Programmable Graphics Shader Loop and Branch Instruction Processing
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Solution Overview
Problem
Current graphics processors lack support for loop and branch instructions, leading to inefficient shader programs that require more storage and bandwidth due to the need for explicit instructions for each iteration, resulting in longer programs and increased memory usage.
Innovation Solution
A programmable shader system that includes an instruction processing unit capable of converting shader program instructions into a sequence of codewords, allowing for the execution of loop and branch instructions, thereby reducing the number of lines of code and memory required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If loop and branch instructions are not supported in shader programs, then the graphics processor has simpler instruction execution, but the shader programs become longer and require more memory storage and bandwidth
Solution Approach 1:
An instruction processing unit is introduced as an intermediary component between the shader program storage and the execution units. This unit automatically generates and manages the sequence of codewords needed to implement loop and branch instructions, shielding the execution units from the complexity of loop control while enabling compact shader programs with loop constructs.
2Device complexity
If loop instructions are not supported, then the instruction processing unit has simpler functionality, but more memory bandwidth is required to download shader programs
Solution Approach 1:
The loop control logic is extracted from the main shader execution path and implemented as a separate instruction processing unit. This unit handles loop counter management and branch decision-making independently, allowing the core shader execution units to focus on computation while the instruction processing unit manages control flow, thereby reducing the overall shader program size and memory bandwidth requirements.
3Ease of operation
If shader programs explicitly include all loop iterations, then execution is straightforward, but the number of program instructions increases significantly
Solution Approach 1:
The instruction processing unit implements self-service by automatically generating the sequence of codewords needed to execute loop bodies. When a loop instruction is encountered in the shader program, the instruction processing unit autonomously creates the necessary control structures and repeats the loop body execution according to the specified iteration count, eliminating the need for manual unrolling of loop iterations in the shader program.
Data Source
AI summary
A method and apparatus for executing loop and branch program instructions in a programmable graphics shader. The programmable graphics shader converts a sequence of instructions comprising a portion of a shader program and selects a first set of fragments to be processed. Subsequent sequences of instructions are converted until all of the instructions comprising the shader program have been executed on the first set of fragments. Each remaining set of fragments is processed by the shader program until all of the fragments are processed in the same manner. Furthermore, the instructions can contain one or more loop or branch program instructions that are conditionally executed. Additionally, when instructions within a loop as defined by a loop instruction are being executed a current loop count is pipelined through the programmable graphics shader and used as an index to access graphics memory.