[Mlir-commits] [mlir] 4803453 - [MLIR] Introduce op trait PolyhedralScope (revised)

Uday Bondhugula llvmlistbot at llvm.org
Wed Apr 29 03:40:06 PDT 2020


Author: Uday Bondhugula
Date: 2020-04-29T16:08:23+05:30
New Revision: 480345381a3ec9b067bbccc509e2462c10cfc9e3

URL: https://github.com/llvm/llvm-project/commit/480345381a3ec9b067bbccc509e2462c10cfc9e3
DIFF: https://github.com/llvm/llvm-project/commit/480345381a3ec9b067bbccc509e2462c10cfc9e3.diff

LOG: [MLIR] Introduce op trait PolyhedralScope (revised)

(A previous version of this, dd2c639c3cd397dfef941186fb85c82e4e918425, was
reverted.)

Introduce op trait PolyhedralScope for ops to define a new scope for
polyhedral optimization / affine dialect purposes, thus generalizing
such scopes beyond FuncOp. Ops to which this trait is attached will
define a new scope for the consideration of SSA values as valid symbols
for the purposes of polyhedral analysis and optimization. Update methods
that check for dim/symbol validity to work based on this trait.

Differential Revision: https://reviews.llvm.org/D79060

Added: 
    

Modified: 
    mlir/docs/Dialects/Affine.md
    mlir/docs/Traits.md
    mlir/include/mlir/Dialect/Affine/IR/AffineOps.h
    mlir/include/mlir/Dialect/Affine/IR/AffineOps.td
    mlir/include/mlir/IR/Function.h
    mlir/include/mlir/IR/Module.h
    mlir/include/mlir/IR/OpBase.td
    mlir/include/mlir/IR/OpDefinition.h
    mlir/lib/Dialect/Affine/IR/AffineOps.cpp
    mlir/test/Dialect/Affine/invalid.mlir
    mlir/test/Dialect/Affine/ops.mlir
    mlir/test/lib/Dialect/Test/TestDialect.cpp
    mlir/test/lib/Dialect/Test/TestOps.td

Removed: 
    


################################################################################
diff  --git a/mlir/docs/Dialects/Affine.md b/mlir/docs/Dialects/Affine.md
index 246c944f66fd..7eab93ace42e 100644
--- a/mlir/docs/Dialects/Affine.md
+++ b/mlir/docs/Dialects/Affine.md
@@ -60,20 +60,26 @@ Example:
 ### Restrictions on Dimensions and Symbols
 
 The affine dialect imposes certain restrictions on dimension and symbolic
-identifiers to enable powerful analysis and transformation. A symbolic
-identifier can be bound to an SSA value that is either an argument to the
-function, a value defined at the top level of that function (outside of all
-loops and if operations), the result of a
-[`constant` operation](Standard.md#constant-operation), or the result of an
-[`affine.apply` operation](#affineapply-operation) that recursively takes as
-arguments any symbolic identifiers, or the result of a [`dim`
-operation](Standard.md#dim-operation) on either a memref that is a function
-argument or a memref where the corresponding dimension is either static or a
-dynamic one in turn bound to a symbolic identifier.  Dimensions may be bound not
-only to anything that a symbol is bound to, but also to induction variables of
-enclosing [`affine.for`](#affinefor-affineforop) and
-[`affine.parallel`](#affineparallel-affineparallelop) operations, and the
-result of an
+identifiers to enable powerful analysis and transformation. An SSA value's use
+can be bound to a symbolic identifier if that SSA value is either
+1. a region argument for an op with trait `PolyhedralScope` (eg. `FuncOp`),
+2. a value defined at the top level of a `PolyhedralScope` op (i.e., immediately
+enclosed by the latter),
+3. a value that dominates the `PolyhedralScope` op enclosing the value's use,
+4. the result of a [`constant` operation](Standard.md#constant-operation),
+5. the result of an [`affine.apply`
+operation](#affineapply-operation) that recursively takes as arguments any valid
+symbolic identifiers, or
+6. the result of a [`dim` operation](Standard.md#dim-operation) on either a
+memref that is an argument to a `PolyhedralScope` op or a memref where the
+corresponding dimension is either static or a dynamic one in turn bound to a
+valid symbol.
+
+Note that as a result of rule (3) above, symbol validity is sensitive to the
+location of the SSA use.  Dimensions may be bound not only to anything that a
+symbol is bound to, but also to induction variables of enclosing
+[`affine.for`](#affinefor-operation) and
+[`affine.parallel`](#affineparallel-operation) operations, and the result of an
 [`affine.apply` operation](#affineapply-operation) (which recursively may use
 other dimensions and symbols).
 

diff  --git a/mlir/docs/Traits.md b/mlir/docs/Traits.md
index 5931fd3f9698..0281185abf91 100644
--- a/mlir/docs/Traits.md
+++ b/mlir/docs/Traits.md
@@ -219,6 +219,22 @@ foo.region_op {
 This trait is an important structural property of the IR, and enables operations
 to have [passes](PassManagement.md) scheduled under them.
 
