Re-commit with some instrumentation: [globalisel][tablegen] Support z…

…ero-instruction emission.

Summary:
Support the case where an operand of a pattern is also the whole of the
result pattern. In this case the original result and all its uses must be
replaced by the operand. However, register class restrictions can require
a COPY. This patch handles both cases by always emitting the copy and
leaving it for the register allocator to optimize.

The previous commit failed on the windows bots and this one is likely to fail
on those same bots. However, the added instrumentation should reveal a particular
isHigherPriorityThan() evaluation which I'm expecting to expose that
these machines are weighing priority of two rules differently from the
non-windows machines.

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

Subscribers: javed.absar, kristof.beyls, igorb, llvm-commits

Differential Revision: https://reviews.llvm.org/D36084

llvm-svn: 310919

llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp

@@ -1163,9 +1163,19 @@ bool AArch64InstructionSelector::select(MachineInstr &I) const {
 
 
   case TargetOpcode::G_INTTOPTR:
-  case TargetOpcode::G_BITCAST:
+    // The importer is currently unable to import pointer types since they
+    // didn't exist in SelectionDAG.
     return selectCopy(I, TII, MRI, TRI, RBI);
 
+  case TargetOpcode::G_BITCAST:
+    // Imported SelectionDAG rules can handle every bitcast except those that
+    // bitcast from a type to the same type. Ideally, these shouldn't occur
+    // but we might not run an optimizer that deletes them.
+    if (MRI.getType(I.getOperand(0).getReg()) ==
+        MRI.getType(I.getOperand(1).getReg()))
+      return selectCopy(I, TII, MRI, TRI, RBI);
+    return false;
+
   case TargetOpcode::G_FPEXT: {
     if (MRI.getType(I.getOperand(0).getReg()) != LLT::scalar(64)) {
       DEBUG(dbgs() << "G_FPEXT to type " << Ty

llvm/test/CodeGen/AArch64/GlobalISel/select-bitcast.mir

@@ -11,6 +11,8 @@
   define void @bitcast_s64_fpr() { ret void }
   define void @bitcast_s64_gpr_fpr() { ret void }
   define void @bitcast_s64_fpr_gpr() { ret void }
+  define void @bitcast_s64_v2f32_fpr() { ret void }
+  define void @bitcast_s64_v8i8_fpr() { ret void }
 ...
 
 ---
@@ -210,3 +212,53 @@ body:             |
     %1(s64) = G_BITCAST %0
     %x0 = COPY %1(s64)
 ...
+
+---
+# CHECK-LABEL: name: bitcast_s64_v2f32_fpr
+name:            bitcast_s64_v2f32_fpr
+legalized:       true
+regBankSelected: true
+
+# CHECK:      registers:
+# CHECK-NEXT:  - { id: 0, class: fpr64, preferred-register: '' }
+# CHECK-NEXT:  - { id: 1, class: fpr64, preferred-register: '' }
+registers:
+  - { id: 0, class: fpr }
+  - { id: 1, class: fpr }
+
+# CHECK:  body:
+# CHECK:    %0 = COPY %d0
+# CHECK:    %1 = COPY %0
+body:             |
+  bb.0:
+    liveins: %d0
+
+    %0(s64) = COPY %d0
+    %1(<2 x s32>) = G_BITCAST %0
+    %x0 = COPY %1(<2 x s32>)
+...
+
+---
+# CHECK-LABEL: name: bitcast_s64_v8i8_fpr
+name:            bitcast_s64_v8i8_fpr
+legalized:       true
+regBankSelected: true
+
+# CHECK:      registers:
+# CHECK-NEXT:  - { id: 0, class: fpr64, preferred-register: '' }
+# CHECK-NEXT:  - { id: 1, class: fpr64, preferred-register: '' }
+registers:
+  - { id: 0, class: fpr }
+  - { id: 1, class: fpr }
+
+# CHECK:  body:
+# CHECK:    %0 = COPY %d0
+# CHECK:    %1 = COPY %0
+body:             |
+  bb.0:
+    liveins: %d0
+
+    %0(s64) = COPY %d0
+    %1(<8 x s8>) = G_BITCAST %0
+    %x0 = COPY %1(<8 x s8>)
+...

