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Status – Week 272

Status – Week 272. Victor Moya. Vertex Shader. VS 2.0+ (NV30) based Vertex Shader model. Multithreaded?? Implemented with a FP array (3DLabs P10). Dynamic branching. No texture/vertx buffer load. No vertex kill. Vertex Shader. Shader Model.

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Status – Week 272

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  1. Status – Week 272 Victor Moya

  2. Vertex Shader • VS 2.0+ (NV30) based Vertex Shader model. • Multithreaded?? Implemented with a FP array (3DLabs P10). • Dynamic branching. • No texture/vertx buffer load. • No vertex kill.

  3. Vertex Shader

  4. Shader Model • Mono/Multithreaded Shader based in NV30 instruction set. • A Shader is a stream processor: • Input Stream => Input Register Bank • 16 registers in a Vertex Shader • 12 registers in Pixel Shader • Output Stream => Output Register Bank • ~16 registers in Vertex Shader • ~4 registers in Pixel Shader • Constant Memory/Register Bank • Up to 256 in Vertex Shader

  5. Shader Model • Instruction Cache/Memory • Up to 256 in Vertex Shader • 1024 in Pixel Shader • Shared between different processors (?) • Temporary and Auxiliary Registers • 16 (Vertex Shader), 32/64 (Pixel Shader) • Address Registers • Condition Code Register • Boolean Register • Loop counters • etc.

  6. Shader Model • Multithreaded: • numThreads: Number of streams that the shader can store. Includes idle and loading/unloading threads. Structures affected: Input and Output register banks. • numActiveThreads: Number of active (in execution) threads. Structures affected: temporary and auxiliary registers. PC table (in the Simulator Box). • Constant/Parameter Memory and Instruction Cache/Memory shared between all the threads. It is also shared between different Shaders (but this isn’t provided with the current model).

  7. Test Model • Three boxes: • Loader: gets commands (input stream, new programs and parameters) from a file. • Fetch: fetch instructions from a Shader program memory. • Decode/Execute: decodes and executes instructions, takes into account dependencies. • Writer: receives output stream and writes it in a file.

  8. Test Model • Wires: • Command: sends commands read from the input file to the fetch box. Latency varies for each kind of command and the data size. • New Shader Program: loads new instructions. • New Shader Parameters: loads new parameters in constant memory. • New Input: sends a new input (Vertex Input 16 4D registers). • Sync: for synchronization between Loader and Fetch (execution of a Shader Program depends from the Shader Output with the dynamic branch model). Latency 1.

  9. Test Model • Wires: • Instruction: Fetch send new instructions to Decode/Execute. Instruction EXIT marks end of Shader Program (Decode/Execute send Output to Writer). Latency 1. • NewPC: Fetch recieves control flow changes from Decode/Execute. Latency 1. • Execute: Drives execution latency for each instruction. Variable latency (1 – 5?). • Output: Decode/Execute sends the Shader Program result for the current output to the logger box (Writer). Latency constant but greater than 1 (4 or 5?).

  10. Test Model • Instruction Set: • Encoding in 128 bits. See file. • Emulation: • Separate library: ShaderEmulator.

  11. ShaderEmulator • Performs the functional emulation of the shader: • Instruction (static) management and execution. • Keeps the shader state. • Implementation: • Support for differnt MODELS?: VS1, VS2, PS1, PS2. • How to implement models? Different classess? Switch/case? • Where to keep structures related with control flow? Ex: stack, PC table.

  12. ShaderEmulator • Interface: • ShaderEmulator(numThreads, numActiveThreads, shaderModel) • LoadShaderProgram(code) • ResetShaderState(numThread) • ReadShaderState(numThread, data) • LoadShaderState(numThread, data) • ExecuteShaderInstruction(numThread, PC)

  13. ShaderInstruction • Decoded shader instruction. • What to do with shader models? Invalid instructions in different models. • Interface: • ShaderInstruction(code) • Different functions/attributes to get decoded information from the instruction (input registers, output registers, mask, swizzle, condition codes, etc.).

  14. ShaderExecInstruction • Stores a instance of an instruction that is being executed. • Carries information about the execution: • ShaderInstruction: decoded instruction. • PC: instruction memory address. • state: decode/execution/writeback/locked/… • result: result of the instruction. • startCycle: cycle in which the instruction was fetched. • Other statistics?

  15. ShaderExecInstruction • Implementation: • Avoid dynamic creation of objects. • Static pool. • Created at fetch, destroyed at decode/execute (writeback). • Can be managed by the own ShaderExecInstruction class? (static).

  16. Test Model

  17. Code Management • Directory structure: • /emu (or /emulator): functional emulation classes and functions. • /sim (or /simulator): simulation classes and functions. • /support: support functions (IO, Types, etc.).

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