+
+### PolyhedralScope
+
+*   `OpTrait::PolyhedralScope` -- `PolyhedralScope`
+
+This trait is carried by region holding operations that define a new scope for
+the purposes of polyhedral optimization and the affine dialect in particular.
+Any SSA values of 'index' type that either dominate such operations, or are
+defined at the top-level of such operations, or appear as region arguments for
+such operations automatically become valid symbols for the polyhedral scope
+defined by that operation. As a result, such SSA values could be used as the
+operands or index operands of various affine dialect operations like affine.for,
+affine.load, and affine.store.  The polyhedral scope defined by an operation
+with this trait includes all operations in its region excluding operations that
+are nested inside of other operations that themselves have this trait.
+
 ### Single Block with Implicit Terminator
 
 *   `OpTrait::SingleBlockImplicitTerminator<typename TerminatorOpType>` :

diff  --git a/mlir/include/mlir/Dialect/Affine/IR/AffineOps.h b/mlir/include/mlir/Dialect/Affine/IR/AffineOps.h
index cbbc2d76c46e..b0bba011eb6b 100644
--- a/mlir/include/mlir/Dialect/Affine/IR/AffineOps.h
+++ b/mlir/include/mlir/Dialect/Affine/IR/AffineOps.h
@@ -31,9 +31,10 @@ class AffineTerminatorOp;
 class FlatAffineConstraints;
 class OpBuilder;
 
-/// A utility function to check if a value is defined at the top level of a
-/// function. A value of index type defined at the top level is always a valid
-/// symbol.
+/// A utility function to check if a value is defined at the top level of an
+/// op with trait `PolyhedralScope` or is a region argument for such an op. A
+/// value of index type defined at the top level is always a valid symbol for
+/// all its uses.
 bool isTopLevelValue(Value value);
 
 /// AffineDmaStartOp starts a non-blocking DMA operation that transfers data
@@ -316,12 +317,22 @@ class AffineDmaWaitOp : public Op<AffineDmaWaitOp, OpTrait::VariadicOperands,
                      SmallVectorImpl<OpFoldResult> &results);
 };
 
-/// Returns true if the given Value can be used as a dimension id.
+/// Returns true if the given Value can be used as a dimension id in the region
+/// of the closest surrounding op that has the trait `PolyhedralScope`.
 bool isValidDim(Value value);
 
-/// Returns true if the given Value can be used as a symbol.
+/// Returns true if the given Value can be used as a dimension id in `region`,
+/// i.e., for all its uses in `region`.
+bool isValidDim(Value value, Region *region);
+
+/// Returns true if the given value can be used as a symbol in the region of the
+/// closest surrounding op that has the trait `PolyhedralScope`.
 bool isValidSymbol(Value value);
 
+/// Returns true if the given Value can be used as a symbol for `region`, i.e.,
+/// for all its uses in `region`.
+bool isValidSymbol(Value value, Region *region);
+
 /// Modifies both `map` and `operands` in-place so as to:
 /// 1. drop duplicate operands
 /// 2. drop unused dims and symbols from map

diff  --git a/mlir/include/mlir/Dialect/Affine/IR/AffineOps.td b/mlir/include/mlir/Dialect/Affine/IR/AffineOps.td
index c8f56539fafe..e2b7716fc334 100644
--- a/mlir/include/mlir/Dialect/Affine/IR/AffineOps.td
+++ b/mlir/include/mlir/Dialect/Affine/IR/AffineOps.td
@@ -83,12 +83,22 @@ def AffineApplyOp : Affine_Op<"apply", [NoSideEffect]> {
     /// Returns the affine value map computed from this operation.
     AffineValueMap getAffineValueMap();
 
-    /// Returns true if the result of this operation can be used as dimension id.
+    /// Returns true if the result of this operation can be used as dimension id
+    /// in the region of the closest surrounding op with trait PolyhedralScope.
     bool isValidDim();
 
-    /// Returns true if the result of this operation is a symbol.
+    /// Returns true if the result of this operation can be used as dimension id
+    /// within 'region', i.e., for all its uses with `region`.
+    bool isValidDim(Region *region);
+
+    /// Returns true if the result of this operation is a symbol in the region
+    /// of the closest surrounding op that has the trait PolyhedralScope.
     bool isValidSymbol();
 