llvm/test/TableGen/GlobalISelEmitter.td

@@ -83,6 +83,13 @@ def HasC : Predicate<"Subtarget->hasC()"> { let RecomputePerFunction = 1; }
 // CHECK-NEXT:    return Features;
 // CHECK-NEXT:  }
 
+// CHECK-LABEL: enum {
+// CHECK-NEXT:    GILLT_s32,
+// CHECK-NEXT:  }
+// CHECK-NEXT:  const static LLT TypeObjects[] = {
+// CHECK-NEXT:    LLT::scalar(32),
+// CHECK-NEXT:  };
+
 // CHECK: bool MyTargetInstructionSelector::selectImpl(MachineInstr &I) const {
 // CHECK-NEXT: MachineFunction &MF = *I.getParent()->getParent();
 // CHECK-NEXT: MachineRegisterInfo &MRI = MF.getRegInfo();

llvm/utils/TableGen/GlobalISelEmitter.cpp

@@ -110,30 +110,28 @@ class LLTCodeGen {
   const LLT &get() const { return Ty; }
 
   /// This ordering is used for std::unique() and std::sort(). There's no
-  /// particular logic behind the order.
+  /// particular logic behind the order but either A < B or B < A must be
+  /// true if A != B.
   bool operator<(const LLTCodeGen &Other) const {
+    if (Ty.isValid() != Other.Ty.isValid())
+      return Ty.isValid() < Other.Ty.isValid();
     if (!Ty.isValid())
-      return Other.Ty.isValid();
-    if (Ty.isScalar()) {
-      if (!Other.Ty.isValid())
-        return false;
-      if (Other.Ty.isScalar())
-        return Ty.getSizeInBits() < Other.Ty.getSizeInBits();
       return false;
-    }
-    if (Ty.isVector()) {
-      if (!Other.Ty.isValid() || Other.Ty.isScalar())
-        return false;
-      if (Other.Ty.isVector()) {
-        if (Ty.getNumElements() < Other.Ty.getNumElements())
-          return true;
-        if (Ty.getNumElements() > Other.Ty.getNumElements())
-          return false;
-        return Ty.getSizeInBits() < Other.Ty.getSizeInBits();
-      }
-      return false;
-    }
-    llvm_unreachable("Unhandled LLT");
+
+    if (Ty.isVector() != Other.Ty.isVector())
+      return Ty.isVector() < Other.Ty.isVector();
+    if (Ty.isScalar() != Other.Ty.isScalar())
+      return Ty.isScalar() < Other.Ty.isScalar();
+    if (Ty.isPointer() != Other.Ty.isPointer())
+      return Ty.isPointer() < Other.Ty.isPointer();
+
+    if (Ty.isPointer() && Ty.getAddressSpace() != Other.Ty.getAddressSpace())
+      return Ty.getAddressSpace() < Other.Ty.getAddressSpace();
+
+    if (Ty.isVector() && Ty.getNumElements() != Other.Ty.getNumElements())
+      return Ty.getNumElements() < Other.Ty.getNumElements();
+
+    return Ty.getSizeInBits() < Other.Ty.getSizeInBits();
   }
 };
 
@@ -182,14 +180,6 @@ static Error failedImport(const Twine &Reason) {
 static Error isTrivialOperatorNode(const TreePatternNode *N) {
   std::string Explanation = "";
   std::string Separator = "";
-  if (N->isLeaf()) {
-    if (isa<IntInit>(N->getLeafValue()))
-      return Error::success();
-
-    Explanation = "Is a leaf";
-    Separator = ", ";
-  }
-
   if (N->hasAnyPredicate()) {
     Explanation = Separator + "Has a predicate (" + explainPredicates(N) + ")";
     Separator = ", ";
@@ -200,7 +190,7 @@ static Error isTrivialOperatorNode(const TreePatternNode *N) {
     Separator = ", ";
   }
 
