Add a static assertions for custom Op<> to not defined data members (NFC)

[mehdi_amini]

Summary

A common mistake for newcomers to MLIR is to try to store extra member
on the Op class. However these are intended to be thing wrapper around
an Operation*, all the storage is meant to be encoded in attribute on
the underlying Operation. This can be confusing to debug, so better
catch it at build time.

[ftynse]

mlir/include/mlir/IR/OpDefinition.h

1792

[mehdi_amini]

Reopen, after revert because windows build was broken

[stella.stamenova]

It looks like this is causing a build failure on the windows mlir buildbot which may be the goal since the assert is firing, but it would be nice to keep the buildbot green.

https://lab.llvm.org/buildbot/#/builders/13/builds/8726

FAILED: tools/mlir/lib/IR/CMakeFiles/obj.MLIRIR.dir/BuiltinDialect.cpp.obj 
C:\PROGRA~2\MICROS~3\2017\COMMUN~1\VC\Tools\MSVC\1416~1.270\bin\Hostx64\x64\cl.exe  /nologo /TP -DBUILD_EXAMPLES -DGTEST_HAS_RTTI=0 -DMLIR_CUDA_CONVERSIONS_ENABLED=1 -DMLIR_ROCM_CONVERSIONS_ENABLED=1 -DUNICODE -D_CRT_NONSTDC_NO_DEPRECATE -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_SECURE_NO_DEPRECATE -D_CRT_SECURE_NO_WARNINGS -D_HAS_EXCEPTIONS=0 -D_SCL_SECURE_NO_DEPRECATE -D_SCL_SECURE_NO_WARNINGS -D_UNICODE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -Itools\mlir\lib\IR -IC:\buildbot\mlir-x64-windows-ninja\llvm-project\mlir\lib\IR -Iinclude -IC:\buildbot\mlir-x64-windows-ninja\llvm-project\llvm\include -IC:\buildbot\mlir-x64-windows-ninja\llvm-project\mlir\include -Itools\mlir\include /DWIN32 /D_WINDOWS   /Zc:inline /Zc:__cplusplus /Zc:strictStrings /Oi /Zc:rvalueCast /bigobj /W4 -wd4141 -wd4146 -wd4244 -wd4267 -wd4291 -wd4351 -wd4456 -wd4457 -wd4458 -wd4459 -wd4503 -wd4624 -wd4722 -wd4100 -wd4127 -wd4512 -wd4505 -wd4610 -wd4510 -wd4702 -wd4245 -wd4706 -wd4310 -wd4701 -wd4703 -wd4389 -wd4611 -wd4805 -wd4204 -wd4577 -wd4091 -wd4592 -wd4319 -wd4709 -wd4324 -w14062 -we4238 /Gw /MD /O2 /Ob2  /EHs-c- /GR- -UNDEBUG -std:c++14 /showIncludes /Fotools\mlir\lib\IR\CMakeFiles\obj.MLIRIR.dir\BuiltinDialect.cpp.obj /Fdtools\mlir\lib\IR\CMakeFiles\obj.MLIRIR.dir\ /FS -c C:\buildbot\mlir-x64-windows-ninja\llvm-project\mlir\lib\IR\BuiltinDialect.cpp
C:\buildbot\mlir-x64-windows-ninja\llvm-project\mlir\include\mlir/IR/OpDefinition.h(1783): error C2338: Op class aren't allowed to have data members
C:\buildbot\mlir-x64-windows-ninja\llvm-project\mlir\include\mlir/IR/OpDefinition.h(1782): note: while compiling class template member function 'mlir::LogicalResult mlir::Op<mlir::UnrealizedConversionCastOp,mlir::OpTrait::ZeroRegion,mlir::OpTrait::VariadicResults,mlir::OpTrait::ZeroSuccessor,mlir::OpTrait::VariadicOperands,mlir::CastOpInterface::Trait,mlir::MemoryEffectOpInterface::Trait>::verifyInvariants(mlir::Operation *)'

[stella.stamenova]

In D103869#2806893, @stella.stamenova wrote:

It looks like this is causing a build failure on the windows mlir buildbot which may be the goal since the assert is firing, but it would be nice to keep the buildbot green.

