[mlir][Interfaces] Clean up DestinationStyleOpInterface

* "init" operands are specified with `MutableOperandRange` (which gives access to the underlying `OpOperand *`). No more magic numbers.
* Remove most interface methods and make them helper functions. Only `getInitsMutable` should be implemented.
* Provide separate helper functions for accessing mutable/immutable operands (`OpOperand`/`Value`, in line with #66515): `getInitsMutable` and `getInits` (same naming convention as auto-generated op accessors). `getInputOperands` was not renamed because this function cannot return a `MutableOperandRange` (because the operands are not necessarily consecutive). `OpOperandVector` is no longer needed.
* The new `getDpsInits`/`getDpsInitsMutable` is more efficient than the old `getDpsInitOperands` because no `SmallVector` is created. The new functions return a range of operands.
* Fix a bug in `getDpsInputOperands`: out-of-bounds operands were potentially returned.

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mlir/include/mlir/Dialect/Bufferization/IR/BufferizationOps.td

@@ -264,9 +264,7 @@ def Bufferization_MaterializeInDestinationOp
       return ::llvm::cast<RankedTensorType>(getResult().getType());
     }
 
-    std::pair<int64_t, int64_t> getDpsInitsPositionRange() {
-      return {1, 2};  // `dest` operand
-    }
+    MutableOperandRange getDpsInitsMutable() { return getDestMutable(); }
   }];
 
   let assemblyFormat = "$source `in` $dest attr-dict `:` type($source)";

mlir/include/mlir/Dialect/Linalg/IR/LinalgInterfaces.td

@@ -555,12 +555,12 @@ def LinalgStructuredInterface
         are expection. For example, in `map` output operand isn't used in
         the block.
       }],
-      /*retTy=*/"OpOperandVector",
+      /*retTy=*/"::llvm::SmallVector<OpOperand *>",
       /*methodName=*/"getOpOperandsMatchingBBargs",
       /*args=*/(ins),
       /*methodBody=*/"",
       /*defaultImplementation=*/[{
-        OpOperandVector result;
+        ::llvm::SmallVector<OpOperand *> result;
         result.reserve($_op->getNumOperands());
         llvm::transform(
           this->getOperation()->getOpOperands(),

mlir/include/mlir/Dialect/Linalg/IR/LinalgOps.td

@@ -149,14 +149,7 @@ def Linalg_SoftmaxOp : Linalg_Op<"softmax",
     int64_t getOutputOperandRank() {
       return getOutputOperandType().getRank();
     }
-    // Method to implement DestinationStyleOpInterface.
-    std::pair<int64_t, int64_t> getDpsInitsPositionRange() {
-      std::pair<unsigned, unsigned> outputsIndexAndLength =
-        getODSOperandIndexAndLength(1);
-      return std::make_pair<int64_t, int64_t>(
-          outputsIndexAndLength.first,
-          outputsIndexAndLength.first + outputsIndexAndLength.second);
-    }
+    MutableOperandRange getDpsInitsMutable() { return getOutputMutable(); }
   }];
   let hasVerifier = 1;
 }

mlir/include/mlir/Dialect/Linalg/IR/LinalgStructuredOps.td

@@ -207,10 +207,8 @@ def GenericOp : LinalgStructuredBase_Op<"generic", [
     getRegionBuilder() {
       return nullptr;
     }
-    std::pair<int64_t, int64_t> getDpsInitsPositionRange() {
-      int64_t getNumOperands = this->getNumOperands();
-      return {getNumOperands - getOutputs().size(), getNumOperands};
-    }
+
+    MutableOperandRange getDpsInitsMutable() { return getOutputsMutable(); }
   }];
 
   let hasCanonicalizer = 1;
@@ -283,11 +281,9 @@ def MapOp : LinalgStructuredBase_Op<"map", [
     }
 
     // Implement functions necessary for DestinationStyleOpInterface.
-    std::pair<int64_t, int64_t> getDpsInitsPositionRange() {
-      int64_t getNumOperands = this->getNumOperands();
-      return {getNumOperands - 1, getNumOperands};
-    }
-    OpOperandVector getOpOperandsMatchingBBargs() {
+    MutableOperandRange getDpsInitsMutable() { return getInitMutable(); }
+
+    SmallVector<OpOperand *> getOpOperandsMatchingBBargs() {
       return getDpsInputOperands();
     }
 
@@ -381,9 +377,7 @@ def ReduceOp : LinalgStructuredBase_Op<"reduce", [
     getRegionBuilder() {
       return nullptr;
     }
-    std::pair<int64_t, int64_t> getDpsInitsPositionRange() {
-      return {getInits().size(), getNumOperands()};
-    }
+    MutableOperandRange getDpsInitsMutable() { return getInitsMutable(); }
   }];
 
   let hasCustomAssemblyFormat = 1;
@@ -446,10 +440,7 @@ def TransposeOp : LinalgStructuredBase_Op<"transpose", [
     }
 