-  if (!N->isLeaf() && !N->hasAnyPredicate() && !N->getTransformFn())
+  if (!N->hasAnyPredicate() && !N->getTransformFn())
     return Error::success();
 
   return failedImport(Explanation);
@@ -458,7 +448,9 @@ class RuleMatcher {
 
   /// A list of actions that need to be taken when all predicates in this rule
   /// have succeeded.
+public:
   std::vector<std::unique_ptr<MatchAction>> Actions;
+protected:
 
   typedef std::map<const InstructionMatcher *, unsigned>
       DefinedInsnVariablesMap;
@@ -634,8 +626,12 @@ class LLTOperandMatcher : public OperandPredicateMatcher {
   LLTCodeGen Ty;
 
 public:
+  static std::set<LLTCodeGen> KnownTypes;
+
   LLTOperandMatcher(const LLTCodeGen &Ty)
-      : OperandPredicateMatcher(OPM_LLT), Ty(Ty) {}
+      : OperandPredicateMatcher(OPM_LLT), Ty(Ty) {
+    KnownTypes.insert(Ty);
+  }
 
   static bool classof(const OperandPredicateMatcher *P) {
     return P->getKind() == OPM_LLT;
@@ -651,6 +647,8 @@ class LLTOperandMatcher : public OperandPredicateMatcher {
   }
 };
 
+std::set<LLTCodeGen> LLTOperandMatcher::KnownTypes;
+
 /// Generates code to check that an operand is a particular target constant.
 class ComplexPatternOperandMatcher : public OperandPredicateMatcher {
 protected:
@@ -1436,7 +1434,9 @@ class DebugCommentAction : public MatchAction {
 class BuildMIAction : public MatchAction {
 private:
   unsigned InsnID;
+public:
   const CodeGenInstruction *I;
+private:
   const InstructionMatcher &Matched;
   std::vector<std::unique_ptr<OperandRenderer>> OperandRenderers;
 
@@ -2287,8 +2287,42 @@ Expected<RuleMatcher> GlobalISelEmitter::runOnPattern(const PatternToMatch &P) {
     return failedImport("Src pattern root isn't a trivial operator (" +
                         toString(std::move(Err)) + ")");
 
-  if (Dst->isLeaf())
+  InstructionMatcher &InsnMatcherTemp = M.addInstructionMatcher(Src->getName());
+  unsigned TempOpIdx = 0;
+  auto InsnMatcherOrError =
+      createAndImportSelDAGMatcher(InsnMatcherTemp, Src, TempOpIdx);
+  if (auto Error = InsnMatcherOrError.takeError())
+    return std::move(Error);
+  InstructionMatcher &InsnMatcher = InsnMatcherOrError.get();
+
+  if (Dst->isLeaf()) {
+    Record *RCDef = getInitValueAsRegClass(Dst->getLeafValue());
+
+    const CodeGenRegisterClass &RC = Target.getRegisterClass(RCDef);
+    if (RCDef) {
+      // We need to replace the def and all its uses with the specified
+      // operand. However, we must also insert COPY's wherever needed.
+      // For now, emit a copy and let the register allocator clean up.
+      auto &DstI = Target.getInstruction(RK.getDef("COPY"));
+      const auto &DstIOperand = DstI.Operands[0];
+
+      OperandMatcher &OM0 = InsnMatcher.getOperand(0);
+      OM0.setSymbolicName(DstIOperand.Name);
+      OM0.addPredicate<RegisterBankOperandMatcher>(RC);
+
+      auto &DstMIBuilder = M.addAction<BuildMIAction>(0, &DstI, InsnMatcher);
+      DstMIBuilder.addRenderer<CopyRenderer>(0, InsnMatcher, DstIOperand.Name);
+      DstMIBuilder.addRenderer<CopyRenderer>(0, InsnMatcher, Dst->getName());
+      M.addAction<ConstrainOperandToRegClassAction>(0, 0, RC);
+
+      // We're done with this pattern!  It's eligible for GISel emission; return
+      // it.
+      ++NumPatternImported;
+      return std::move(M);
+    }
+
     return failedImport("Dst pattern root isn't a known leaf");
+  }
 
   // Start with the defined operands (i.e., the results of the root operator).
   Record *DstOp = Dst->getOperator();
@@ -2301,14 +2335,6 @@ Expected<RuleMatcher> GlobalISelEmitter::runOnPattern(const PatternToMatch &P) {
                         to_string(Src->getExtTypes().size()) + " def(s) vs " +
                         to_string(DstI.Operands.NumDefs) + " def(s))");
 
