[globalisel][tablegen] Map ld and st to G_LOAD and G_STORE. NFC

Summary:
There is an important mismatch between ISD::LOAD and G_LOAD (and likewise for
ISD::STORE and G_STORE). In SelectionDAG, ISD::LOAD is a non-atomic load
and atomic loads are handled by a separate node. However, this is not true of
GlobalISel's G_LOAD. For G_LOAD, the MachineMemOperand indicates the atomicity
of the operation. As a result, this mapping must also add a predicate that
checks for non-atomic MachineMemOperands.

This is NFC since these nodes always have predicates in practice and are
therefore always rejected at the moment.

Depends on D37443

Reviewers: ab, qcolombet, t.p.northover, rovka, aditya_nandakumar

Reviewed By: qcolombet

Subscribers: kristof.beyls, llvm-commits, igorb

Differential Revision: https://reviews.llvm.org/D37445

llvm-svn: 315843

llvm/include/llvm/CodeGen/GlobalISel/InstructionSelector.h

@@ -107,6 +107,9 @@ enum {
   /// - InsnID - Instruction ID
   /// - The predicate to test
   GIM_CheckAPFloatImmPredicate,
+  /// Check a memory operation is non-atomic.
+  /// - InsnID - Instruction ID
+  GIM_CheckNonAtomic,
 
   /// Check the type for the specified operand
   /// - InsnID - Instruction ID

llvm/include/llvm/CodeGen/GlobalISel/InstructionSelectorImpl.h

@@ -209,6 +209,25 @@ bool InstructionSelector::executeMatchTable(
           return false;
       break;
     }
+    case GIM_CheckNonAtomic: {
+      int64_t InsnID = MatchTable[CurrentIdx++];
+      DEBUG(dbgs() << CurrentIdx << ": GIM_CheckNonAtomic(MIs[" << InsnID
+                   << "])\n");
+      assert(State.MIs[InsnID] != nullptr && "Used insn before defined");
+      assert((State.MIs[InsnID]->getOpcode() == TargetOpcode::G_LOAD ||
+              State.MIs[InsnID]->getOpcode() == TargetOpcode::G_STORE) &&
+             "Expected G_LOAD/G_STORE");
+
+      if (!State.MIs[InsnID]->hasOneMemOperand())
+        if (handleReject() == RejectAndGiveUp)
+          return false;
+
+      for (const auto &MMO : State.MIs[InsnID]->memoperands())
+        if (MMO->getOrdering() != AtomicOrdering::NotAtomic)
+          if (handleReject() == RejectAndGiveUp)
+            return false;
+      break;
+    }
 
     case GIM_CheckType: {
       int64_t InsnID = MatchTable[CurrentIdx++];

llvm/include/llvm/Target/GlobalISel/SelectionDAGCompat.td

@@ -23,6 +23,11 @@
 class GINodeEquiv<Instruction i, SDNode node> {
   Instruction I = i;
   SDNode Node = node;
+
+  // SelectionDAG has separate nodes for atomic and non-atomic memory operations
+  // (ISD::LOAD, ISD::ATOMIC_LOAD, ISD::STORE, ISD::ATOMIC_STORE) but GlobalISel
+  // stores this information in the MachineMemoryOperand.
+  bit CheckMMOIsNonAtomic = 0;
 }
 
 // These are defined in the same order as the G_* instructions.
@@ -72,6 +77,23 @@ def : GINodeEquiv<G_INTRINSIC_W_SIDE_EFFECTS, intrinsic_w_chain>;
 def : GINodeEquiv<G_BR, br>;
 def : GINodeEquiv<G_BSWAP, bswap>;
 
+// Broadly speaking G_LOAD is equivalent to ISD::LOAD but there are some
+// complications that tablegen must take care of. For example, Predicates such
+// as isSignExtLoad require that this is not a perfect 1:1 mapping since a
+// sign-extending load is (G_SEXT (G_LOAD x)) in GlobalISel. Additionally,
+// G_LOAD handles both atomic and non-atomic loads where as SelectionDAG had
+// separate nodes for them. This GINodeEquiv maps the non-atomic loads to
+// G_LOAD with a non-atomic MachineMemOperand.
+def : GINodeEquiv<G_LOAD, ld> { let CheckMMOIsNonAtomic = 1; }
+// Broadly speaking G_STORE is equivalent to ISD::STORE but there are some
+// complications that tablegen must take care of. For example, predicates such
+// as isTruncStore require that this is not a perfect 1:1 mapping since a
+// truncating store is (G_STORE (G_TRUNCATE x)) in GlobalISel. Additionally,
+// G_STORE handles both atomic and non-atomic stores where as SelectionDAG had
+// separate nodes for them. This GINodeEquiv maps the non-atomic stores to
+// G_STORE with a non-atomic MachineMemOperand.
+def : GINodeEquiv<G_STORE, st> { let CheckMMOIsNonAtomic = 1; }
+
 // Specifies the GlobalISel equivalents for SelectionDAG's ComplexPattern.
 // Should be used on defs that subclass GIComplexOperandMatcher<>.
 class GIComplexPatternEquiv<ComplexPattern seldag> {

llvm/utils/TableGen/GlobalISelEmitter.cpp

@@ -997,6 +997,7 @@ protected:
   enum PredicateKind {
     IPM_Opcode,
     IPM_ImmPredicate,
+    IPM_NonAtomicMMO,
   };
 