+    /// Returns true if the result of this operation is a symbol for all its
+    /// uses in `region`.
+    bool isValidSymbol(Region *region);
+
     operand_range getMapOperands() { return getOperands(); }
   }];
 

diff  --git a/mlir/include/mlir/IR/Function.h b/mlir/include/mlir/IR/Function.h
index 9596b374a724..90b45910a2a3 100644
--- a/mlir/include/mlir/IR/Function.h
+++ b/mlir/include/mlir/IR/Function.h
@@ -30,10 +30,11 @@ namespace mlir {
 /// implicitly capture global values, and all external references must use
 /// Function arguments or attributes that establish a symbolic connection(e.g.
 /// symbols referenced by name via a string attribute).
-class FuncOp : public Op<FuncOp, OpTrait::ZeroOperands, OpTrait::ZeroResult,
-                         OpTrait::IsIsolatedFromAbove, OpTrait::FunctionLike,
-                         OpTrait::AutomaticAllocationScope,
-                         CallableOpInterface::Trait, SymbolOpInterface::Trait> {
+class FuncOp
+    : public Op<FuncOp, OpTrait::ZeroOperands, OpTrait::ZeroResult,
+                OpTrait::IsIsolatedFromAbove, OpTrait::FunctionLike,
+                OpTrait::AutomaticAllocationScope, OpTrait::PolyhedralScope,
+                CallableOpInterface::Trait, SymbolOpInterface::Trait> {
 public:
   using Op::Op;
   using Op::print;

diff  --git a/mlir/include/mlir/IR/Module.h b/mlir/include/mlir/IR/Module.h
index 4f0bba773ee2..e724dd034030 100644
--- a/mlir/include/mlir/IR/Module.h
+++ b/mlir/include/mlir/IR/Module.h
@@ -30,7 +30,8 @@ class ModuleTerminatorOp;
 class ModuleOp
     : public Op<
           ModuleOp, OpTrait::ZeroOperands, OpTrait::ZeroResult,
-          OpTrait::IsIsolatedFromAbove, OpTrait::SymbolTable,
+          OpTrait::IsIsolatedFromAbove, OpTrait::PolyhedralScope,
+          OpTrait::SymbolTable,
           OpTrait::SingleBlockImplicitTerminator<ModuleTerminatorOp>::Impl,
           SymbolOpInterface::Trait> {
 public:

diff  --git a/mlir/include/mlir/IR/OpBase.td b/mlir/include/mlir/IR/OpBase.td
index 3e55eadfd742..087aecb6b35d 100644
--- a/mlir/include/mlir/IR/OpBase.td
+++ b/mlir/include/mlir/IR/OpBase.td
@@ -1648,6 +1648,8 @@ def ConstantLike : NativeOpTrait<"ConstantLike">;
 def FunctionLike : NativeOpTrait<"FunctionLike">;
 // Op is isolated from above.
 def IsolatedFromAbove : NativeOpTrait<"IsIsolatedFromAbove">;
+// Op defines a polyhedral scope.
+def PolyhedralScope : NativeOpTrait<"PolyhedralScope">;
 // Op results are float or vectors/tensors thereof.
 def ResultsAreFloatLike : NativeOpTrait<"ResultsAreFloatLike">;
 // Op has the same operand type.

diff  --git a/mlir/include/mlir/IR/OpDefinition.h b/mlir/include/mlir/IR/OpDefinition.h
index 107234a7158e..5dc481d1df2b 100644
--- a/mlir/include/mlir/IR/OpDefinition.h
+++ b/mlir/include/mlir/IR/OpDefinition.h
@@ -1034,6 +1034,21 @@ class IsIsolatedFromAbove
   }
 };
 
+/// A trait of region holding operations that defines a new scope for polyhedral
+/// optimization purposes. Any SSA values of 'index' type that either dominate
+/// such an operation or are used at the top-level of such an operation
+/// automatically become valid symbols for the polyhedral scope defined by that
+/// operation. For more details, see `Traits.md#PolyhedralScope`.
+template <typename ConcreteType>
+class PolyhedralScope : public TraitBase<ConcreteType, PolyhedralScope> {
+public:
+  static LogicalResult verifyTrait(Operation *op) {
+    static_assert(!ConcreteType::template hasTrait<ZeroRegion>(),
+                  "expected operation to have one or more regions");
+    return success();
+  }
+};
+
 /// A trait of region holding operations that define a new scope for automatic
 /// allocations, i.e., allocations that are freed when control is transferred
 /// back from the operation's region. Any operations performing such allocations

diff  --git a/mlir/lib/Dialect/Affine/IR/AffineOps.cpp b/mlir/lib/Dialect/Affine/IR/AffineOps.cpp
index 0ea1f8dc84e7..8f533e9b2177 100644
--- a/mlir/lib/Dialect/Affine/IR/AffineOps.cpp
+++ b/mlir/lib/Dialect/Affine/IR/AffineOps.cpp
@@ -84,65 +84,110 @@ Operation *AffineDialect::materializeConstant(OpBuilder &builder,
   return builder.create<ConstantOp>(loc, type, value);
 }
 
