[Mlir-commits] [mlir] 34ed07e - [mlir][sparse] Parser cleanup (#69792)

llvmlistbot at llvm.org llvmlistbot at llvm.org
Mon Oct 23 11:30:07 PDT 2023


Author: Yinying Li
Date: 2023-10-23T14:30:02-04:00
New Revision: 34ed07e6a1a1d5218d1d323577b348568377303d

URL: https://github.com/llvm/llvm-project/commit/34ed07e6a1a1d5218d1d323577b348568377303d
DIFF: https://github.com/llvm/llvm-project/commit/34ed07e6a1a1d5218d1d323577b348568377303d.diff

LOG: [mlir][sparse] Parser cleanup (#69792)

Removed TODOs, FIXMEs and long notes that are more suited for design
doc.

Added: 
    

Modified: 
    mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMap.cpp
    mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMap.h
    mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMapParser.cpp
    mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMapParser.h
    mlir/lib/Dialect/SparseTensor/IR/Detail/LvlTypeParser.cpp
    mlir/lib/Dialect/SparseTensor/IR/Detail/TemplateExtras.h
    mlir/lib/Dialect/SparseTensor/IR/Detail/Var.cpp
    mlir/lib/Dialect/SparseTensor/IR/Detail/Var.h

Removed: 
    


################################################################################
diff  --git a/mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMap.cpp b/mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMap.cpp
index 5f947b67c6d848e..851867926fe679e 100644
--- a/mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMap.cpp
+++ b/mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMap.cpp
@@ -60,16 +60,6 @@ std::optional<int64_t> DimLvlExpr::dyn_castConstantValue() const {
   return k ? std::make_optional(k.getValue()) : std::nullopt;
 }
 
-// This helper method is akin to `AffineExpr::operator==(int64_t)`
-// except it uses a 
diff erent implementation, namely the implementation
-// used within `AsmPrinter::Impl::printAffineExprInternal`.
-//
-// wrengr guesses that `AsmPrinter::Impl::printAffineExprInternal` uses
-// this implementation because it avoids constructing the intermediate
-// `AffineConstantExpr(val)` and thus should in theory be a bit faster.
-// However, if it is indeed faster, then the `AffineExpr::operator==`
-// method should be updated to do this instead.  And if it isn't any
-// faster, then we should be using `AffineExpr::operator==` instead.
 bool DimLvlExpr::hasConstantValue(int64_t val) const {
   const auto k = expr.dyn_cast_or_null<AffineConstantExpr>();
   return k && k.getValue() == val;
@@ -216,12 +206,6 @@ bool DimSpec::isValid(Ranks const &ranks) const {
   return ranks.isValid(var) && (!expr || ranks.isValid(expr));
 }
 
-bool DimSpec::isFunctionOf(VarSet const &vars) const {
-  return vars.occursIn(expr);
-}
-
-void DimSpec::getFreeVars(VarSet &vars) const { vars.add(expr); }
-
 void DimSpec::dump() const {
   print(llvm::errs(), /*wantElision=*/false);
   llvm::errs() << "\n";
@@ -262,12 +246,6 @@ bool LvlSpec::isValid(Ranks const &ranks) const {
   return ranks.isValid(var) && ranks.isValid(expr);
 }
 
-bool LvlSpec::isFunctionOf(VarSet const &vars) const {
-  return vars.occursIn(expr);
-}
-
-void LvlSpec::getFreeVars(VarSet &vars) const { vars.add(expr); }
-
 void LvlSpec::dump() const {
   print(llvm::errs(), /*wantElision=*/false);
   llvm::errs() << "\n";
@@ -301,19 +279,6 @@ DimLvlMap::DimLvlMap(unsigned symRank, ArrayRef<DimSpec> dimSpecs,
   // below cannot cause OOB errors.
   assert(isWF());
 
-  // TODO: Second, we need to infer/validate the `lvlToDim` mapping.
-  // Along the way we should set every `DimSpec::elideExpr` according
-  // to whether the given expression is inferable or not.  Notably, this
-  // needs to happen before the code for setting every `LvlSpec::elideVar`,
-  // since if the LvlVar is only used in elided DimExpr, then the
-  // LvlVar should also be elided.
-  // NOTE: Be sure to use `DimLvlMap::setDimExpr` for setting the new exprs,
-  // to ensure that we maintain the invariant established by `isWF` above.
-
-  // Third, we set every `LvlSpec::elideVar` according to whether that
-  // LvlVar occurs in a non-elided DimExpr (TODO: or CountingExpr).
-  // NOTE: The invariant established by `isWF` ensures that the following
-  // calls to `VarSet::add` cannot raise OOB errors.
   VarSet usedVars(getRanks());
   for (const auto &dimSpec : dimSpecs)
     if (!dimSpec.canElideExpr())

diff  --git a/mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMap.h b/mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMap.h
index 2d02eed2cf9972e..664b49509f070f4 100644
--- a/mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMap.h
+++ b/mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMap.h
@@ -5,11 +5,6 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
-// FIXME(wrengr): The `DimLvlMap` class must be public so that it can
-// be named as the storage representation of the parameter for the tblgen
-// defn of STEA.  We may well need to make the other classes public too,
-// so that the rest of the compiler can use them when necessary.
-//===----------------------------------------------------------------------===//
 
 #ifndef MLIR_DIALECT_SPARSETENSOR_IR_DETAIL_DIMLVLMAP_H
 #define MLIR_DIALECT_SPARSETENSOR_IR_DETAIL_DIMLVLMAP_H
@@ -23,16 +18,8 @@ namespace sparse_tensor {
 namespace ir_detail {
 
