[mlir][docgen] Only emit class name

[jpienaar]

Summary

The fully qualified name gets long in the TOC (especially on mobile).

[scotttodd]

mlir/tools/mlir-tblgen/OpDocGen.cpp

168–170

Are there command line flags or options that can apply to op doc generation? I wonder if anyone would want to choose between these two behaviors. For example, the upstream dialects can have pretty short fully qualified names like ::mlir::math::FloorOp, while in projects like IREE we have longer names like ::mlir::iree_compiler::IREE::Stream::ExecutableOp.

[jpienaar]

Make it optional and set to false initial to be NOP.

[jpienaar]

Flip to enabling specifying a prefix to strip, makes it so that projects could strip a common prefix rather than all or nothing. I think this is most useful for where folks are working in a given namespace. I could also make it an option to just use class name, but this does enable it still just manually.

[scotttodd]

In D152404#4405945, @jpienaar wrote:

Flip to enabling specifying a prefix to strip, makes it so that projects could strip a common prefix rather than all or nothing. I think this is most useful for where folks are working in a given namespace. I could also make it an option to just use class name, but this does enable it still just manually.

SGTM. I think this will work well enough in IREE, since we have a tablegen_doc build system function (e.g. https://github.com/openxla/iree/blob/main/build_tools/cmake/iree_tablegen_doc.cmake) that we call for each dialect. We can add flags to each, or add a default that would apply across the project.

mlir/tools/mlir-tblgen/OpDocGen.cpp

 #include "OpGenHelpers.h"
 #include "mlir/Support/IndentedOstream.h"
 #include "mlir/TableGen/AttrOrTypeDef.h"
 #include "mlir/TableGen/GenInfo.h"
 #include "mlir/TableGen/Operator.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/Regex.h"
 #include "llvm/Support/Signals.h"
 #include "llvm/TableGen/Error.h"
 #include "llvm/TableGen/Record.h"
 #include "llvm/TableGen/TableGenBackend.h"
 
 #include <set>
+#include <string>
+
+//===----------------------------------------------------------------------===//
+// Commandline Options
+//===----------------------------------------------------------------------===//
+static llvm::cl::OptionCategory docCat("Options for -gen-(attrdef|typedef|op|dialect)-doc");
+llvm::cl::opt<std::string> stripPrefix(
+    "strip-prefix",
+    llvm::cl::desc("Strip prefix of the fully qualified names"),
+    llvm::cl::init("::mlir::"), llvm::cl::cat(docCat));
 
 using namespace llvm;
 using namespace mlir;
 using namespace mlir::tblgen;
-
 using mlir::tblgen::Operator;
 
 // Emit the description by aligning the text to the left per line (e.g.,
 // removing the minimum indentation across the block).
 //
 // This expects that the description in the tablegen file is already formatted
 // in a way the user wanted but has some additional indenting due to being
 // nested in the op definition.
static void emitOpTraitsDoc(const Operator &op, raw_ostream &os) {
   }
   if (!effects.empty()) {
     llvm::interleaveComma(effects, os << "\nEffects: ");
     os << "\n";
   }
 }
 
 static void emitOpDoc(const Operator &op, raw_ostream &os) {
-  os << llvm::formatv("### `{0}` ({1})\n", op.getOperationName(),
-                      op.getQualCppClassName());
+  std::string classNameStr = op.getQualCppClassName();
+  StringRef className = classNameStr;
+  (void)className.consume_front(stripPrefix);
+  os << llvm::formatv("### `{0}` ({1})\n", op.getOperationName(), className);
 
   // Emit the summary, syntax, and description if present.
   if (op.hasSummary())
     os << "\n**Summary:** _" << op.getSummary() << "_\n\n";
   if (op.hasAssemblyFormat())
     emitAssemblyFormat(op.getOperationName(), op.getAssemblyFormat().trim(),
                        os);
   if (op.hasDescription())