-/// A utility function to check if a given region is attached to a function.
-static bool isFunctionRegion(Region *region) {
-  return llvm::isa<FuncOp>(region->getParentOp());
+/// A utility function to check if a value is defined at the top level of an
+/// op with trait `PolyhedralScope`. A value of index type defined at the top
+/// level is always a valid symbol.
+bool mlir::isTopLevelValue(Value value) {
+  if (auto arg = value.dyn_cast<BlockArgument>())
+    return arg.getOwner()->getParentOp()->hasTrait<OpTrait::PolyhedralScope>();
+  return value.getDefiningOp()
+      ->getParentOp()
+      ->hasTrait<OpTrait::PolyhedralScope>();
 }
 
-/// A utility function to check if a value is defined at the top level of a
-/// function. A value of index type defined at the top level is always a valid
-/// symbol.
-bool mlir::isTopLevelValue(Value value) {
+/// A utility function to check if a value is defined at the top level of
+/// `region` or is an argument of `region`. A value of index type defined at the
+/// top level of a `PolyhedralScope` region is always a valid symbol for all
+/// uses in that region.
+static bool isTopLevelValue(Value value, Region *region) {
   if (auto arg = value.dyn_cast<BlockArgument>())
-    return isFunctionRegion(arg.getOwner()->getParent());
-  return isFunctionRegion(value.getDefiningOp()->getParentRegion());
+    return arg.getParentRegion() == region;
+  return value.getDefiningOp()->getParentOp() == region->getParentOp();
+}
+
+/// Returns the closest region enclosing `op` that is held by an operation with
+/// trait `PolyhedralScope`.
+//  TODO: getAffineScope should be publicly exposed for affine passes/utilities.
+static Region *getAffineScope(Operation *op) {
+  auto *curOp = op;
+  while (auto *parentOp = curOp->getParentOp()) {
+    if (parentOp->hasTrait<OpTrait::PolyhedralScope>())
+      return curOp->getParentRegion();
+    curOp = parentOp;
+  }
+  llvm_unreachable("op doesn't have an enclosing polyhedral scope");
 }
 
-// Value can be used as a dimension id if it is valid as a symbol, or
-// it is an induction variable, or it is a result of affine apply operation
-// with dimension id arguments.
+// A Value can be used as a dimension id iff it meets one of the following
+// conditions:
+// *) It is valid as a symbol.
+// *) It is an induction variable.
+// *) It is the result of affine apply operation with dimension id arguments.
 bool mlir::isValidDim(Value value) {
   // The value must be an index type.
   if (!value.getType().isIndex())
     return false;
 
-  if (auto *op = value.getDefiningOp()) {
-    // Top level operation or constant operation is ok.
-    if (isFunctionRegion(op->getParentRegion()) || isa<ConstantOp>(op))
-      return true;
-    // Affine apply operation is ok if all of its operands are ok.
-    if (auto applyOp = dyn_cast<AffineApplyOp>(op))
-      return applyOp.isValidDim();
-    // The dim op is okay if its operand memref/tensor is defined at the top
-    // level.
-    if (auto dimOp = dyn_cast<DimOp>(op))
-      return isTopLevelValue(dimOp.getOperand());
+  if (auto *defOp = value.getDefiningOp())
+    return isValidDim(value, getAffineScope(defOp));
+
+  // This value has to be a block argument for an op that has the
+  // `PolyhedralScope` trait or for an affine.for or affine.parallel.
+  auto *parentOp = value.cast<BlockArgument>().getOwner()->getParentOp();
+  return parentOp->hasTrait<OpTrait::PolyhedralScope>() ||
+         isa<AffineForOp>(parentOp) || isa<AffineParallelOp>(parentOp);
+}
+
+// Value can be used as a dimension id iff it meets one of the following
+// conditions:
+// *) It is valid as a symbol.
+// *) It is an induction variable.
+// *) It is the result of an affine apply operation with dimension id operands.
+bool mlir::isValidDim(Value value, Region *region) {
+  // The value must be an index type.
+  if (!value.getType().isIndex())
     return false;
+
+  // All valid symbols are okay.
+  if (isValidSymbol(value, region))
+    return true;
+
+  auto *op = value.getDefiningOp();
+  if (!op) {
+    // This value has to be a block argument for an affine.for or an
+    // affine.parallel.
+    auto *parentOp = value.cast<BlockArgument>().getOwner()->getParentOp();
+    return isa<AffineForOp>(parentOp) || isa<AffineParallelOp>(parentOp);
   }
-  // This value has to be a block argument of a FuncOp, an 'affine.for', or an
-  // 'affine.parallel'.
-  auto *parentOp = value.cast<BlockArgument>().getOwner()->getParentOp();
-  return isa<FuncOp>(parentOp) || isa<AffineForOp>(parentOp) ||
-         isa<AffineParallelOp>(parentOp);
+
+  // Affine apply operation is ok if all of its operands are ok.
+  if (auto applyOp = dyn_cast<AffineApplyOp>(op))
+    return applyOp.isValidDim(region);
+  // The dim op is okay if its operand memref/tensor is defined at the top
+  // level.
+  if (auto dimOp = dyn_cast<DimOp>(op))
+    return isTopLevelValue(dimOp.getOperand());
+  return false;
 }
 