 //===----------------------------------------------------------------------===//
-// TODO(wrengr): Give this enum a better name, so that it fits together
-// with the name of the `DimLvlExpr` class (which may also want a better
-// name).  Perhaps make this a nested-type too.
-//
-// NOTE: In the future we will extend this enum to include "counting
-// expressions" required for supporting ITPACK/ELL.  Therefore the current
-// underlying-type and representation values should not be relied upon.
 enum class ExprKind : bool { Dimension = false, Level = true };
 
-// TODO(wrengr): still needs a better name....
 constexpr VarKind getVarKindAllowedInExpr(ExprKind ek) {
   using VK = std::underlying_type_t<VarKind>;
   return VarKind{2 * static_cast<VK>(!to_underlying(ek))};
@@ -41,19 +28,8 @@ static_assert(getVarKindAllowedInExpr(ExprKind::Dimension) == VarKind::Level &&
               getVarKindAllowedInExpr(ExprKind::Level) == VarKind::Dimension);
 
 //===----------------------------------------------------------------------===//
-// TODO(wrengr): The goal of this class is to capture a proof that
-// we've verified that the given `AffineExpr` only has variables of the
-// appropriate kind(s).  So we need to actually prove/verify that in the
-// ctor or all its callsites!
 class DimLvlExpr {
 private:
-  // FIXME(wrengr): Per <https://llvm.org/docs/HowToSetUpLLVMStyleRTTI.html>,
-  // the `kind` field should be private and const.  However, beware
-  // that if we mark any field as `const` or if the fields have 
diff ering
-  // `private`/`protected` privileges then the `IsZeroCostAbstraction`
-  // assertion will fail!
-  // (Also, iirc, if we end up moving the `expr` to the subclasses
-  // instead, that'll also cause `IsZeroCostAbstraction` to fail.)
   ExprKind kind;
   AffineExpr expr;
 
@@ -100,11 +76,6 @@ class DimLvlExpr {
   //
   // Getters for handling `AffineExpr` subclasses.
   //
-  // TODO(wrengr): is there any way to make these typesafe without too much
-  // templating?
-  // TODO(wrengr): Most if not all of these don't actually need to be
-  // methods, they could be free-functions instead.
-  //
   Var castAnyVar() const;
   std::optional<Var> dyn_castAnyVar() const;
   SymVar castSymVar() const;
@@ -131,9 +102,6 @@ class DimLvlExpr {
   // Variant of `mlir::AsmPrinter::Impl::BindingStrength`
   enum class BindingStrength : bool { Weak = false, Strong = true };
 
-  // TODO(wrengr): Does our version of `printAffineExprInternal` really
-  // need to be a method, or could it be a free-function instead? (assuming
-  // `BindingStrength` goes with it).
   void printAffineExprInternal(llvm::raw_ostream &os,
                                BindingStrength enclosingTightness) const;
   void printStrong(llvm::raw_ostream &os) const {
@@ -145,12 +113,7 @@ class DimLvlExpr {
 };
 static_assert(IsZeroCostAbstraction<DimLvlExpr>);
 
-// FUTURE_CL(wrengr): It would be nice to have the subclasses override
-// `getRHS`, `getLHS`, `unpackBinop`, and `castDimLvlVar` to give them
-// the proper covariant return types.
-//
 class DimExpr final : public DimLvlExpr {
-  // FIXME(wrengr): These two are needed for the current RTTI implementation.
   friend class DimLvlExpr;
   constexpr explicit DimExpr(DimLvlExpr expr) : DimLvlExpr(expr) {}
 
@@ -170,7 +133,6 @@ class DimExpr final : public DimLvlExpr {
 static_assert(IsZeroCostAbstraction<DimExpr>);
 
 class LvlExpr final : public DimLvlExpr {
-  // FIXME(wrengr): These two are needed for the current RTTI implementation.
   friend class DimLvlExpr;
   constexpr explicit LvlExpr(DimLvlExpr expr) : DimLvlExpr(expr) {}
 
@@ -189,7 +151,6 @@ class LvlExpr final : public DimLvlExpr {
 };
 static_assert(IsZeroCostAbstraction<LvlExpr>);
 
-// FIXME(wrengr): See comments elsewhere re RTTI implementation issues/questions
 template <typename U>
 constexpr bool DimLvlExpr::isa() const {
   if constexpr (std::is_same_v<U, DimExpr>)
@@ -247,18 +208,12 @@ class DimSpec final {
   /// the result of this predicate.
   [[nodiscard]] bool isValid(Ranks const &ranks) const;
 
-  // TODO(wrengr): Use it or loose it.
-  bool isFunctionOf(Var var) const;
-  bool isFunctionOf(VarSet const &vars) const;
-  void getFreeVars(VarSet &vars) const;
-
   std::string str(bool wantElision = true) const;
   void print(llvm::raw_ostream &os, bool wantElision = true) const;
   void print(AsmPrinter &printer, bool wantElision = true) const;
   void dump() const;
 };
-// Although this class is more than just a newtype/wrapper, we do want
-// to ensure that storing them into `SmallVector` is efficient.
+
 static_assert(IsZeroCostAbstraction<DimSpec>);
 
