[mlir][ODS] Add OptionalTypesMatchWith and remove a custom assemblyFormat (#68876)

This is just a slight specialization of `TypesMatchWith` that returns
success if an optional parameter is missing.

There may be other places this could help e.g.:

https://github.com/llvm/llvm-project/blob/eb21049b4b904b072679ece60e73c6b0dc0d1ebf/mlir/include/mlir/Dialect/X86Vector/X86Vector.td#L58-L59
...but I'm leaving those to avoid some churn.

This constraint will be handy for us in some later patches, it's a
formalization of a short circuiting trick with the `comparator` of the
`TypesMatchWith` constraint (devised for #69195).

```
TypesMatchWith<
  "padding type matches element type of result (if present)",
  "result", "padding",
  "::llvm::cast<VectorType>($_self).getElementType()",
  // This returns true if no padding is present, or it's present with a type that matches the element type of `result`.
  "!getPadding() || std::equal_to<>()">
```

This is a little non-obvious, so after this patch you can instead do:
```
OptionalTypesMatchWith<
  "padding type matches element type of result (if present)",
  "result", "padding",
  "::llvm::cast<VectorType>($_self).getElementType()">
```

Author: MacDue

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

@@ -215,6 +215,8 @@ def Vector_ReductionOp :
   Vector_Op<"reduction", [Pure,
      PredOpTrait<"source operand and result have same element type",
                  TCresVTEtIsSameAsOpBase<0, 0>>,
+     OptionalTypesMatchWith<"dest and acc have the same type",
+                            "dest", "acc", "::llvm::cast<Type>($_self)">,
      DeclareOpInterfaceMethods<ArithFastMathInterface>,
      DeclareOpInterfaceMethods<MaskableOpInterface>,
      DeclareOpInterfaceMethods<VectorUnrollOpInterface, ["getShapeForUnroll"]>
@@ -263,9 +265,8 @@ def Vector_ReductionOp :
                          "::mlir::arith::FastMathFlags::none">:$fastMathFlags)>
   ];
 
-  // TODO: Migrate to assemblyFormat once `AllTypesMatch` supports optional
-  // operands.
-  let hasCustomAssemblyFormat = 1;
+  let assemblyFormat = "$kind `,` $vector (`,` $acc^)? (`fastmath` `` $fastmath^)?"
+                       " attr-dict `:` type($vector) `into` type($dest)";
   let hasCanonicalizer = 1;
   let hasVerifier = 1;
 }

mlir/include/mlir/IR/OpBase.td

@@ -568,6 +568,14 @@ class TypesMatchWith<string summary, string lhsArg, string rhsArg,
   string transformer = transform;
 }
 
+// The same as TypesMatchWith but if either `lhsArg` or `rhsArg` are optional
+// and not present returns success.
+class OptionalTypesMatchWith<string summary, string lhsArg, string rhsArg,
+                     string transform, string comparator = "std::equal_to<>()">
+  : TypesMatchWith<summary, lhsArg, rhsArg, transform,
+     "!get" # snakeCaseToCamelCase<lhsArg>.ret # "()"
+     # " || !get" # snakeCaseToCamelCase<rhsArg>.ret # "() || " # comparator>;
+
 // Special variant of `TypesMatchWith` that provides a comparator suitable for
 // ranged arguments.
 class RangedTypesMatchWith<string summary, string lhsArg, string rhsArg,

mlir/include/mlir/IR/Utils.td

@@ -66,4 +66,28 @@ class CArg<string ty, string value = ""> {
   string defaultValue = value;
 }
 