 /// Returns true if the 'index' dimension of the `memref` defined by
-/// `memrefDefOp` is a statically  shaped one or defined using a valid symbol.
+/// `memrefDefOp` is a statically  shaped one or defined using a valid symbol
+/// for `region`.
 template <typename AnyMemRefDefOp>
-static bool isMemRefSizeValidSymbol(AnyMemRefDefOp memrefDefOp,
-                                    unsigned index) {
+bool isMemRefSizeValidSymbol(AnyMemRefDefOp memrefDefOp, unsigned index,
+                             Region *region) {
   auto memRefType = memrefDefOp.getType();
   // Statically shaped.
   if (!memRefType.isDynamicDim(index))
     return true;
   // Get the position of the dimension among dynamic dimensions;
   unsigned dynamicDimPos = memRefType.getDynamicDimIndex(index);
-  return isValidSymbol(
-      *(memrefDefOp.getDynamicSizes().begin() + dynamicDimPos));
+  return isValidSymbol(*(memrefDefOp.getDynamicSizes().begin() + dynamicDimPos),
+                       region);
 }
 
-/// Returns true if the result of the dim op is a valid symbol.
-static bool isDimOpValidSymbol(DimOp dimOp) {
+/// Returns true if the result of the dim op is a valid symbol for `region`.
+static bool isDimOpValidSymbol(DimOp dimOp, Region *region) {
   // The dim op is okay if its operand memref/tensor is defined at the top
   // level.
   if (isTopLevelValue(dimOp.getOperand()))
@@ -152,43 +197,90 @@ static bool isDimOpValidSymbol(DimOp dimOp) {
   // whose corresponding size is a valid symbol.
   unsigned index = dimOp.getIndex();
   if (auto viewOp = dyn_cast<ViewOp>(dimOp.getOperand().getDefiningOp()))
-    return isMemRefSizeValidSymbol<ViewOp>(viewOp, index);
+    return isMemRefSizeValidSymbol<ViewOp>(viewOp, index, region);
   if (auto subViewOp = dyn_cast<SubViewOp>(dimOp.getOperand().getDefiningOp()))
-    return isMemRefSizeValidSymbol<SubViewOp>(subViewOp, index);
+    return isMemRefSizeValidSymbol<SubViewOp>(subViewOp, index, region);
   if (auto allocOp = dyn_cast<AllocOp>(dimOp.getOperand().getDefiningOp()))
-    return isMemRefSizeValidSymbol<AllocOp>(allocOp, index);
+    return isMemRefSizeValidSymbol<AllocOp>(allocOp, index, region);
   return false;
 }
 
-// Value can be used as a symbol if it is a constant, or it is defined at
-// the top level, or it is a result of affine apply operation with symbol
-// arguments, or a result of the dim op on a memref satisfying certain
-// constraints.
+// A value can be used as a symbol (at all its use sites) iff it meets one of
+// the following conditions:
+// *) It is a constant.
+// *) Its defining op or block arg appearance is immediately enclosed by an op
+//    with `PolyhedralScope` trait.
+// *) It is the result of an affine.apply operation with symbol operands.
+// *) It is a result of the dim op on a memref whose corresponding size is a
+//    valid symbol.
 bool mlir::isValidSymbol(Value value) {
   // The value must be an index type.
   if (!value.getType().isIndex())
     return false;
 