 //===----------------------------------------------------------------------===//
@@ -270,13 +225,6 @@ class LvlSpec final {
   /// whereas the `DimLvlMap` ctor will reset this as appropriate.
   bool elideVar = false;
   /// The level-expression.
-  //
-  // NOTE: For now we use `LvlExpr` because all level-expressions must be
-  // `AffineExpr`; however, in the future we will also want to allow "counting
-  // expressions", and potentially other kinds of non-affine level-expressions.
-  // Which kinds of `DimLvlExpr` are allowed will depend on the `DimLevelType`,
-  // so we may consider defining another class for pairing those two together
-  // to ensure that the pair is well-formed.
   LvlExpr expr;
   /// The level-type (== level-format + lvl-properties).
   DimLevelType type;
@@ -298,23 +246,14 @@ class LvlSpec final {
 
   /// Checks whether the variables bound/used by this spec are valid
   /// with respect to the given ranks.
-  //
-  // NOTE: Once we introduce "counting expressions" this will need
-  // a more sophisticated implementation than `DimSpec::isValid` does.
   [[nodiscard]] bool isValid(Ranks const &ranks) const;
 
-  // TODO(wrengr): Use it or loose it.
-  bool isFunctionOf(Var var) const;
-  bool isFunctionOf(VarSet const &vars) const;
-  void getFreeVars(VarSet &vars) const;
-
   std::string str(bool wantElision = true) const;
   void print(llvm::raw_ostream &os, bool wantElision = true) const;
   void print(AsmPrinter &printer, bool wantElision = true) const;
   void dump() const;
 };
-// Although this class is more than just a newtype/wrapper, we do want
-// to ensure that storing them into `SmallVector` is efficient.
+
 static_assert(IsZeroCostAbstraction<LvlSpec>);
 
 //===----------------------------------------------------------------------===//

diff  --git a/mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMapParser.cpp b/mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMapParser.cpp
index 680411f8008ea3d..6fb69d1397e6cfb 100644
--- a/mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMapParser.cpp
+++ b/mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMapParser.cpp
@@ -44,42 +44,20 @@ OptionalParseResult DimLvlMapParser::parseVar(VarKind vk, bool isOptional,
                                               VarInfo::ID &varID,
                                               bool &didCreate) {
   // Save the current location so that we can have error messages point to
-  // the right place.  Note that `Parser::emitWrongTokenError` starts off
-  // with the same location as `AsmParserImpl::getCurrentLocation` returns;
-  // however, `Parser` will then do some various munging with the location
-  // before actually using it, so `AsmParser::emitError` can't quite be used
-  // as a drop-in replacement for `Parser::emitWrongTokenError`.
+  // the right place.
   const auto loc = parser.getCurrentLocation();
-
-  // Several things to note.
-  // (1) the `Parser::isCurrentTokenAKeyword` method checks the exact
-  //     same conditions as the `AffineParser.cpp`-static free-function
-  //     `isIdentifier` which is used by `AffineParser::parseBareIdExpr`.
-  // (2) the `{Parser,AsmParserImpl}::parseOptionalKeyword(StringRef*)`
-  //     methods do the same song and dance about using
-  //     `isCurrentTokenAKeyword`, `getTokenSpelling`, et `consumeToken` as we
-  //     would want to do if we could use the `Parser` class directly.  It
-  //     doesn't provide the nice error handling we want, but we can work around
-  //     that.
   StringRef name;
   if (failed(parser.parseOptionalKeyword(&name))) {
-    // If not actually optional, then `emitError`.
     ERROR_IF(!isOptional, "expected bare identifier")
-    // If is actually optional, then return the null `OptionalParseResult`.
     return std::nullopt;
   }
 
-  // I don't know if we need to worry about the possibility of the caller
-  // recovering from error and then reusing the `DimLvlMapParser` for subsequent
-  // `parseVar`, but I'm erring on the side of caution by distinguishing
-  // all three possible creation policies.
   if (const auto res = env.lookupOrCreate(creationPolicy, name, loc, vk)) {
     varID = res->first;
     didCreate = res->second;
     return success();
   }
-  // TODO(wrengr): these error messages make sense for our intended usage,
-  // but not in general; but it's unclear how best to factor that part out.
+
   switch (creationPolicy) {
   case Policy::MustNot:
     return parser.emitError(loc, "use of undeclared identifier '" + name + "'");
@@ -167,8 +145,6 @@ FailureOr<DimLvlMap> DimLvlMapParser::parseDimLvlMap() {
   FAILURE_IF_FAILED(parseDimSpecList())
   FAILURE_IF_FAILED(parser.parseArrow())
   FAILURE_IF_FAILED(parseLvlSpecList())
-  // TODO(wrengr): Try to improve the error messages from
-  // `VarEnv::emitErrorIfAnyUnbound`.
   InFlightDiagnostic ifd = env.emitErrorIfAnyUnbound(parser);
   if (failed(ifd))
     return ifd;
@@ -182,29 +158,6 @@ ParseResult DimLvlMapParser::parseSymbolBindingList() {
       " in symbol binding list");
 }
 
