Fix matmul's indexing_maps issue

Author: rolfmorel

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

@@ -555,6 +555,22 @@ def BroadcastOp : LinalgStructuredBase_Op<"broadcast", [
 // Op definition for MatmulOp
 //===----------------------------------------------------------------------===//
 
+
+// DONOTMERGE(rolfmorel): explain why the below is necessary
+def DefaultValuedMatmulIndexingMapsAttr :
+    Attr<AffineMapArrayAttr.predicate, AffineMapArrayAttr.summary> {
+  let storageType = AffineMapArrayAttr.storageType;
+  let returnType = AffineMapArrayAttr.returnType;
+  let convertFromStorage = AffineMapArrayAttr.convertFromStorage;
+  let constBuilderCall = "$_builder.getAffineMapArrayAttr($0.empty() ? MatmulOp::getDefaultIndexingMaps($_builder.getContext()) : $0)";
+  let defaultValue = "SmallVector<AffineMap>()";
+  let valueType = AffineMapArrayAttr.valueType;
+  let isOptional = 1;
+
+  let baseAttr = AffineMapArrayAttr;
+}
+
+
 def MatmulOp : LinalgStructuredBase_Op<"matmul", [
                AttrSizedOperandSegments,
                LinalgContractionOpInterface]> {
@@ -606,7 +622,7 @@ def MatmulOp : LinalgStructuredBase_Op<"matmul", [
     let arguments = (ins
       Variadic<AnyType>:$inputs,
       Variadic<AnyShaped>:$outputs,
-      DefaultValuedOptionalAttr<AffineMapArrayAttr, "{}">:$indexing_maps,
+      DefaultValuedMatmulIndexingMapsAttr:$indexing_maps, // DONOTMERGE(rolfmorel): explain why this is necessary
       DefaultValuedOptionalAttr<TypeFnAttr, "TypeFn::cast_signed">:$cast
     );
     let results = (outs Variadic<AnyRankedTensor>:$result_tensors);

mlir/python/mlir/dialects/linalg/__init__.py

@@ -149,6 +149,11 @@ def __init__(
 generic = region_op(GenericOp_, terminator=YieldOp)
 
 
+@register_attribute_builder("DefaultValuedMatmulIndexingMapsAttr")
+def _DefaultValuedMatmulIndexingMapsAttr(x, context):
+    return ArrayAttr.get([AffineMapAttr.get(v) for v in x])
+
+
 def matmul(
     inputs: Sequence[Union[Operation, OpView, Value]],
     *,

mlir/test/python/dialects/linalg/ops.py

@@ -337,9 +337,7 @@ def matmul_op(A, Amem, B, Bmem, Btransposed, Btransposedmem, C, Cmem):
                 )
                 linalg.fill_builtin_region(res.operation)
                 # CHECK: linalg.matmul ins(%[[Amem]], %[[Bmem]] : memref<4x8xf32>, memref<8x12xf32>) outs(%[[Cmem]] : memref<4x12xf32>)
-                linalg.matmul(
-                    (Amem, Bmem), outs=(Cmem,)
-                )
+                linalg.matmul((Amem, Bmem), outs=(Cmem,))
 
                 # CHECK: linalg.matmul indexing_maps = [#[[$A_MAP]], #[[$BTrans_MAP]], #[[$C_MAP]]] ins(%[[Amem]], %[[BTransmem]] : memref<4x8xf32>, memref<12x8xf32>) outs(%[[Cmem]] : memref<4x12xf32>)
                 res = linalg.MatmulOp(