-  InstructionMatcher &InsnMatcherTemp = M.addInstructionMatcher(Src->getName());
-  unsigned TempOpIdx = 0;
-  auto InsnMatcherOrError =
-      createAndImportSelDAGMatcher(InsnMatcherTemp, Src, TempOpIdx);
-  if (auto Error = InsnMatcherOrError.takeError())
-    return std::move(Error);
-  InstructionMatcher &InsnMatcher = InsnMatcherOrError.get();
-
   // The root of the match also has constraints on the register bank so that it
   // matches the result instruction.
   unsigned OpIdx = 0;
@@ -2456,16 +2482,37 @@ void GlobalISelEmitter::run(raw_ostream &OS) {
     Rules.push_back(std::move(MatcherOrErr.get()));
   }
 
-  std::stable_sort(Rules.begin(), Rules.end(),
-            [&](const RuleMatcher &A, const RuleMatcher &B) {
-              if (A.isHigherPriorityThan(B)) {
-                assert(!B.isHigherPriorityThan(A) && "Cannot be more important "
-                                                     "and less important at "
-                                                     "the same time");
-                return true;
-              }
-              return false;
-            });
+  const auto &IsRuleEmittingOpcode = [](const RuleMatcher &A, StringRef I) -> bool {
+    const BuildMIAction &BMI = (const BuildMIAction &)*A.Actions[1];
+    if (BMI.I->TheDef->getName() == I)
+      return true;
+    return false;
+  };
+
+  std::stable_sort(Rules.begin(), Rules.end(), [&](const RuleMatcher &A,
+                                                   const RuleMatcher &B) {
+    bool EmitResult = false;
+    bool AIsADD8ri = false;
+    if (IsRuleEmittingOpcode(A, "ADD8ri") && IsRuleEmittingOpcode(B, "INC8r")) {
+      EmitResult = true;
+      AIsADD8ri = true;
+    }
+    if (IsRuleEmittingOpcode(B, "ADD8ri") && IsRuleEmittingOpcode(A, "INC8r"))
+      EmitResult = true;
+
+    if (EmitResult)
+      errs() << "A=" << (AIsADD8ri ? "ADD8ri" : "INC8r") << ", B=" << (!AIsADD8ri ? "ADD8ri" : "INC8r") << "\n";
+    if (A.isHigherPriorityThan(B)) {
+      if (EmitResult)
+        errs() << "A higher priority than B\n";
+      assert(!B.isHigherPriorityThan(A) && "Cannot be more important "
+                                           "and less important at "
+                                           "the same time");
+      return true;
+    } else if (EmitResult)
+      errs() << "A lower priority than B\n";
+    return false;
+  });
 
   std::vector<Record *> ComplexPredicates =
       RK.getAllDerivedDefinitions("GIComplexOperandMatcher");
@@ -2535,16 +2582,9 @@ void GlobalISelEmitter::run(raw_ostream &OS) {
 
   // Emit a table containing the LLT objects needed by the matcher and an enum
   // for the matcher to reference them with.
-  std::vector<LLTCodeGen> TypeObjects = {
-      LLT::scalar(8),      LLT::scalar(16),     LLT::scalar(32),
-      LLT::scalar(64),     LLT::scalar(80),     LLT::vector(8, 1),
-      LLT::vector(16, 1),  LLT::vector(32, 1),  LLT::vector(64, 1),
-      LLT::vector(8, 8),   LLT::vector(16, 8),  LLT::vector(32, 8),
-      LLT::vector(64, 8),  LLT::vector(4, 16),  LLT::vector(8, 16),
-      LLT::vector(16, 16), LLT::vector(32, 16), LLT::vector(2, 32),
-      LLT::vector(4, 32),  LLT::vector(8, 32),  LLT::vector(16, 32),
-      LLT::vector(2, 64),  LLT::vector(4, 64),  LLT::vector(8, 64),
-  };
+  std::vector<LLTCodeGen> TypeObjects;
+  for (const auto &Ty : LLTOperandMatcher::KnownTypes)
+    TypeObjects.push_back(Ty);
   std::sort(TypeObjects.begin(), TypeObjects.end());
   OS << "enum {\n";
   for (const auto &TypeObject : TypeObjects) {