-// FIXME: The forward-declaration of level-vars is a stop-gap workaround
-// so that we can reuse `AsmParser::parseAffineExpr` in the definition of
-// `DimLvlMapParser::parseDimSpec`.  (In particular, note that all the
-// variables must be bound before entering `AsmParser::parseAffineExpr`,
-// since that method requires every variable to already have a fixed/known
-// `Var::Num`.)
-//
-// However, the forward-declaration list duplicates information which is
-// already encoded by the level-var bindings in `parseLvlSpecList` (namely:
-// the names of the variables themselves, and the order in which the names
-// are bound).  This redundancy causes bad UX, and also means we must be
-// sure to verify consistency between the two sources of information.
-//
-// Therefore, it would be best to remove the forward-declaration list from
-// the syntax.  This can be achieved by implementing our own version of
-// `AffineParser::parseAffineExpr` which calls
-// `parseVarUsage(_,requireKnown=false)` for variables and stores the resulting
-// `VarInfo::ID` in the expression tree (instead of demanding it be resolved to
-// some `Var::Num` immediately).  This would also enable us to use the `VarEnv`
-// directly, rather than building the `{dims,lvls}AndSymbols` lists on the
-// side, and thus would also enable us to avoid the O(n^2) behavior of copying
-// `DimLvlParser::{dims,lvls}AndSymbols` into `AffineParser::dimsAndSymbols`
-// every time `AsmParser::parseAffineExpr` is called.
 ParseResult DimLvlMapParser::parseLvlVarBindingList() {
   return parser.parseCommaSeparatedList(
       OpAsmParser::Delimiter::OptionalBraces,
@@ -233,9 +186,6 @@ ParseResult DimLvlMapParser::parseDimSpec() {
   AffineExpr affine;
   if (succeeded(parser.parseOptionalEqual())) {
     // Parse the dim affine expr, with only any lvl-vars in scope.
-    // FIXME(wrengr): This still has the O(n^2) behavior of copying
-    // our `lvlsAndSymbols` into the `AffineParser::dimsAndSymbols`
-    // field every time `parseDimSpec` is called.
     FAILURE_IF_FAILED(parser.parseAffineExpr(lvlsAndSymbols, affine))
   }
   DimExpr expr{affine};
@@ -304,9 +254,6 @@ static inline Twine nth(Var::Num n) {
   }
 }
 
-// NOTE: This is factored out as a separate method only because `Var`
-// lacks a default-ctor, which makes this conditional 
diff icult to inline
-// at the one call-site.
 FailureOr<LvlVar>
 DimLvlMapParser::parseLvlVarBinding(bool requireLvlVarBinding) {
   // Nothing to parse, just bind an unnamed variable.
@@ -336,17 +283,14 @@ DimLvlMapParser::parseLvlVarBinding(bool requireLvlVarBinding) {
 }
 
 ParseResult DimLvlMapParser::parseLvlSpec(bool requireLvlVarBinding) {
-  // Parse the optional lvl-var binding.  (Actually, `requireLvlVarBinding`
-  // specifies whether that "optional" is actually Must or MustNot.)
+  // Parse the optional lvl-var binding. `requireLvlVarBinding`
+  // specifies whether that "optional" is actually Must or MustNot.
   const auto varRes = parseLvlVarBinding(requireLvlVarBinding);
   FAILURE_IF_FAILED(varRes)
   const LvlVar var = *varRes;
 
   // Parse the lvl affine expr, with only the dim-vars in scope.
   AffineExpr affine;
-  // FIXME(wrengr): This still has the O(n^2) behavior of copying
-  // our `dimsAndSymbols` into the `AffineParser::dimsAndSymbols`
-  // field every time `parseLvlSpec` is called.
   FAILURE_IF_FAILED(parser.parseAffineExpr(dimsAndSymbols, affine))
   LvlExpr expr{affine};
 

diff  --git a/mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMapParser.h b/mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMapParser.h
index 013a89ea172b0b5..11f727c40644ae1 100644
--- a/mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMapParser.h
+++ b/mlir/lib/Dialect/SparseTensor/IR/Detail/DimLvlMapParser.h
@@ -42,39 +42,32 @@ class DimLvlMapParser final {
   FailureOr<DimLvlMap> parseDimLvlMap();
 
 private:
-  /// The core code for parsing `Var`.  This method abstracts out a lot
-  /// of complex details to avoid code duplication; however, client code
-  /// should prefer using `parseVarUsage` and `parseVarBinding` rather than
-  /// calling this method directly.
+  /// Client code should prefer using `parseVarUsage`
+  /// and `parseVarBinding` rather than calling this method directly.
   OptionalParseResult parseVar(VarKind vk, bool isOptional,
                                Policy creationPolicy, VarInfo::ID &id,
                                bool &didCreate);
 
-  /// Parse a variable occurence which is a *use* of that variable.
-  /// The `requireKnown` parameter specifies how to handle the case of
-  /// encountering a valid variable name which is currently unused: when
-  /// `requireKnown=true`, an error is raised; when `requireKnown=false`,
+  /// Parses a variable occurence which is a *use* of that variable.
+  /// When a valid variable name is currently unused, if
+  /// `requireKnown=true`, an error is raised; if `requireKnown=false`,
   /// a new unbound variable will be created.
-  ///
-  /// NOTE: Just because a variable is *known* (i.e., the name has been
-  /// associated with an `VarInfo::ID`), does not mean that the variable
-  /// is actually *in scope*.
   FailureOr<VarInfo::ID> parseVarUsage(VarKind vk, bool requireKnown);
 
-  /// Parse a variable occurence which is a *binding* of that variable.
+  /// Parses a variable occurence which is a *binding* of that variable.
   /// The `requireKnown` parameter is for handling the binding of
   /// forward-declared variables.
   FailureOr<VarInfo::ID> parseVarBinding(VarKind vk, bool requireKnown = false);
 
-  /// Parse an optional variable binding.  When the next token is
+  /// Parses an optional variable binding. When the next token is
   /// not a valid variable name, this will bind a new unnamed variable.
   /// The returned `bool` indicates whether a variable name was parsed.
   FailureOr<std::pair<Var, bool>>
   parseOptionalVarBinding(VarKind vk, bool requireKnown = false);
 
