChain)
-                          +"), InFlag);");
+          ReplaceFroms.push_back("SDOperand(N.Val, " +
+                                 utostr(NumPatResults + (unsigned)InputHasChain)
+                                 + ")");
+          ReplaceTos.push_back("InFlag");
         }
-        NeedReplace = true;
       }
 
-      if (NeedReplace && InputHasChain) {
-        After.push_back("ReplaceUses(SDOperand(N.Val, " + 
-                        utostr(NumPatResults) + "), SDOperand(" + ChainName
-                        + ".Val, " + ChainName + ".ResNo" + "));");
+      if (!ReplaceFroms.empty() && InputHasChain) {
+        ReplaceFroms.push_back("SDOperand(N.Val, " +
+                               utostr(NumPatResults) + ")");
+        ReplaceTos.push_back("SDOperand(" + ChainName + ".Val, " +
+                             ChainName + ".ResNo" + ")");
         ChainAssignmentNeeded |= NodeHasChain;
       }
 
@@ -1211,13 +1214,15 @@ public:
         ;
       } else if (InputHasChain && !NodeHasChain) {
         // One of the inner node produces a chain.
-        if (NodeHasOutFlag)
-          After.push_back("ReplaceUses(SDOperand(N.Val, " +
-                          utostr(NumPatResults+1) +
-                          "), SDOperand(ResNode, N.ResNo-1));");
-        After.push_back("ReplaceUses(SDOperand(N.Val, " +
-                        utostr(NumPatResults) + "), " + ChainName + ");");
-        NeedReplace = true;
+        if (NodeHasOutFlag) {
+          ReplaceFroms.push_back("SDOperand(N.Val, " +
+                                 utostr(NumPatResults+1) +
+                                 ")");
+          ReplaceTos.push_back("SDOperand(ResNode, N.ResNo-1)");
+        }
+        ReplaceFroms.push_back("SDOperand(N.Val, " +
+                               utostr(NumPatResults) + ")");
+        ReplaceTos.push_back(ChainName);
       }
       }
 
@@ -1234,21 +1239,31 @@ public:
         After.push_front(ChainAssign);
       }
 
-      // Use getTargetNode or SelectNodeTo? The safe choice is getTargetNode,
-      // but SelectNodeTo can be faster.
-      //
-      // SelectNodeTo is not safe in a non-root context, or if there is any
-      // replacement of results needed.
+      if (ReplaceFroms.size() == 1) {
+        After.push_back("ReplaceUses(" + ReplaceFroms[0] + ", " +
+                        ReplaceTos[0] + ");");
+      } else if (!ReplaceFroms.empty()) {
+        After.push_back("const SDOperand Froms[] = {");
+        for (unsigned i = 0, e = ReplaceFroms.size(); i != e; ++i)
+          After.push_back("  " + ReplaceFroms[i] + (i + 1 != e ? "," : ""));
+        After.push_back("};");
+        After.push_back("const SDOperand Tos[] = {");
+        for (unsigned i = 0, e = ReplaceFroms.size(); i != e; ++i)
+          After.push_back("  " + ReplaceTos[i] + (i + 1 != e ? "," : ""));
+        After.push_back("};");
+        After.push_back("ReplaceUses(Froms, Tos, " +
+                        itostr(ReplaceFroms.size()) + ");");
+      }
+
+      // We prefer to use SelectNodeTo since it avoids allocation when
+      // possible and it avoids CSE map recalculation for the node's
+      // users, however it's tricky to use in a non-root context.
       //
-      // SelectNodeTo is not profitable if it would require a dynamically
-      // allocated operand list in a situation where getTargetNode would be
-      // able to reuse a co-allocated operand list (as in a unary, binary or
-      // ternary SDNode, for example).
+      // We also don't use if the pattern replacement is being used to
+      // jettison a chain result, since morphing the node in place
+      // would leave users of the chain dangling.
       //
-      if (!isRoot || NeedReplace ||
-          (!IsVariadic && AllOps.size() < 4 &&
-           Pattern->getNumChildren() + InputHasChain + NodeHasInFlag <
-             AllOps.size())) {
+      if (!isRoot || (InputHasChain && !NodeHasChain)) {
         Code = "CurDAG->getTargetNode(" + Code;
       } else {
         Code = "CurDAG->SelectNodeTo(N.Val, " + Code;
@@ -1952,9 +1967,7 @@ void DAGISelEmitter::EmitInstructionSelector(std::ostream &OS) {
 
   OS << "// The main instruction selector code.\n"
      << "SDNode *SelectCode(SDOperand N) {\n"
-     << "  if (N.getOpcode() >= ISD::BUILTIN_OP_END &&\n"
-     << "      N.getOpcode() < (ISD::BUILTIN_OP_END+" << InstNS
-     << "INSTRUCTION_LIST_END)) {\n"
+     << "  if (N.isMachineOpcode()) {\n"
      << "    return NULL;   // Already selected.\n"
      << "  }\n\n"
      << "  MVT::SimpleValueType NVT = N.Val->getValueType(0).getSimpleVT();\n"