CMake: Add support for pasm2asm on NASM source files

[dnakamura]

Signed-off-by: Devin Nakamura devinn@ca.ibm.com

[charliegracie]

Why do we need to run a preprocess on the nasm files? Can you provide an example? NASM should have enough support that a preprocessor seems redundant and cumbersome for no reason.

[dnakamura]

.pnasm files do exist in OpenJ9. (https://github.com/eclipse/openj9/blob/master/runtime/compiler/x/runtime/X86PicBuilder.pnasm)

It looks like its just so that it can consume j9cfg.h

[charliegracie]

As far as I can tell j9cfg.h from the OpenJ9 project is a generated file.... wouldn't it make more sense to generate a NASM consumable version of j9cfg.h (j9cfgh.inc?) and include that properly in NASM instead of preprocessing all of the NASM files?

[0xdaryl]

I believe there is only one #define that's needed from j9cfg.h. @nbhuiyan planned on modifying the jilconsts generator to add the needed definition in there to avoid this dependency. That work is planned for by end of October. The initial version, however, still relies on the C preprocessor unfortunately.

[charliegracie]

From a quick look at jilconsts.h and jilconsts.c it would be a smaller change to add this one define to be written out in writeConstants than it would be to make this change. This change is small but adding 3 lines to jilconsts.c would be just as easy and would happen in the project that requires the code and not pus work down onto OMR which technically does not belong in this project.

I could be missing something about jilconsts?

[charliegracie]

I would personally prefer to see new work for a downstream project happen in the downstream project and not in OMR whenever possible. If it is a matter of adding 1 new constant to jilconsts would that actually be easier / simpler than making a change in OMR and forcing cpp to be run on the files?

[0xdaryl]

@nbhuiyan : you've studied that code more than I have. Is the change that straightforward? If so, please make it in OpenJ9 so we can avoid this OMR dependence.

[nbhuiyan]

@0xdaryl Yes, the change is pretty straightforward. I was already planning on not making use of the C Preprocessor right when I was preparing the initial version of the NASM files. However, I decided to delay that as there were suddenly some activity over the last month in the MASM-equivalent .pasm files, and resulted in even more reliance on the C Preprocessor in X86PicBuilder.

I think we can get rid of the .pnasm files easily through writing the constant out into jilconsts.inc. I agree with @charliegracie and think we should not have to make a change in OMR for something like this.

[nbhuiyan]

@0xdaryl @charliegracie @dnakamura eclipse-openj9/openj9#3243 would remove the need for the C preprocessor for NASM files.

[0xdaryl]

Thanks. This PR should be closed then.

[charliegracie]

Closing as per the comment from @nbhuiyan