   /// Binds the given variable: both updating the `VarEnv` itself, and
-  /// also updating the `{dims,lvls}AndSymbols` lists (which will be passed
-  /// to `AsmParser::parseAffineExpr`).  This method is already called by the
+  /// the `{dims,lvls}AndSymbols` lists (which will be passed
+  /// to `AsmParser::parseAffineExpr`). This method is already called by the
   /// `parseVarBinding`/`parseOptionalVarBinding` methods, therefore should
   /// not need to be called elsewhere.
   Var bindVar(llvm::SMLoc loc, VarInfo::ID id);

diff  --git a/mlir/lib/Dialect/SparseTensor/IR/Detail/LvlTypeParser.cpp b/mlir/lib/Dialect/SparseTensor/IR/Detail/LvlTypeParser.cpp
index 053e067fff64ddb..8cc7068e3113aff 100644
--- a/mlir/lib/Dialect/SparseTensor/IR/Detail/LvlTypeParser.cpp
+++ b/mlir/lib/Dialect/SparseTensor/IR/Detail/LvlTypeParser.cpp
@@ -14,29 +14,11 @@ using namespace mlir::sparse_tensor;
 using namespace mlir::sparse_tensor::ir_detail;
 
 //===----------------------------------------------------------------------===//
-// TODO(wrengr): rephrase these to do the trick for gobbling up any trailing
-// semicolon
-//
-// NOTE: There's no way for `FAILURE_IF_FAILED` to simultaneously support
-// both `OptionalParseResult` and `InFlightDiagnostic` return types.
-// We can get the compiler to accept the code if we returned "`{}`",
-// however for `OptionalParseResult` that would become the nullopt result,
-// whereas for `InFlightDiagnostic` it would become a result that can
-// be implicitly converted to success.  By using "`failure()`" we ensure
-// that `OptionalParseResult` behaves as intended, however that means the
-// macro cannot be used for `InFlightDiagnostic` since there's no implicit
-// conversion.
 #define FAILURE_IF_FAILED(STMT)                                                \
   if (failed(STMT)) {                                                          \
     return failure();                                                          \
   }
 
-// Although `ERROR_IF` is phrased to return `InFlightDiagnostic`, that type
-// can be implicitly converted to all four of `LogicalResult, `FailureOr`,
-// `ParseResult`, and `OptionalParseResult`.  (However, beware that the
-// conversion to `OptionalParseResult` doesn't properly delegate to
-// `InFlightDiagnostic::operator ParseResult`.)
-//
 // NOTE: this macro assumes `AsmParser parser` and `SMLoc loc` are in scope.
 #define ERROR_IF(COND, MSG)                                                    \
   if (COND) {                                                                  \

diff  --git a/mlir/lib/Dialect/SparseTensor/IR/Detail/TemplateExtras.h b/mlir/lib/Dialect/SparseTensor/IR/Detail/TemplateExtras.h
index 5c222dd966f4f73..7f0c1fd8c46c78b 100644
--- a/mlir/lib/Dialect/SparseTensor/IR/Detail/TemplateExtras.h
+++ b/mlir/lib/Dialect/SparseTensor/IR/Detail/TemplateExtras.h
@@ -19,8 +19,6 @@ namespace sparse_tensor {
 namespace ir_detail {
 
 //===----------------------------------------------------------------------===//
-// These two templates are like `AsmPrinter::{,detect_}has_print_method`,
-// except they detect print methods taking `raw_ostream` (not `AsmPrinter`).
 template <typename T>
 using has_print_method =
     decltype(std::declval<T>().print(std::declval<llvm::raw_ostream &>()));
@@ -31,9 +29,7 @@ using enable_if_has_print_method =
     std::enable_if_t<detect_has_print_method<T>::value, R>;
 
 /// Generic template for defining `operator<<` overloads which delegate
-/// to `T::print(raw_ostream&) const`.  Note that there's already another
-/// generic template which defines `operator<<(AsmPrinterT&, T const&)`
-/// via delegating to `operator<<(raw_ostream&, T const&)`.
+/// to `T::print(raw_ostream&) const`.
 template <typename T>
 inline enable_if_has_print_method<T, llvm::raw_ostream &>
 operator<<(llvm::raw_ostream &os, T const &t) {
@@ -42,9 +38,7 @@ operator<<(llvm::raw_ostream &os, T const &t) {
 }
 