https://lab.llvm.org/buildbot/#/builders/13/builds/8726

FAILED: tools/mlir/lib/IR/CMakeFiles/obj.MLIRIR.dir/BuiltinDialect.cpp.obj 
C:\PROGRA~2\MICROS~3\2017\COMMUN~1\VC\Tools\MSVC\1416~1.270\bin\Hostx64\x64\cl.exe  /nologo /TP -DBUILD_EXAMPLES -DGTEST_HAS_RTTI=0 -DMLIR_CUDA_CONVERSIONS_ENABLED=1 -DMLIR_ROCM_CONVERSIONS_ENABLED=1 -DUNICODE -D_CRT_NONSTDC_NO_DEPRECATE -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_SECURE_NO_DEPRECATE -D_CRT_SECURE_NO_WARNINGS -D_HAS_EXCEPTIONS=0 -D_SCL_SECURE_NO_DEPRECATE -D_SCL_SECURE_NO_WARNINGS -D_UNICODE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -Itools\mlir\lib\IR -IC:\buildbot\mlir-x64-windows-ninja\llvm-project\mlir\lib\IR -Iinclude -IC:\buildbot\mlir-x64-windows-ninja\llvm-project\llvm\include -IC:\buildbot\mlir-x64-windows-ninja\llvm-project\mlir\include -Itools\mlir\include /DWIN32 /D_WINDOWS   /Zc:inline /Zc:__cplusplus /Zc:strictStrings /Oi /Zc:rvalueCast /bigobj /W4 -wd4141 -wd4146 -wd4244 -wd4267 -wd4291 -wd4351 -wd4456 -wd4457 -wd4458 -wd4459 -wd4503 -wd4624 -wd4722 -wd4100 -wd4127 -wd4512 -wd4505 -wd4610 -wd4510 -wd4702 -wd4245 -wd4706 -wd4310 -wd4701 -wd4703 -wd4389 -wd4611 -wd4805 -wd4204 -wd4577 -wd4091 -wd4592 -wd4319 -wd4709 -wd4324 -w14062 -we4238 /Gw /MD /O2 /Ob2  /EHs-c- /GR- -UNDEBUG -std:c++14 /showIncludes /Fotools\mlir\lib\IR\CMakeFiles\obj.MLIRIR.dir\BuiltinDialect.cpp.obj /Fdtools\mlir\lib\IR\CMakeFiles\obj.MLIRIR.dir\ /FS -c C:\buildbot\mlir-x64-windows-ninja\llvm-project\mlir\lib\IR\BuiltinDialect.cpp
C:\buildbot\mlir-x64-windows-ninja\llvm-project\mlir\include\mlir/IR/OpDefinition.h(1783): error C2338: Op class aren't allowed to have data members
C:\buildbot\mlir-x64-windows-ninja\llvm-project\mlir\include\mlir/IR/OpDefinition.h(1782): note: while compiling class template member function 'mlir::LogicalResult mlir::Op<mlir::UnrealizedConversionCastOp,mlir::OpTrait::ZeroRegion,mlir::OpTrait::VariadicResults,mlir::OpTrait::ZeroSuccessor,mlir::OpTrait::VariadicOperands,mlir::CastOpInterface::Trait,mlir::MemoryEffectOpInterface::Trait>::verifyInvariants(mlir::Operation *)'

Looks like you already caught it. Thanks!

[mehdi_amini]

Fix MSVC

[mehdi_amini]

@stella.stamenova relanded in 1b21e9c1fa99, the premerge passed on Windows here, but feel free to revert if you see any failure!

mlir/include/mlir/IR/OpDefinition.h

private:
   }
   static void printAssembly(Operation *op, OpAsmPrinter &p) {
     return cast<ConcreteType>(op).print(p);
   }
   /// Implementation of `VerifyInvariantsFn` AbstractOperation hook.
   static AbstractOperation::VerifyInvariantsFn getVerifyInvariantsFn() {
     return &verifyInvariants;
   }
+
+  static constexpr bool hasNoDataMembers() {
+    // Checking that the derived class does not define any member by comparing
+    // its size to an ad-hoc EmptyOp.
+    class EmptyOp : public Op<EmptyOp, Traits...> {};
+    return sizeof(ConcreteType) == sizeof(EmptyOp);
+  }
+
   static LogicalResult verifyInvariants(Operation *op) {
+    static_assert(hasNoDataMembers(),
+                  "Op class shouldn't define new data members");
     return failure(
         failed(op_definition_impl::verifyTraits<VerifiableTraitsTupleT>(op)) ||
         failed(cast<ConcreteType>(op).verify()));
   }
 
   /// Allow access to internal implementation methods.
   friend AbstractOperation;
 };