[Misc] Add TAICHI_DUMP_IR and TAICHI_LOAD_IR

[hughperkins]

Issue: #

Brief Summary

Add TAICHI_DUMP_IR and TAICHI_LOAD_IR

Allows you to dump IR from various stages in the pipeline, by defining TAICHI_DUMP_IR (eg to '1').

• the IR will be dumped to files in /tmp/ir folder

You can also load from the IR using TAICHI_LOAD_IR

• this will load from the same folder
• in the case of CUDA, it will load the IR just before we drop into PTX

copilot:summary

Walkthrough

copilot:walkthrough

[hughperkins]

Lets close this for now. Will reopen once number of PRs drops a bit :)

[hughperkins]

Maybe I'll just go ahead and open all PRs

[bo-rc]

Prefer to use RAII (scoped initialization in modern C++) here:

const std::string filename = dumpOutDir / (kernel_name + ".spirv");

// 'out_file' automatically closed after the code block
if (std::ofstream out_file(filename); out_file) {
    out_file.write(spirv_asm.data(), spirv_asm.size());
} else {
    // Handle the error
}

[duburcqa]

This pattern is a bit confusing and not so common but why not.

[bo-rc]

Scoped initialization is introduced in C++17 and beyond. A much safer approach (resource creation, initialization, destruction within a given scope, out_file cannot be accidentally used out of the code scope) that also expresses the intent (out_file is only used within this given local scope / code block).

[bo-rc]

nested if can be flatten

[bo-rc]

It might be just style preferences. It depends on the style guidelines of this repo. The comments may apply to multiple repetitive sections.

[bo-rc]

Style refactor may come later.