[TableGen] Preserve order of output operands in DAGISelMatcherGen

Summary:
This fixes support in DAGISelMatcher backend for DAG nodes with multiple
result values. Previously the order of results in selected DAG nodes always
matched the order of results in ISel patterns. After the change the order of
results matches the order of operands in OutOperandList instead.

For example, given this definition from the attached test case:

  def INSTR : Instruction {
    let OutOperandList = (outs GPR:$r1, GPR:$r0);
    let InOperandList = (ins GPR:$t0, GPR:$t1);
    let Pattern = [(set i32:$r0, i32:$r1, (udivrem i32:$t0, i32:$t1))];
  }

the DAGISelMatcher backend currently produces a matcher that creates INSTR
nodes with the first result `$r0` and the second result `$r1`, contrary to the
order in the OutOperandList. The order of operands in OutOperandList does not
matter at all, which is unexpected (and unfortunate) because the order of
results of a DAG node does matters, perhaps a lot.

With this change, if the order in OutOperandList does not match the order in
Pattern, DAGISelMatcherGen emits CompleteMatch opcodes with the order of
results taken from OutOperandList. Backend writers can use it to express
result reorderings in TableGen.

If the order in OutOperandList matches the order in Pattern, the result of
DAGISelMatcherGen is unaffected.

Patch by Eugene Sharygin

Reviewers: andreadb, bjope, hfinkel, RKSimon, craig.topper

Reviewed By: craig.topper

Subscribers: nhaehnle, craig.topper, llvm-commits

Differential Revision: https://reviews.llvm.org/D55055

llvm-svn: 348326

test/TableGen/dag-isel-res-order.td

@@ -0,0 +1,22 @@
+// RUN: llvm-tblgen -gen-dag-isel -I %p/../../include %s | FileCheck %s
+
+include "llvm/Target/Target.td"
+
+def TestTargetInstrInfo : InstrInfo;
+
+def TestTarget : Target {
+  let InstructionSet = TestTargetInstrInfo;
+}
+
+def REG : Register<"REG">;
+def GPR : RegisterClass<"TestTarget", [i32], 32, (add REG)>;
+
+// CHECK-LABEL: OPC_CheckOpcode, TARGET_VAL(ISD::UDIVREM)
+// CHECK: OPC_EmitNode2, TARGET_VAL(::INSTR)
+// CHECK: Results = #2 #3
+// CHECK: OPC_CompleteMatch, 2, 3, 2
+def INSTR : Instruction {
+  let OutOperandList = (outs GPR:$r1, GPR:$r0);
+  let InOperandList = (ins GPR:$t0, GPR:$t1);
+  let Pattern = [(set i32:$r0, i32:$r1, (udivrem i32:$t0, i32:$t1))];
+}

utils/TableGen/CodeGenDAGPatterns.cpp

@@ -15,6 +15,7 @@
 #include "CodeGenDAGPatterns.h"
 #include "llvm/ADT/BitVector.h"
 #include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/SmallString.h"
@@ -27,6 +28,7 @@
 #include "llvm/TableGen/Record.h"
 #include <algorithm>
 #include <cstdio>
+#include <iterator>
 #include <set>
 using namespace llvm;
 
@@ -1940,6 +1942,8 @@ void TreePatternNode::InlinePatternFragments(
       R->setTransformFn(getTransformFn());
       for (unsigned i = 0, e = getNumTypes(); i != e; ++i)
         R->setType(i, getExtType(i));
+      for (unsigned i = 0, e = getNumResults(); i != e; ++i)
+        R->setResultIndex(i, getResultIndex(i));
 
       // Register alternative.
       OutAlternatives.push_back(R);
@@ -3207,7 +3211,8 @@ static bool HandleUse(TreePattern &I, TreePatternNodePtr Pat,
 void CodeGenDAGPatterns::FindPatternInputsAndOutputs(
     TreePattern &I, TreePatternNodePtr Pat,
     std::map<std::string, TreePatternNodePtr> &InstInputs,
-    std::map<std::string, TreePatternNodePtr> &InstResults,
+    MapVector<std::string, TreePatternNodePtr, std::map<std::string, unsigned>>
+        &InstResults,
     std::vector<Record *> &InstImpResults) {
 
   // The instruction pattern still has unresolved fragments.  For *named*
@@ -3527,7 +3532,8 @@ void CodeGenDAGPatterns::parseInstructionPattern(
 
   // InstResults - Keep track of all the virtual registers that are 'set'
   // in the instruction, including what reg class they are.
-  std::map<std::string, TreePatternNodePtr> InstResults;
+  MapVector<std::string, TreePatternNodePtr, std::map<std::string, unsigned>>
+      InstResults;
 
   std::vector<Record*> InstImpResults;
 
@@ -3564,19 +3570,28 @@ void CodeGenDAGPatterns::parseInstructionPattern(
 
   // Check that all of the results occur first in the list.
   std::vector<Record*> Results;
+  std::vector<unsigned> ResultIndices;
   SmallVector<TreePatternNodePtr, 2> ResNodes;
   for (unsigned i = 0; i != NumResults; ++i) {
-    if (i == CGI.Operands.size())
-      I.error("'" + InstResults.begin()->first +
-               "' set but does not appear in operand list!");
+    if (i == CGI.Operands.size()) {
+      const std::string &OpName =
+          std::find_if(InstResults.begin(), InstResults.end(),
+                       [](const std::pair<std::string, TreePatternNodePtr> &P) {
+                         return P.second;
+                       })
+              ->first;
+
+      I.error("'" + OpName + "' set but does not appear in operand list!");
+    }
+
     const std::string &OpName = CGI.Operands[i].Name;
 
