SPIR-V doesn't support parallelisation in patch constant functions. Merging into one phase allows generation of a single patch constant function and normalises to the shader model 6 pattern.
-- v4: vkd3d-shader/spirv: Merge all shader IR fork and join phases into a single phase. vkd3d-shader/spirv: Pass a parser pointer to spirv_compiler_generate_spirv(). vkd3d-shader/sm4: Use the instruction array interface in compile_dxbc_tpf(). vkd3d-shader/glsl: Use the instruction array interface in vkd3d_glsl_generator_generate(). vkd3d-shader: Use the instruction array interface in scan_with_parser(). vkd3d-shader/trace: Use the instruction array interface in vkd3d_dxbc_binary_to_text(). vkd3d-shader: Initialise the instruction array in vkd3d_shader_parser_init(). vkd3d-shader/sm4: Store parsed instructions in an array. vkd3d-shader/sm1: Store parsed instructions in an array.