[mlir][IR] Change MutableOperandRange::operator[] to return an OpOperand & (llvm#66515)

`operator[]` returns `OpOperand &` instead of `Value`.

* This allows users to get OpOperands by name instead of "magic" number.
E.g., `extractSliceOp->getOpOperand(0)` can be written as
`extractSliceOp.getSourceMutable()[0]`.
* `OperandRange` provides a read-only API to operands: `operator[]`
returns `Value`. `MutableOperandRange` now provides a mutable API:
`operator[]` returns `OpOperand &`, which can be used to set operands.

Note: The TableGen code generator could be changed to return `OpOperand
&` (instead of `MutableOperandRange`) for non-variadic and non-optional
arguments in a subsequent change. Then the `[0]` part in the above
example would no longer be necessary.

Author: matthias-springer

mlir/include/mlir/IR/ValueRange.h

@@ -162,10 +162,8 @@ class MutableOperandRange {
   /// elements attribute, which contains the sizes of the sub ranges.
   MutableOperandRangeRange split(NamedAttribute segmentSizes) const;
 
-  /// Returns the value at the given index.
-  Value operator[](unsigned index) const {
-    return operator OperandRange()[index];
-  }
+  /// Returns the OpOperand at the given index.
+  OpOperand &operator[](unsigned index) const;
 
   OperandRange::iterator begin() const {
     return static_cast<OperandRange>(*this).begin();

mlir/include/mlir/Interfaces/ControlFlowInterfaces.h

@@ -76,7 +76,7 @@ class SuccessorOperands {
   Value operator[](unsigned index) const {
     if (isOperandProduced(index))
       return Value();
-    return forwardedOperands[index - producedOperandCount];
+    return forwardedOperands[index - producedOperandCount].get();
   }
 
   /// Get the range of operands that are simply forwarded to the successor.

mlir/lib/Dialect/Bufferization/IR/BufferizationOps.cpp

@@ -549,22 +549,18 @@ LogicalResult DeallocTensorOp::bufferize(RewriterBase &rewriter,
 
 bool MaterializeInDestinationOp::bufferizesToMemoryRead(
     OpOperand &opOperand, const AnalysisState &state) {
-  if (&opOperand == &getOperation()->getOpOperand(0) /*source*/)
-    return true;
-  return false;
+  return &opOperand == &getSourceMutable()[0];
 }
 
 bool MaterializeInDestinationOp::bufferizesToMemoryWrite(
     OpOperand &opOperand, const AnalysisState &state) {
-  if (&opOperand == &getOperation()->getOpOperand(1) /*dest*/)
-    return true;
-  return false;
+  return &opOperand == &getDestMutable()[0];
 }
 
 AliasingValueList
 MaterializeInDestinationOp::getAliasingValues(OpOperand &opOperand,
                                               const AnalysisState &state) {
-  if (&opOperand == &getOperation()->getOpOperand(1) /*dest*/)
+  if (&opOperand == &getDestMutable()[0])
     return {{getOperation()->getResult(0), BufferRelation::Equivalent}};
   return {};
 }

mlir/lib/Dialect/Linalg/Transforms/ElementwiseOpFusion.cpp

@@ -949,7 +949,7 @@ struct FoldReshapeWithGenericOpByExpansion
           reshapeOp, "failed preconditions of fusion with producer generic op");
     }
 
-    if (!controlFoldingReshapes(&reshapeOp->getOpOperand(0))) {
+    if (!controlFoldingReshapes(&reshapeOp.getSrcMutable()[0])) {
       return rewriter.notifyMatchFailure(reshapeOp,
                                          "fusion blocked by control function");
     }

mlir/lib/Dialect/SCF/Transforms/TileUsingInterface.cpp

@@ -509,7 +509,7 @@ mlir::scf::tileAndFuseProducerOfSlice(RewriterBase &rewriter,
   // 1. Get the producer of the source (potentially walking through
   // `iter_args` of nested `scf.for`)
   auto [fusableProducer, destinationIterArg] =
-      getUntiledProducerFromSliceSource(&candidateSliceOp->getOpOperand(0),
+      getUntiledProducerFromSliceSource(&candidateSliceOp.getSourceMutable()[0],
                                         loops);
   if (!fusableProducer)
     return std::nullopt;

mlir/lib/Dialect/Tensor/Transforms/BufferizableOpInterfaceImpl.cpp

@@ -644,11 +644,11 @@ struct InsertSliceOpInterface
     RankedTensorType destType = insertSliceOp.getDestType();
 
     // The source is always read.
-    if (&opOperand == &op->getOpOperand(0) /*src*/)
+    if (&opOperand == &insertSliceOp.getSourceMutable()[0])
       return true;
 
     // For the destination, it depends...
-    assert(&opOperand == &insertSliceOp->getOpOperand(1) && "expected dest");
+    assert(&opOperand == &insertSliceOp.getDestMutable()[0] && "expected dest");
 
     // Dest is not read if it is entirely overwritten. E.g.:
     // tensor.insert_slice %a into %t[0][10][1] : ... into tensor<10xf32>
@@ -851,9 +851,8 @@ struct ReshapeOpInterface
                                                     tensor::ReshapeOp> {
   bool bufferizesToMemoryRead(Operation *op, OpOperand &opOperand,
                               const AnalysisState &state) const {
-    if (&opOperand == &op->getOpOperand(1) /* shape */)
-      return true;
-    return false;
+    auto reshapeOp = cast<tensor::ReshapeOp>(op);
+    return &opOperand == &reshapeOp.getShapeMutable()[0];
   }
 
   bool bufferizesToMemoryWrite(Operation *op, OpOperand &opOperand,
@@ -915,7 +914,8 @@ struct ParallelInsertSliceOpInterface
 
   bool bufferizesToMemoryWrite(Operation *op, OpOperand &opOperand,
                                const AnalysisState &state) const {
-    return &opOperand == &op->getOpOperand(1) /*dest*/;
+    auto parallelInsertSliceOp = cast<ParallelInsertSliceOp>(op);
+    return &opOperand == &parallelInsertSliceOp.getDestMutable()[0];
   }
 
   LogicalResult bufferize(Operation *op, RewriterBase &rewriter,

mlir/lib/IR/OperationSupport.cpp

@@ -517,6 +517,11 @@ void MutableOperandRange::updateLength(unsigned newLength) {
   }
 }
 
+OpOperand &MutableOperandRange::operator[](unsigned index) const {
+  assert(index < length && "index is out of bounds");
+  return owner->getOpOperand(start + index);
+}
+
 //===----------------------------------------------------------------------===//
 // MutableOperandRangeRange
 

mlir/lib/Transforms/Utils/CFGToSCF.cpp

@@ -277,7 +277,8 @@ class EdgeMultiplexer {
       if (index >= result->second &&
           index < result->second + edge.getSuccessor()->getNumArguments()) {
         // Original block arguments to the entry block.
-        newSuccOperands[index] = successorOperands[index - result->second];
+        newSuccOperands[index] =
+            successorOperands[index - result->second].get();
         continue;
       }