 //===----------------------------------------------------------------------===//
-/// Convert an enum to its underlying type.  This template is designed
-/// to avoid introducing implicit conversions to other integral types,
-/// and is a backport of C++23 `std::to_underlying`.
+/// Convert an enum to its underlying type.
 template <typename Enum>
 constexpr std::underlying_type_t<Enum> to_underlying(Enum e) noexcept {
   return static_cast<std::underlying_type_t<Enum>>(e);
@@ -53,28 +47,12 @@ constexpr std::underlying_type_t<Enum> to_underlying(Enum e) noexcept {
 //===----------------------------------------------------------------------===//
 template <typename T>
 static constexpr bool IsZeroCostAbstraction =
-    // These two predicates license the compiler to make several optimizations;
-    // some of which are explicitly documented by the C++ standard:
-    // <https://en.cppreference.com/w/cpp/types/is_trivially_copyable#Notes>
-    // <https://en.cppreference.com/w/cpp/types/is_trivially_destructible#Notes>
-    // However, some key optimizations aren't mentioned by the standard; e.g.,
-    // that trivially-copyable enables passing-by-value, and the conjunction
-    // of trivially-copyable and trivially-destructible enables passing those
-    // values in registers rather than on the stack (cf.,
-    // <https://www.agner.org/optimize/calling_conventions.pdf>).
+    // These two predicates license the compiler to make optimizations.
     std::is_trivially_copyable_v<T> && std::is_trivially_destructible_v<T> &&
-    // This one helps ensure ABI compatibility (e.g., padding and alignment):
-    // <https://en.cppreference.com/w/cpp/types/is_standard_layout#Notes>
-    // <https://en.cppreference.com/w/cpp/language/classes#Standard-layout_class>
-    // In particular, the standard mentions that passing/returning a `struct`
-    // by value can sometimes introduce ABI overhead compared to using
-    // `enum class`; so this assertion is attempting to avoid that.
-    // <https://en.cppreference.com/w/cpp/language/enum#enum_relaxed_init_cpp17>
+    // This helps ensure ABI compatibility (e.g., padding and alignment).
     std::is_standard_layout_v<T> &&
     // These two are what SmallVector uses to determine whether it can
-    // use memcpy.  The commentary there mentions that it's intended to be
-    // an approximation of `is_trivially_copyable`, so this may be redundant
-    // with the above, but we include it just to make sure.
+    // use memcpy.
     std::is_trivially_copy_constructible<T>::value &&
     std::is_trivially_move_constructible<T>::value;
 

diff  --git a/mlir/lib/Dialect/SparseTensor/IR/Detail/Var.cpp b/mlir/lib/Dialect/SparseTensor/IR/Detail/Var.cpp
index 44eba668021ba79..966e32401c1f9e3 100644
--- a/mlir/lib/Dialect/SparseTensor/IR/Detail/Var.cpp
+++ b/mlir/lib/Dialect/SparseTensor/IR/Detail/Var.cpp
@@ -61,9 +61,6 @@ bool Ranks::isValid(DimLvlExpr expr) const {
   int64_t maxSym = -1, maxVar = -1;
   mlir::getMaxDimAndSymbol<ArrayRef<AffineExpr>>({{expr.getAffineExpr()}},
                                                  maxVar, maxSym);
-  // TODO(wrengr): We may want to add a call to `LLVM_DEBUG` like
-  // `willBeValidAffineMap` does.  And/or should return `InFlightDiagnostic`
-  // instead of bool.
   return maxSym < getSymRank() && maxVar < getRank(expr.getAllowedVarKind());
 }
 
@@ -72,10 +69,6 @@ bool Ranks::isValid(DimLvlExpr expr) const {
 //===----------------------------------------------------------------------===//
 
 VarSet::VarSet(Ranks const &ranks) {
-  // NOTE: We must not use `reserve` here, since that doesn't change
-  // the `size` of the bitvectors and therefore will result in unexpected
-  // OOB errors.  Either `resize` or copy/move-ctor work; we opt for the
-  // move-ctor since it should be (marginally) more efficient.
   for (const auto vk : everyVarKind)
     impl[vk] = llvm::SmallBitVector(ranks.getRank(vk));
   assert(getRanks() == ranks);
@@ -180,9 +173,6 @@ void VarInfo::setNum(Var::Num n) {
 
 /// Helper function for `assertUsageConsistency` to better handle SMLoc
 /// mismatches.
-// TODO(wrengr): If we switch to the `LocatedVar` design, then there's
-// no need for anything like `minSMLoc` since `assertUsageConsistency`
-// won't need to do anything about locations.
 LLVM_ATTRIBUTE_UNUSED static llvm::SMLoc
 minSMLoc(AsmParser &parser, llvm::SMLoc sm1, llvm::SMLoc sm2) {
   const auto loc1 = parser.getEncodedSourceLoc(sm1).dyn_cast<FileLineColLoc>();
@@ -201,28 +191,13 @@ bool isInternalConsistent(VarEnv const &env, VarInfo::ID id, StringRef name) {
   return (var.getName() == name && var.getID() == id);
 }
 
-// NOTE(wrengr): if we can actually obtain an `AsmParser` for `minSMLoc`
-// (or find some other way to convert SMLoc to FileLineColLoc), then this
-// would no longer be `const VarEnv` (and couldn't be a free-function either).
 bool isUsageConsistent(VarEnv const &env, VarInfo::ID id, llvm::SMLoc loc,
                        VarKind vk) {
   const auto &var = env.access(id);
-  // Since the same variable can occur at several locations,
-  // it would not be appropriate to do `assert(var.getLoc() == loc)`.
-  /* TODO(wrengr):
-  const auto minLoc = minSMLoc(_, var.getLoc(), loc);
-  assert(minLoc && "Location mismatch/incompatibility");
-  var.loc = minLoc;
-  // */
   return var.getKind() == vk;
 }
 
 std::optional<VarInfo::ID> VarEnv::lookup(StringRef name) const {
-  // NOTE: `StringMap::lookup` will return a default-constructed value if
-  // the key isn't found; which for enums means zero, and therefore makes
-  // it impossible to distinguish between actual zero-VarInfo::ID vs not-found.
-  // Whereas `StringMap::at` asserts that the key is found, which we don't
-  // want either.
   const auto iter = ids.find(name);
   if (iter == ids.end())
     return std::nullopt;
@@ -277,22 +252,10 @@ Var VarEnv::bindUnusedVar(VarKind vk) { return Var(vk, nextNum[vk]++); }
 Var VarEnv::bindVar(VarInfo::ID id) {
   auto &info = access(id);
   const auto var = bindUnusedVar(info.getKind());
-  // NOTE: `setNum` already checks wellformedness of the `Var::Num`.
   info.setNum(var.getNum());
   return var;
 }
 
