I’ve just released a small one C++ file tool called spirv-stats. It will take one or more SPIR-V input files, and calculate the composition of the SPIR-V shader modules like so:

It firstly outputs the total number of hits in the SPIR-V shader module(s) - this is the total number of opcodes found within the module(s). Then it outputs the total byte size of the module(s), followed by a sorted breakdown of the module(s), with the most hit opcodes coming first.

I decided to run this across the various folders of SPIR-V that @aras_p is using in his smol-v tool, with the following results.

dota2⌗

OpMemberDecorate dominates the dota2 shaders - nearly 20% of the module is decorating members of structs! Next we have OpLoad at 16% of the hits, but with 13% of the size of the files, followed by OpAccessChain at 10% of the hits and 12% of the size. Most of the shader module(s) are taken up with decorating struct members, and then loading and storing to various variables.

shadertoy⌗

The shadertoy folder is dominated by loads and stores. Then curiously OpLabel - this indicates that there is a heavy amount of branching/looping occurring in the source shaders, as an OpLabel signifies a new basic block has been declared. OpBranch is the sixth most used opcode, which also backs up the view that these shaders make heavy use of branching/looping.

talos⌗

The talos folder is dominated once again by loads and stores. Next is OpCompositeExtract - which is extracting an element from a composite (aggregate, matrix or vector). I’d take a guess that there is a lot of vector math going on in these shaders, as the sixth most used opcode is OpVectorShuffle.

unity⌗

And lastly the unity folder. These shader modules are dominated by OpDecorate. The next three most used opcodes are OpLoad, OpStore and OpAccessChain - so loading and storing to variables is taking up a sizeable amount of the shader modules.

All Together⌗

If we look at all the folders above as one output from  spirv-stats instead:

We can see that loading and storing dominates our shader modules at 28% of the opcodes and 25% of the binary size.

Summary⌗

The tool showed us some interesting divergent trends across each of the providers of the SPIR-V shader modules. Thanks to Valve, Shadertoy, Croteam and Unity for allowing @aras_p to use their SPIR-V shaders when he wrote his smol-v tool. I wouldn’t have had such interesting source material otherwise to run my tool against!

The  spirv-stats tool can be got via its GitHub repository - hope it is useful to someone!