     // Implement functions necessary for DestinationStyleOpInterface.
-    std::pair<int64_t, int64_t> getDpsInitsPositionRange() {
-      int64_t getNumOperands = this->getNumOperands();
-      return {getNumOperands - 1, getNumOperands};
-    }
+    MutableOperandRange getDpsInitsMutable() { return getInitMutable(); }
 
     static std::function<void(mlir::ImplicitLocOpBuilder &, mlir::Block &,
         mlir::ArrayRef<mlir::NamedAttribute>)>
@@ -517,10 +508,7 @@ def BroadcastOp : LinalgStructuredBase_Op<"broadcast", [
     }
 
     // Implement functions necessary for DestinationStyleOpInterface.
-    std::pair<int64_t, int64_t> getDpsInitsPositionRange() {
-      int64_t getNumOperands = this->getNumOperands();
-      return {getNumOperands - 1, getNumOperands};
-    }
+    MutableOperandRange getDpsInitsMutable() { return getInitMutable(); }
 
     static std::function<void(mlir::ImplicitLocOpBuilder &, mlir::Block &,
         mlir::ArrayRef<mlir::NamedAttribute>)>

mlir/include/mlir/Dialect/Tensor/IR/TensorOps.td

@@ -750,9 +750,7 @@ def Tensor_InsertOp : Tensor_Op<"insert", [
   }];
 
   let extraClassDeclaration = [{
-    std::pair<int64_t, int64_t> getDpsInitsPositionRange() {
-      return {1, 2};  // `dest` operand
-    }
+    MutableOperandRange getDpsInitsMutable() { return getDestMutable(); }
   }];
 
   let hasFolder = 1;
@@ -892,9 +890,7 @@ def Tensor_InsertSliceOp : Tensor_OpWithOffsetSizesAndStrides<"insert_slice", [
     /// and `strides` operands.
     static unsigned getOffsetSizeAndStrideStartOperandIndex() { return 2; }
 
-    std::pair<int64_t, int64_t> getDpsInitsPositionRange() {
-      return {1, 2};  // `dest` operand
-    }
+    MutableOperandRange getDpsInitsMutable() { return getDestMutable(); }
   }];
 
   let hasCanonicalizer = 1;
@@ -1714,10 +1710,7 @@ class Tensor_RelayoutOp<string mnemonic, list<Trait> traits = []> :
     RankedTensorType getDestType() {
       return ::llvm::cast<RankedTensorType>(getDest().getType()); };
 
-    /// Return position for init operand. Init operand is `dest`.
-    std::pair<int64_t, int64_t> getDpsInitsPositionRange() {
-      return {1, 2}; // `dest` operand
-    }
+    MutableOperandRange getDpsInitsMutable() { return getDestMutable(); }
 
     /// Interface method for ConditionallySpeculatable.
     Speculation::Speculatability getSpeculatability();

mlir/include/mlir/Dialect/Vector/IR/VectorOps.td

@@ -1330,8 +1330,8 @@ def Vector_TransferReadOp :
     // MaskableOpInterface methods.
     bool supportsPassthru() { return true; }
 
-    std::pair<int64_t, int64_t> getDpsInitsPositionRange() {
-      return {0, 0};  // empty range (no init operands)
+    MutableOperandRange getDpsInitsMutable() {
+      return MutableOperandRange(getOperation(), /*start=*/0, /*length=*/0);
     }
   }];
 
@@ -1494,9 +1494,7 @@ def Vector_TransferWriteOp :
     ///  ops of other dialects.
     Value getValue() { return getVector(); }
 
-    std::pair<int64_t, int64_t> getDpsInitsPositionRange() {
-      return {1, 2};  // `source` operand
-    }
+    MutableOperandRange getDpsInitsMutable() { return getSourceMutable(); }
   }];
 
   let hasFolder = 1;

mlir/include/mlir/Interfaces/DestinationStyleOpInterface.h

@@ -17,11 +17,6 @@
 #include "llvm/ADT/SmallVector.h"
 
 namespace mlir {
-/// OpOperand vector that implicitly converts to a Value vector.
-struct OpOperandVector : public llvm::SmallVector<OpOperand *> {
-  operator SmallVector<Value>();
-};
-
 namespace detail {
 /// Verify that `op` conforms to the invariants of DestinationStyleOpInterface
 LogicalResult verifyDestinationStyleOpInterface(Operation *op);