GfxRuntime140 convention

GfxRuntime140 is a legacy AOT module convention that serves the Vulkan, Metal and OpenGL backends.

GfxRuntime140 only accepts SPIR-V as the only valid code artifact. For each SPIR-V artifact, all of the following requirements must be satisfied.

• SPIR-V module version is 1.3 or higher.
• There is only one entry point function called main. It's execution model is GLCompute. Workgroup size Y and Z are always 1.
• There is only one descriptor set, where Set=0.
• The context buffer is a uniform bufffer in std140 layout, bound to Binding=0. Its elements are aligned to 4 bytes. The size is at least 1536 bytes. The context buffer content must be consumed following the rules listed below in "Context buffer format".
• The root buffer is a storage buffer in std430 layout, bound to Binding=1.
• ND-arrays are storage buffers in std430 layout, bound to Binding>=2 in argument order.

Context buffer layout

The context buffer has the following constituents sequentially in order:

• Argument values. Size of this section depends on the number of arguments and the types of the arguments.
  • 8-bit scalars take 4 bytes. Valid value in 1 byte from lower address.
  • 16-bit scalars take 4 bytes. Valid value in 2 bytes from lower address.
  • 32-bit scalars take 4 bytes.
  • 64-bit scalars take 8 bytes.
  • N-D arrays and textures take 4 bytes. Never use the values.
• Extra arguments for N-D arrays and textures in the first 32 arguments, 12 extra arguments for each. Exactly take 32 * 12 * 4 = 1536 bytes
  • Scalars zeros all its 12 extra argumnts.
  • N-D arrays stores its shape in the extra arguments. If a N-D array uses less than 12 dimensions, the trailing extra arguments are zeroed.
  • Textures stores its width, height and depth in the extra arguments. The trailing dimensions are zeroed.