-  if (auto *op = value.getDefiningOp()) {
-    // Top level operation or constant operation is ok.
-    if (isFunctionRegion(op->getParentRegion()) || isa<ConstantOp>(op))
-      return true;
-    // Affine apply operation is ok if all of its operands are ok.
-    if (auto applyOp = dyn_cast<AffineApplyOp>(op))
-      return applyOp.isValidSymbol();
-    if (auto dimOp = dyn_cast<DimOp>(op)) {
-      return isDimOpValidSymbol(dimOp);
-    }
+  // Check that the value is a top level value.
+  if (isTopLevelValue(value))
+    return true;
+
+  if (auto *defOp = value.getDefiningOp())
+    return isValidSymbol(value, getAffineScope(defOp));
+
+  return false;
+}
+
+// A value can be used as a symbol for `region` iff it meets onf of the the
+// following conditions:
+// *) It is a constant.
+// *) It is defined at the top level of 'region' or is its argument.
+// *) It dominates `region`'s parent op.
+// *) It is the result of an affine apply operation with symbol arguments.
+// *) It is a result of the dim op on a memref whose corresponding size is
+//    a valid symbol.
+bool mlir::isValidSymbol(Value value, Region *region) {
+  // The value must be an index type.
+  if (!value.getType().isIndex())
+    return false;
+
+  // A top-level value is a valid symbol.
+  if (::isTopLevelValue(value, region))
+    return true;
+
+  auto *defOp = value.getDefiningOp();
+  if (!defOp) {
+    // A block argument that is not a top-level value is a valid symbol if it
+    // dominates region's parent op.
+    if (!region->getParentOp()->isKnownIsolatedFromAbove())
+      if (auto *parentOpRegion = region->getParentOp()->getParentRegion())
+        return isValidSymbol(value, parentOpRegion);
+    return false;
   }
-  // Otherwise, check that the value is a top level value.
-  return isTopLevelValue(value);
+
+  // Constant operation is ok.
+  Attribute operandCst;
+  if (matchPattern(defOp, m_Constant(&operandCst)))
+    return true;
+
+  // Affine apply operation is ok if all of its operands are ok.
+  if (auto applyOp = dyn_cast<AffineApplyOp>(defOp))
+    return applyOp.isValidSymbol(region);
+
+  // Dim op results could be valid symbols at any level.
+  if (auto dimOp = dyn_cast<DimOp>(defOp))
+    return isDimOpValidSymbol(dimOp, region);
+
+  // Check for values dominating `region`'s parent op.
+  if (!region->getParentOp()->isKnownIsolatedFromAbove())
+    if (auto *parentRegion = region->getParentOp()->getParentRegion())
+      return isValidSymbol(value, parentRegion);
+
+  return false;
 }
 
 // Returns true if 'value' is a valid index to an affine operation (e.g.
-// affine.load, affine.store, affine.dma_start, affine.dma_wait).
-// Returns false otherwise.
-static bool isValidAffineIndexOperand(Value value) {
-  return isValidDim(value) || isValidSymbol(value);
+// affine.load, affine.store, affine.dma_start, affine.dma_wait) where
+// `region` provides the polyhedral symbol scope. Returns false otherwise.
+static bool isValidAffineIndexOperand(Value value, Region *region) {
+  return isValidDim(value, region) || isValidSymbol(value, region);
 }
 
 /// Utility function to verify that a set of operands are valid dimension and
@@ -203,9 +295,9 @@ verifyDimAndSymbolIdentifiers(OpTy &op, Operation::operand_range operands,
   unsigned opIt = 0;
   for (auto operand : operands) {
     if (opIt++ < numDims) {
-      if (!isValidDim(operand))
+      if (!isValidDim(operand, getAffineScope(op)))
         return op.emitOpError("operand cannot be used as a dimension id");
-    } else if (!isValidSymbol(operand)) {
+    } else if (!isValidSymbol(operand, getAffineScope(op))) {
       return op.emitOpError("operand cannot be used as a symbol");
     }
   }
@@ -273,6 +365,14 @@ bool AffineApplyOp::isValidDim() {
                       [](Value op) { return mlir::isValidDim(op); });
 }
 
+// The result of the affine apply operation can be used as a dimension id if all
+// its operands are valid dimension ids with the parent operation of `region`
+// defining the polyhedral scope for symbols.
+bool AffineApplyOp::isValidDim(Region *region) {
+  return llvm::all_of(getOperands(),
+                      [&](Value op) { return ::isValidDim(op, region); });
+}
+
 // The result of the affine apply operation can be used as a symbol if all its
 // operands are symbols.
 bool AffineApplyOp::isValidSymbol() {
@@ -280,6 +380,14 @@ bool AffineApplyOp::isValidSymbol() {
                       [](Value op) { return mlir::isValidSymbol(op); });
 }
 
+// The result of the affine apply operation can be used as a symbol in `region`
+// if all its operands are symbols in `region`.
+bool AffineApplyOp::isValidSymbol(Region *region) {
+  return llvm::all_of(getOperands(), [&](Value operand) {
+    return mlir::isValidSymbol(operand, region);
+  });
+}
+
 OpFoldResult AffineApplyOp::fold(ArrayRef<Attribute> operands) {
   auto map = getAffineMap();
 
