I don't think that's such a great example in this context.
Qualcomm, Mediatek, etc. are hardware vendors after all. Software to them is a necessary evil, not a reason d'être or complementary tool (as it is for NVIDIA and Intel). Their customers fall in the same category - smartphone manufacturers want to sell units, not keep software up-to-date.
https://www.msn.com/en-us/money/technologyinvesting/nvidia-i...
It's a very similar story for Intel. NVIDIA and Intel are selling hardware because of their software portfolio. How many GPUs would NVIDIA sell in the HPC market if it wasn't for CUDA and the various support libraries around it?
Intel's non-client solution revenue was over 40% of their total revenue in 2020. This includes their (software-) AI solutions, applications, licence business and services. So Intel, too makes a significant amount of money from software and services around their software ecosystem.
We don't have to hypothesize about this. The HPC GPU market has multiple vendors, just look at how many HPC GPUs AMD or Intel are selling: AMD and Intel have ~0.8% or so market share. NVIDIA has >99%.
Pretty much every review of HPC GPUs states that AMD GPUs are both faster and cheaper.
So how come they don't sell?
The answer is software.
That said, this "junk" dump can still be used by the community of users to upgrade themselves the software on that hardware, so that's still a nice improvement.
Back to LLVM the question is whether these companies decide to not contribute upstream because they don't bother to make clean patches or because they want to keep it for themselves.
I'd argue that they would be much better off long-term making clean patches anyway, so that's not a valid reason for not contributing.
And even if theynjust dumped their patches, the community could still take them and incorporate nice optimization into upstream.
Android is a great example. Typical Qualcomm/Mediatek/etc. behavior: take a "stable" kernel, stuff it with custom undocumented drivers and junk, be stuck on that version forever. The only thing the GPL changes is the vendor posts a source dump of dubious usefulness in some obscure section of their website.