-// TODO(wrengr): Alternatively there's `mlir::emitError(Location, Twine const&)`
-// which is what `Operation::emitError` uses; though I'm not sure if
-// that's appropriate to use here...  But if it is, then that means
-// we can have `VarInfo` store `Location` rather than `SMLoc`, which
-// means we can use `FusedLoc` to handle the combination issue in
-// `VarEnv::lookupOrCreate`.
-//
-// TODO(wrengr): is there any way to combine multiple IFDs, so that
-// we can report all unbound variables instead of just the first one
-// encountered?
-//
 InFlightDiagnostic VarEnv::emitErrorIfAnyUnbound(AsmParser &parser) const {
   for (const auto &var : vars)
     if (!var.hasNum())

diff  --git a/mlir/lib/Dialect/SparseTensor/IR/Detail/Var.h b/mlir/lib/Dialect/SparseTensor/IR/Detail/Var.h
index 145586a83a2528c..2606dd399eec81c 100644
--- a/mlir/lib/Dialect/SparseTensor/IR/Detail/Var.h
+++ b/mlir/lib/Dialect/SparseTensor/IR/Detail/Var.h
@@ -20,36 +20,6 @@ namespace mlir {
 namespace sparse_tensor {
 namespace ir_detail {
 
-// Throughout this namespace we use the name `isWF` (is "well-formed")
-// for predicates that detect intrinsic structural integrity criteria,
-// and hence which should always be assertively true.  Whereas we reserve
-// the name `isValid` for predicates that detect extrinsic semantic
-// integrity criteria, and hence which may legitimately return false even
-// in well-formed programs.  Moreover, "validity" is often a relational
-// or contextual property, and therefore the same term may be considered
-// valid in one context yet invalid in another.
-//
-// As an example of why we make this distinction, consider `Var`.
-// A variable is well-formed if its kind and identifier are both well-formed;
-// this can be checked locally, and the resulting truth-value holds globally.
-// Whereas, a variable is valid with respect to a particular `Ranks` only if
-// it is within bounds; and a variable is valid with respect to a particular
-// `DimLvlMap` only if the variable is bound and all uses of the variable
-// are within the scope of that binding.
-
-// Throughout this namespace we use `enum class` types to form "newtypes".
-// The enum-based implementation of newtypes only serves to block implicit
-// conversions; it cannot enforce any wellformedness constraints, since
-// `enum class` permits using direct-list-initialization to construct
-// arbitrary values[1].  Consequently, we use the syntax "`E{u}`" whenever
-// we intend that ctor to be a noop (i.e., `std::is_same_v<decltype(u),
-// std::underlying_type_t<E>>`), since the compiler will ensure that that's
-// the case.  Whereas we only use the "`static_cast<E>(u)`" syntax when we
-// specifically intend to introduce conversions.
-//
-// [1]:
-// <https://en.cppreference.com/w/cpp/language/enum#enum_relaxed_init_cpp17>
-
 //===----------------------------------------------------------------------===//
 /// The three kinds of variables that `Var` can be.
 ///
@@ -93,37 +63,9 @@ using VarKindArray = llvm::EnumeratedArray<T, VarKind, VarKind::Level>;
 
 //===----------------------------------------------------------------------===//
 /// A concrete variable, to be used in our variant of `AffineExpr`.
+/// Client-facing class for `VarKind` + `Var::Num` pairs, with RTTI
+/// support for subclasses with a fixed `VarKind`.
 class Var {
-  // Design Note: This class makes several distinctions which may at first
-  // seem unnecessary but are in fact needed for implementation reasons.
-  // These distinctions are summarized as follows:
-  //
-  // * `Var`
-  //   Client-facing class for `VarKind` + `Var::Num` pairs, with RTTI
-  //   support for subclasses with a fixed `VarKind`.
-  // * `Var::Num`
-  //   Client-facing typedef for the type of variable numbers; defined
-  //   so that client code can use it to disambiguate/document when things
-  //   are intended to be variable numbers, as opposed to some other thing
-  //   which happens to be represented as `unsigned`.
-  // * `Var::Storage`
-  //   Private typedef for the storage of `Var::Impl`; defined only because
-  //   it's also needed for defining `kMaxNum`.  Note that this type must be
-  //   kept distinct from `Var::Num`: not only can they be 
diff erent C++ types
-  //   (even though they currently happen to be the same), but also because
-  //   they use 
diff erent bitwise representations.
-  // * `Var::Impl`
-  //   The underlying implementation of `Var`; needed by RTTI to serve as
-  //   an intermediary between `Var` and `Var::Storage`.  That is, we want
-  //   the RTTI methods to select the `U(Var::Impl)` ctor, without any
-  //   possibility of confusing that with the `U(Var::Num)` ctor nor with
-  //   the copy-ctor.  (Although the `U(Var::Impl)` ctor is effectively
-  //   identical to the copy-ctor, it doesn't have the type that C++ expects
-  //   for a copy-ctor.)
-  //
-  // TODO: See if it'd be cleaner to use "llvm/ADT/Bitfields.h" in lieu
-  // of doing our own bitbashing (though that seems to only be used by LLVM
-  // for defining machine/assembly ops, and not anywhere else in LLVM/MLIR).
 public:
   /// Typedef for the type of variable numbers.
   using Num = unsigned;
@@ -179,7 +121,6 @@ class Var {
 public:
   constexpr Var(VarKind vk, Num n) : impl(Impl(vk, n)) {}
   Var(AffineSymbolExpr sym) : Var(VarKind::Symbol, sym.getPosition()) {}
-  // TODO(wrengr): Should make the first argument an `ExprKind` instead...?
   Var(VarKind vk, AffineDimExpr var) : Var(vk, var.getPosition()) {
     assert(vk != VarKind::Symbol);
   }
@@ -248,11 +189,6 @@ constexpr bool Var::isa() const {
     return getKind() == VarKind::Dimension;
   if constexpr (std::is_same_v<U, LvlVar>)
     return getKind() == VarKind::Level;
-  // NOTE: The `AffineExpr::isa` implementation doesn't have a fallthrough
-  // case returning `false`; wrengr guesses that's so things will fail
-  // to compile whenever `!std::is_base_of<Var, U>`.  Though it's unclear
-  // why they implemented it that way rather than using SFINAE for that,
-  // especially since it would give better error messages.
 }
 