@@ -948,22 +1056,23 @@ LogicalResult AffineDmaStartOp::verify() {
     return emitOpError("incorrect number of operands");
   }
 
+  Region *scope = getAffineScope(*this);
   for (auto idx : getSrcIndices()) {
     if (!idx.getType().isIndex())
       return emitOpError("src index to dma_start must have 'index' type");
-    if (!isValidAffineIndexOperand(idx))
+    if (!isValidAffineIndexOperand(idx, scope))
       return emitOpError("src index must be a dimension or symbol identifier");
   }
   for (auto idx : getDstIndices()) {
     if (!idx.getType().isIndex())
       return emitOpError("dst index to dma_start must have 'index' type");
-    if (!isValidAffineIndexOperand(idx))
+    if (!isValidAffineIndexOperand(idx, scope))
       return emitOpError("dst index must be a dimension or symbol identifier");
   }
   for (auto idx : getTagIndices()) {
     if (!idx.getType().isIndex())
       return emitOpError("tag index to dma_start must have 'index' type");
-    if (!isValidAffineIndexOperand(idx))
+    if (!isValidAffineIndexOperand(idx, scope))
       return emitOpError("tag index must be a dimension or symbol identifier");
   }
   return success();
@@ -1036,10 +1145,11 @@ ParseResult AffineDmaWaitOp::parse(OpAsmParser &parser,
 LogicalResult AffineDmaWaitOp::verify() {
   if (!getOperand(0).getType().isa<MemRefType>())
     return emitOpError("expected DMA tag to be of memref type");
+  Region *scope = getAffineScope(*this);
   for (auto idx : getTagIndices()) {
     if (!idx.getType().isIndex())
       return emitOpError("index to dma_wait must have 'index' type");
-    if (!isValidAffineIndexOperand(idx))
+    if (!isValidAffineIndexOperand(idx, scope))
       return emitOpError("index must be a dimension or symbol identifier");
   }
   return success();
@@ -1814,10 +1924,11 @@ LogicalResult verify(AffineLoadOp op) {
           "expects the number of subscripts to be equal to memref rank");
   }
 
+  Region *scope = getAffineScope(op);
   for (auto idx : op.getMapOperands()) {
     if (!idx.getType().isIndex())
       return op.emitOpError("index to load must have 'index' type");
-    if (!isValidAffineIndexOperand(idx))
+    if (!isValidAffineIndexOperand(idx, scope))
       return op.emitOpError("index must be a dimension or symbol identifier");
   }
   return success();
@@ -1914,10 +2025,11 @@ LogicalResult verify(AffineStoreOp op) {
           "expects the number of subscripts to be equal to memref rank");
   }
 
+  Region *scope = getAffineScope(op);
   for (auto idx : op.getMapOperands()) {
     if (!idx.getType().isIndex())
       return op.emitOpError("index to store must have 'index' type");
-    if (!isValidAffineIndexOperand(idx))
+    if (!isValidAffineIndexOperand(idx, scope))
       return op.emitOpError("index must be a dimension or symbol identifier");
   }
   return success();
@@ -2136,8 +2248,9 @@ static LogicalResult verify(AffinePrefetchOp op) {
       return op.emitOpError("too few operands");
   }
 
+  Region *scope = getAffineScope(op);
   for (auto idx : op.getMapOperands()) {
-    if (!isValidAffineIndexOperand(idx))
+    if (!isValidAffineIndexOperand(idx, scope))
       return op.emitOpError("index must be a dimension or symbol identifier");
   }
   return success();

diff  --git a/mlir/test/Dialect/Affine/invalid.mlir b/mlir/test/Dialect/Affine/invalid.mlir
index 4ad8b7ed8247..c0855987ac32 100644
--- a/mlir/test/Dialect/Affine/invalid.mlir
+++ b/mlir/test/Dialect/Affine/invalid.mlir
@@ -124,7 +124,7 @@ func @affine_if_invalid_dimop_dim(%arg0: index, %arg1: index, %arg2: index, %arg
     %0 = alloc(%arg0, %arg1, %arg2, %arg3) : memref<?x?x?x?xf32>
     %dim = dim %0, 0 : memref<?x?x?x?xf32>
 
