How to Debug swiftshader process pipeline

[Jack Scho]

As we known Reactor produce code for JIT, 

but if i wanna debug some rendering process, it seems hard to get the actual value for the variable.

For example, if i wanna to know the value for area in SetupRoutine, gdb shows "rr::LValue<Float>" , not the value of A.

it`s just i want to know how swiftshader render triangles into screen.

and how you guys debug and develop swiftshader process, just write the reactor code and run it?

[Jack Scho]

https://github.com/google/swiftshader/blob/master/docs/ReactorDebugInfo.md

As this md says using  REACTOR_EMIT_DEBUG_INFO when build swiftshader,

but not achieve the goal of show the actual value for area A

[Jack Scho]

i found rr::Print() can print the actual value of area A

is there any other methods?

[Jack Scho]

means any other methods for tracing the value of A like gdb step by step show .

[Nicolas Capens]

Hi Jack,

Thanks for your interest in SwiftShader! Indeed when the Reactor statements execute, they just record which operations to JIT-compile into binary code. Debugging the execution of the generated code is mostly limited to inserting rr::Print() calls, using rr::Call() to call a C function to which you can pass values and where you can put a breakpoint, or writing values to a buffer that can be inspected using a C++ debugger.

The REACTOR_EMIT_DEBUG_INFO option requires a very specific setup and has probably bitrotted quite a bit. Hopefully once we have full C++23 support we could base it around std::stacktrace and make it work universally, but that's a way off.

I recommend trying out the rr::Call() approach. Unlike the use of rr::Print() you can easily use breakpoints and limit it to specific conditions.

Cheers,

Nicolas

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[Jack Scho]

Thanks for your kind reply, I will try rr::Call.

[PP hhhzz]

Hi,

If I want to print the values of a struct, how should I use the rr::Print() function?

Best regards, 

Haozhou

[Nicolas Capens]

Hi Haozhou,

You can either use rr::Print() to print each struct element individually (or just the ones of interest), or use rr::Call() to pass a pointer to the struct instance to a custom C function where you do the printing. Because you can also put breakpoints in the latter, and easily add conditions for when to print/break, I'd recommend the latter approach over using rr::Print().

Cheers,

Nicolas

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