+// Helper which makes the first letter of a string uppercase.
+// e.g. cat -> Cat
+class firstCharToUpper<string str>
+{
+  string ret = !if(!gt(!size(str), 0),
+    !toupper(!substr(str, 0, 1)) # !substr(str, 1),
+    "");
+}
+
+class _snakeCaseHelper<string str> {
+  int idx = !find(str, "_");
+  string ret = !if(!ge(idx, 0),
+    !substr(str, 0, idx) # firstCharToUpper<!substr(str, !add(idx, 1))>.ret,
+    str);
+}
+
+// Converts a snake_case string to CamelCase.
+// TODO: Replace with a !tocamelcase bang operator.
+class snakeCaseToCamelCase<string str>
+{
+  string ret = !foldl(firstCharToUpper<str>.ret,
+    !range(0, !size(str)), acc, idx, _snakeCaseHelper<acc>.ret);
+}
+
 #endif // UTILS_TD

mlir/lib/Dialect/Vector/IR/VectorOps.cpp

@@ -524,47 +524,6 @@ LogicalResult ReductionOp::verify() {
   return success();
 }
 
-ParseResult ReductionOp::parse(OpAsmParser &parser, OperationState &result) {
-  SmallVector<OpAsmParser::UnresolvedOperand, 2> operandsInfo;
-  Type redType;
-  Type resType;
-  CombiningKindAttr kindAttr;
-  arith::FastMathFlagsAttr fastMathAttr;
-  if (parser.parseCustomAttributeWithFallback(kindAttr, Type{}, "kind",
-                                              result.attributes) ||
-      parser.parseComma() || parser.parseOperandList(operandsInfo) ||
-      (succeeded(parser.parseOptionalKeyword("fastmath")) &&
-       parser.parseCustomAttributeWithFallback(fastMathAttr, Type{}, "fastmath",
-                                               result.attributes)) ||
-      parser.parseColonType(redType) ||
-      parser.parseKeywordType("into", resType) ||
-      (!operandsInfo.empty() &&
-       parser.resolveOperand(operandsInfo[0], redType, result.operands)) ||
-      (operandsInfo.size() > 1 &&
-       parser.resolveOperand(operandsInfo[1], resType, result.operands)) ||
-      parser.addTypeToList(resType, result.types))
-    return failure();
-  if (operandsInfo.empty() || operandsInfo.size() > 2)
-    return parser.emitError(parser.getNameLoc(),
-                            "unsupported number of operands");
-  return success();
-}
-
-void ReductionOp::print(OpAsmPrinter &p) {
-  p << " ";
-  getKindAttr().print(p);
-  p << ", " << getVector();
-  if (getAcc())
-    p << ", " << getAcc();
-
-  if (getFastmathAttr() &&
-      getFastmathAttr().getValue() != arith::FastMathFlags::none) {
-    p << ' ' << getFastmathAttrName().getValue();
-    p.printStrippedAttrOrType(getFastmathAttr());
-  }
-  p << " : " << getVector().getType() << " into " << getDest().getType();
-}
-
 // MaskableOpInterface methods.
 
 /// Returns the mask type expected by this operation.

mlir/test/Dialect/Vector/invalid.mlir

@@ -1169,7 +1169,7 @@ func.func @reduce_unsupported_attr(%arg0: vector<16xf32>) -> i32 {
 // -----
 
 func.func @reduce_unsupported_third_argument(%arg0: vector<16xf32>, %arg1: f32) -> f32 {
-  // expected-error@+1 {{'vector.reduction' unsupported number of operands}}
+  // expected-error@+1 {{expected ':'}}
   %0 = vector.reduction <add>, %arg0, %arg1, %arg1 : vector<16xf32> into f32
 }
 

mlir/test/mlir-tblgen/utils.td

@@ -0,0 +1,23 @@
+// RUN: mlir-tblgen -I %S/../../include %s | FileCheck %s
+
+include "mlir/IR/Utils.td"
+
+// CHECK-DAG: string value = "CamelCaseTest"
+class already_camel_case {
+  string value = snakeCaseToCamelCase<"CamelCaseTest">.ret;
+}
+
+// CHECK-DAG: string value = "Foo"
+class single_word {
+  string value = snakeCaseToCamelCase<"foo">.ret;
+}
+
+// CHECK-DAG: string value = "ThisIsATest"
+class snake_case {
+  string value = snakeCaseToCamelCase<"this_is_a_test">.ret;
+}
+
+// CHECK-DAG: string value = "ThisIsATestAgain"
+class extra_underscores {
+  string value = snakeCaseToCamelCase<"__this__is_a_test__again__">.ret;
+}