     // Check that it exists in InstResults.
-    TreePatternNodePtr RNode = InstResults[OpName];
-    if (!RNode)
+    auto InstResultIter = InstResults.find(OpName);
+    if (InstResultIter == InstResults.end() || !InstResultIter->second)
       I.error("Operand $" + OpName + " does not exist in operand list!");
 
-
+    TreePatternNodePtr RNode = InstResultIter->second;
     Record *R = cast<DefInit>(RNode->getLeafValue())->getDef();
     ResNodes.push_back(std::move(RNode));
     if (!R)
@@ -3589,8 +3604,11 @@ void CodeGenDAGPatterns::parseInstructionPattern(
     // Remember the return type.
     Results.push_back(CGI.Operands[i].Rec);
 
+    // Remember the result index.
+    ResultIndices.push_back(std::distance(InstResults.begin(), InstResultIter));
+
     // Okay, this one checks out.
-    InstResults.erase(OpName);
+    InstResultIter->second = nullptr;
   }
 
   // Loop over the inputs next.
@@ -3654,6 +3672,7 @@ void CodeGenDAGPatterns::parseInstructionPattern(
   for (unsigned i = 0; i != NumResults; ++i) {
     assert(ResNodes[i]->getNumTypes() == 1 && "FIXME: Unhandled");
     ResultPattern->setType(i, ResNodes[i]->getExtType(0));
+    ResultPattern->setResultIndex(i, ResultIndices[i]);
   }
 
   // FIXME: Assume only the first tree is the pattern. The others are clobber
@@ -4113,7 +4132,8 @@ void CodeGenDAGPatterns::ParsePatterns() {
 
     // Validate that the input pattern is correct.
     std::map<std::string, TreePatternNodePtr> InstInputs;
-    std::map<std::string, TreePatternNodePtr> InstResults;
+    MapVector<std::string, TreePatternNodePtr, std::map<std::string, unsigned>>
+        InstResults;
     std::vector<Record*> InstImpResults;
     for (unsigned j = 0, ee = Pattern.getNumTrees(); j != ee; ++j)
       FindPatternInputsAndOutputs(Pattern, Pattern.getTree(j), InstInputs,

utils/TableGen/CodeGenDAGPatterns.h

@@ -19,6 +19,7 @@
 #include "CodeGenIntrinsics.h"
 #include "CodeGenTarget.h"
 #include "SDNodeProperties.h"
+#include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringSet.h"
@@ -28,6 +29,7 @@
 #include <array>
 #include <functional>
 #include <map>
+#include <numeric>
 #include <set>
 #include <vector>
 
@@ -620,6 +622,9 @@ class TreePatternNode {
   /// each is a single concrete type.
   std::vector<TypeSetByHwMode> Types;
 
+  /// The index of each result in results of the pattern.
+  std::vector<unsigned> ResultPerm;
+
   /// Operator - The Record for the operator if this is an interior node (not
   /// a leaf).
   Record *Operator;
@@ -650,10 +655,14 @@ public:
       : Operator(Op), Val(nullptr), TransformFn(nullptr),
         Children(std::move(Ch)) {
     Types.resize(NumResults);
+    ResultPerm.resize(NumResults);
+    std::iota(ResultPerm.begin(), ResultPerm.end(), 0);
   }
   TreePatternNode(Init *val, unsigned NumResults)    // leaf ctor
     : Operator(nullptr), Val(val), TransformFn(nullptr) {
     Types.resize(NumResults);
+    ResultPerm.resize(NumResults);
+    std::iota(ResultPerm.begin(), ResultPerm.end(), 0);
   }
 
   bool hasName() const { return !Name.empty(); }
@@ -694,6 +703,10 @@ public:
     return Types[ResNo].empty();
   }
 
+  unsigned getNumResults() const { return ResultPerm.size(); }
+  unsigned getResultIndex(unsigned ResNo) const { return ResultPerm[ResNo]; }
+  void setResultIndex(unsigned ResNo, unsigned RI) { ResultPerm[ResNo] = RI; }
+
   Init *getLeafValue() const { assert(isLeaf()); return Val; }
   Record *getOperator() const { assert(!isLeaf()); return Operator; }
 
@@ -1281,7 +1294,8 @@ private:
   void FindPatternInputsAndOutputs(
       TreePattern &I, TreePatternNodePtr Pat,
       std::map<std::string, TreePatternNodePtr> &InstInputs,
-      std::map<std::string, TreePatternNodePtr> &InstResults,
+      MapVector<std::string, TreePatternNodePtr,
+                std::map<std::string, unsigned>> &InstResults,
       std::vector<Record *> &InstImpResults);
 };
 

utils/TableGen/DAGISelMatcherGen.cpp

@@ -1000,9 +1000,16 @@ void MatcherGen::EmitResultCode() {
   }
 
   assert(Ops.size() >= NumSrcResults && "Didn't provide enough results");
-  Ops.resize(NumSrcResults);
+  SmallVector<unsigned, 8> Results(Ops);
 
-  AddMatcher(new CompleteMatchMatcher(Ops, Pattern));
+  // Apply result permutation.
+  for (unsigned ResNo = 0; ResNo < Pattern.getDstPattern()->getNumResults();
+       ++ResNo) {
+    Results[ResNo] = Ops[Pattern.getDstPattern()->getResultIndex(ResNo)];
+  }
+
+  Results.resize(NumSrcResults);
+  AddMatcher(new CompleteMatchMatcher(Results, Pattern));
 }