-    // expected-error at +1 {{operand cannot be used as a dimension id}}
+    // expected-error at +1 {{operand cannot be used as a symbol}}
     affine.if #set0(%dim)[%n0] {}
   }
   return

diff  --git a/mlir/test/Dialect/Affine/ops.mlir b/mlir/test/Dialect/Affine/ops.mlir
index cd42980f87c9..d4b3a112dfc6 100644
--- a/mlir/test/Dialect/Affine/ops.mlir
+++ b/mlir/test/Dialect/Affine/ops.mlir
@@ -115,6 +115,44 @@ func @valid_symbols(%arg0: index, %arg1: index, %arg2: index) {
 
 // -----
 
+// Test symbol constraints for ops with PolyhedralScope trait.
+
+// CHECK-LABEL: func @valid_symbol_polyhedral_scope
+func @valid_symbol_polyhedral_scope(%n : index, %A : memref<?xf32>) {
+  test.polyhedral_scope {
+    %c1 = constant 1 : index
+    %l = subi %n, %c1 : index
+    // %l, %n are valid symbols since test.polyhedral_scope defines a new
+    // polyhedral scope.
+    affine.for %i = %l to %n {
+      %m = subi %l, %i : index
+      test.polyhedral_scope {
+        // %m and %n are valid symbols.
+        affine.for %j = %m to %n {
+          %v = affine.load %A[%n - 1] : memref<?xf32>
+          affine.store %v, %A[%n - 1] : memref<?xf32>
+        }
+        "terminate"() : () -> ()
+      }
+    }
+    "terminate"() : () -> ()
+  }
+  return
+}
+
+// -----
+
+// Test the fact that module op always provides a polyhedral scope.
+
+%idx = "test.foo"() : () -> (index)
+"test.func"() ({
+^bb0(%A : memref<?xf32>):
+  affine.load %A[%idx] : memref<?xf32>
+  "terminate"() : () -> ()
+}) : () -> ()
+
+// -----
+
 // CHECK-LABEL: @parallel
 // CHECK-SAME: (%[[N:.*]]: index)
 func @parallel(%N : index) {

diff  --git a/mlir/test/lib/Dialect/Test/TestDialect.cpp b/mlir/test/lib/Dialect/Test/TestDialect.cpp
index 048db3a2fcbd..4c67310e3705 100644
--- a/mlir/test/lib/Dialect/Test/TestDialect.cpp
+++ b/mlir/test/lib/Dialect/Test/TestDialect.cpp
@@ -201,6 +201,22 @@ static void print(OpAsmPrinter &p, IsolatedRegionOp op) {
   p.printRegion(op.region(), /*printEntryBlockArgs=*/false);
 }
 
+//===----------------------------------------------------------------------===//
+// Test PolyhedralScopeOp
+//===----------------------------------------------------------------------===//
+
+static ParseResult parsePolyhedralScopeOp(OpAsmParser &parser,
+                                          OperationState &result) {
+  // Parse the body region, and reuse the operand info as the argument info.
+  Region *body = result.addRegion();
+  return parser.parseRegion(*body, /*arguments=*/{}, /*argTypes=*/{});
+}
+
+static void print(OpAsmPrinter &p, PolyhedralScopeOp op) {
+  p << "test.polyhedral_scope ";
+  p.printRegion(op.region(), /*printEntryBlockArgs=*/false);
+}
+
 //===----------------------------------------------------------------------===//
 // Test parser.
 //===----------------------------------------------------------------------===//

diff  --git a/mlir/test/lib/Dialect/Test/TestOps.td b/mlir/test/lib/Dialect/Test/TestOps.td
index 8fb290a76e13..f9140f2e9bdc 100644
--- a/mlir/test/lib/Dialect/Test/TestOps.td
+++ b/mlir/test/lib/Dialect/Test/TestOps.td
@@ -9,6 +9,7 @@
 #ifndef TEST_OPS
 #define TEST_OPS
 
+include "mlir/Dialect/Affine/IR/AffineOpsBase.td"
 include "mlir/IR/OpBase.td"
 include "mlir/IR/OpAsmInterface.td"
 include "mlir/IR/SymbolInterfaces.td"
@@ -1138,6 +1139,17 @@ def IsolatedRegionOp : TEST_Op<"isolated_region", [IsolatedFromAbove]> {
   let printer = [{ return ::print(p, *this); }];
 }
 
+def PolyhedralScopeOp : TEST_Op<"polyhedral_scope", [PolyhedralScope]> {
+  let summary =  "polyhedral scope operation";
+  let description = [{
+    Test op that defines a new polyhedral scope.
+  }];
+
+  let regions = (region SizedRegion<1>:$region);
+  let parser = [{ return ::parse$cppClass(parser, result); }];
+  let printer = [{ return ::print(p, *this); }];
+}
+
 def WrappingRegionOp : TEST_Op<"wrapping_region",
     [SingleBlockImplicitTerminator<"TestReturnOp">]> {
   let summary =  "wrapping region operation";


        


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