   PredicateKind Kind;
@@ -1125,6 +1126,24 @@ public:
   }
 };
 
+/// Generates code to check that a memory instruction has a non-atomic MachineMemoryOperand.
+class NonAtomicMMOPredicateMatcher : public InstructionPredicateMatcher {
+public:
+  NonAtomicMMOPredicateMatcher()
+      : InstructionPredicateMatcher(IPM_NonAtomicMMO) {}
+
+  static bool classof(const InstructionPredicateMatcher *P) {
+    return P->getKind() == IPM_NonAtomicMMO;
+  }
+
+  void emitPredicateOpcodes(MatchTable &Table, RuleMatcher &Rule,
+                            unsigned InsnVarID) const override {
+    Table << MatchTable::Opcode("GIM_CheckNonAtomic")
+          << MatchTable::Comment("MI") << MatchTable::IntValue(InsnVarID)
+          << MatchTable::LineBreak;
+  }
+};
+
 /// Generates code to check that a set of predicates and operands match for a
 /// particular instruction.
 ///
@@ -1991,9 +2010,11 @@ private:
   const CodeGenTarget &Target;
   CodeGenRegBank CGRegs;
 
-  /// Keep track of the equivalence between SDNodes and Instruction.
+  /// Keep track of the equivalence between SDNodes and Instruction by mapping
+  /// SDNodes to the GINodeEquiv mapping. We need to map to the GINodeEquiv to
+  /// check for attributes on the relation such as CheckMMOIsNonAtomic.
   /// This is defined using 'GINodeEquiv' in the target description.
-  DenseMap<Record *, const CodeGenInstruction *> NodeEquivs;
+  DenseMap<Record *, Record *> NodeEquivs;
 
   /// Keep track of the equivalence between ComplexPattern's and
   /// GIComplexOperandMatcher. Map entries are specified by subclassing
@@ -2004,7 +2025,7 @@ private:
   SubtargetFeatureInfoMap SubtargetFeatures;
 
   void gatherNodeEquivs();
-  const CodeGenInstruction *findNodeEquiv(Record *N) const;
+  Record *findNodeEquiv(Record *N) const;
 
   Error importRulePredicates(RuleMatcher &M, ArrayRef<Predicate> Predicates);
   Expected<InstructionMatcher &>
@@ -2041,8 +2062,7 @@ private:
 void GlobalISelEmitter::gatherNodeEquivs() {
   assert(NodeEquivs.empty());
   for (Record *Equiv : RK.getAllDerivedDefinitions("GINodeEquiv"))
-    NodeEquivs[Equiv->getValueAsDef("Node")] =
-        &Target.getInstruction(Equiv->getValueAsDef("I"));
+    NodeEquivs[Equiv->getValueAsDef("Node")] = Equiv;
 
   assert(ComplexPatternEquivs.empty());
   for (Record *Equiv : RK.getAllDerivedDefinitions("GIComplexPatternEquiv")) {
@@ -2053,7 +2073,7 @@ void GlobalISelEmitter::gatherNodeEquivs() {
  }
 }
 
-const CodeGenInstruction *GlobalISelEmitter::findNodeEquiv(Record *N) const {
+Record *GlobalISelEmitter::findNodeEquiv(Record *N) const {
   return NodeEquivs.lookup(N);
 }
 
@@ -2080,6 +2100,7 @@ Expected<InstructionMatcher &>
 GlobalISelEmitter::createAndImportSelDAGMatcher(InstructionMatcher &InsnMatcher,
                                                 const TreePatternNode *Src,
                                                 unsigned &TempOpIdx) const {
+  Record *SrcGIEquivOrNull = nullptr;
   const CodeGenInstruction *SrcGIOrNull = nullptr;
 
   // Start with the defined operands (i.e., the results of the root operator).
@@ -2095,14 +2116,14 @@ GlobalISelEmitter::createAndImportSelDAGMatcher(InstructionMatcher &InsnMatcher,
       return failedImport(
           "Unable to deduce gMIR opcode to handle Src (which is a leaf)");
   } else {
-    SrcGIOrNull = findNodeEquiv(Src->getOperator());
-    if (!SrcGIOrNull)
+    SrcGIEquivOrNull = findNodeEquiv(Src->getOperator());
+    if (!SrcGIEquivOrNull)
       return failedImport("Pattern operator lacks an equivalent Instruction" +
                           explainOperator(Src->getOperator()));
-    auto &SrcGI = *SrcGIOrNull;
+    SrcGIOrNull = &Target.getInstruction(SrcGIEquivOrNull->getValueAsDef("I"));
 
     // The operators look good: match the opcode
-    InsnMatcher.addPredicate<InstructionOpcodeMatcher>(&SrcGI);
+    InsnMatcher.addPredicate<InstructionOpcodeMatcher>(SrcGIOrNull);
   }
 
   unsigned OpIdx = 0;
@@ -2132,6 +2153,8 @@ GlobalISelEmitter::createAndImportSelDAGMatcher(InstructionMatcher &InsnMatcher,
     return failedImport("Src pattern child has predicate (" +
                         explainPredicates(Src) + ")");
   }
+  if (SrcGIEquivOrNull && SrcGIEquivOrNull->getValueAsBit("CheckMMOIsNonAtomic"))
+    InsnMatcher.addPredicate<NonAtomicMMOPredicateMatcher>();
 
   if (Src->isLeaf()) {
     Init *SrcInit = Src->getLeafValue();