Include GPU source kernels in Stmt and StmtHtml file.

[mcourteaux]

This works for me nicely with CUDA, OpenCL, OpenGLCompute, Direct3D12Compute, and Metal as backends. I tried collapsing the code for all of them and it works nicely. I put everything in a <pre> for the HTML output. Not sure if any of the backends produce non-compatible characters that might break the HTML, but for my kernels, it didn't.

[mcourteaux]

This mostly fixes #6410.

[abadams]

Thanks! To me this seems like a reasonably elegant solution. It might be better if we tracked embedded data buffers and embedded kernel source buffers in separate vectors in the Module class so that we didn't print based on a suffix of the name, but I'm happy with the PR as-is if you don't want to do that.

Also looks like it needs a clang-format run.

[mcourteaux]

I don't think it's easy to do, as the Buffers get added to the Module here:

Halide/src/Lower.cpp

Lines 467 to 471 in 8b68f85

	if (arg.buffer.defined() && !found) {
	// It's a raw Buffer used that isn't in the args
	// list. Embed it in the output instead.
	debug(1) << "Embedding image " << arg.buffer.name() << "\n";
	result_module.append(arg.buffer);

And the only thing we have left is the fact that it's a Buffer, and not what it's used for, as far as I can tell at least.

For the clang-format, I ran clang-format, and force pushed. Not sure if that's the way things go here (wrt to the CI), but I'd liked to see one commit for this instead of two 😋

[abadams]

Oh right, OffloadGPULoops just adds a reference to it and assumes it'll get picked up. I guess it would have to be a flag on the buffer, which would be a little gross.

Probably inject_gpu_offload should take the module and add the kernel source buffers to it directly, but then you'd have to make sure they don't redundantly get added again...

Let's not deal with it in this PR.

[abadams]

Oh, and for clang-format we normally push a second commit rather than force-pushing, and then squash the commits into one when we merge.