 template <typename U>
@@ -310,19 +246,7 @@ static_assert(IsZeroCostAbstraction<Ranks>);
 
 //===----------------------------------------------------------------------===//
 /// Efficient representation of a set of `Var`.
-///
-/// NOTE: For the `contains`/`occursIn` methods: if variables occurring in
-/// the method parameter are OOB for the `VarSet`, then these methods will
-/// always return false.  However, for the `add` methods: OOB parameters
-/// cause undefined behavior.  Currently the `add` methods will raise an
-/// assertion error; though we may change that behavior in the future
-/// (e.g., to resize the underlying bitvectors).
 class VarSet final {
-  // If we're willing to give up the possibility of resizing the
-  // individual bitvectors, then we could flatten this into a single
-  // bitvector (akin to how `mlir::presburger::PresburgerSpace` does it);
-  // however, doing so would greatly complicate the implementation of the
-  // `occursIn(VarSet)` method.
   VarKindArray<llvm::SmallBitVector> impl;
 
 public:
@@ -335,11 +259,15 @@ class VarSet final {
   Ranks getRanks() const {
     return Ranks(getSymRank(), getDimRank(), getLvlRank());
   }
-
+  /// For the `contains`/`occursIn` methods: if variables occurring in
+  /// the method parameter are OOB for the `VarSet`, then these methods will
+  /// always return false.
   bool contains(Var var) const;
   bool occursIn(VarSet const &vars) const;
   bool occursIn(DimLvlExpr expr) const;
 
+  /// For the `add` methods: OOB parameters cause undefined behavior.
+  /// Currently the `add` methods will raise an assertion error.
   void add(Var var);
   void add(VarSet const &vars);
   void add(DimLvlExpr expr);
@@ -394,10 +322,6 @@ class VarInfo final {
     return num ? std::make_optional(Var(kind, *num)) : std::nullopt;
   }
 };
-// We don't actually require this, since `VarInfo` is a proper struct
-// rather than a newtype.  But it passes, so for now we'll keep it around.
-// TODO: Uncomment the static assert, it fails the build with gcc7 right now.
-// static_assert(IsZeroCostAbstraction<VarInfo>);
 
 //===----------------------------------------------------------------------===//
 enum class Policy { MustNot, May, Must };
@@ -423,9 +347,6 @@ class VarEnv final {
   /// object is mutated during the lifetime of the pointer.  Therefore,
   /// client code should not store the reference nor otherwise allow it
   /// to live too long.
-  //
-  // FUTURE_CL(wrengr): Consider trying to define/use a nested class
-  // `struct{VarEnv*; VarInfo::ID}` akin to `BitVector::reference`.
   VarInfo const &access(VarInfo::ID id) const {
     // `SmallVector::operator[]` already asserts the index is in-bounds.
     return vars[to_underlying(id)];
@@ -443,29 +364,24 @@ class VarEnv final {
   }
 
 public:
-  /// Attempts to look up the variable with the given name.
+  /// Looks up the variable with the given name.
   std::optional<VarInfo::ID> lookup(StringRef name) const;
 
-  /// Attempts to create a new currently-unbound variable.  When a variable
+  /// Creates a new currently-unbound variable.  When a variable
   /// of that name already exists: if `verifyUsage` is true, then will assert
   /// that the variable has the same kind and a consistent location; otherwise,
   /// when `verifyUsage` is false, this is a noop.  Returns the identifier
-  /// for the variable with the given name (i.e., either the newly created
-  /// variable, or the pre-existing variable), and a bool indicating whether
+  /// for the variable with the given name, and a bool indicating whether
   /// a new variable was created.
   std::optional<std::pair<VarInfo::ID, bool>>
   create(StringRef name, llvm::SMLoc loc, VarKind vk, bool verifyUsage = false);
 
-  /// Attempts to lookup or create a variable according to the given
+  /// Looks up or creates a variable according to the given
   /// `Policy`.  Returns nullopt in one of two circumstances:
   /// (1) the policy says we `Must` create, yet the variable already exists;
   /// (2) the policy says we `MustNot` create, yet no such variable exists.
   /// Otherwise, if the variable already exists then it is validated against
   /// the given kind and location to ensure consistency.
-  //
-  // TODO(wrengr): Define an enum of error codes, to avoid `nullopt`-blindness
-  // TODO(wrengr): Prolly want to rename this to `create` and move the
-  // current method of that name to being a private `createImpl`.
   std::optional<std::pair<VarInfo::ID, bool>>
   lookupOrCreate(Policy creationPolicy, StringRef name, llvm::SMLoc loc,
                  VarKind vk);


        


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