Hi everyone. We’re exploring the possibility of dropping 387 floating-point support and requiring SSE2 support for GOARCH=386 in the native gc compiler, potentially in Go 1.16. This would raise the minimum GOARCH=386 requirement to the Intel Pentium 4 (released in 2000) or AMD Opteron/Athlon 64 (released in 2003).
There are several reasons we’re considering this:
- While 387 support isn’t a huge maintenance burden, it does take time away from performance and feature work and represents a fair amount of latent complexity.
- 387 support has been a regular source of bugs (#36400, #27516, #22429, #17357, #13923, #12970, #4798, just to name a few).
- 387 bugs often go undetected for a long time because we don’t have builders that support only 387 (so unsupported instructions can slip in unnoticed).
- Raising the minimum requirement to SSE2 would allow us to also assume many other useful architectural features, such as proper memory fences and 128 bit registers, which would simplify the compiler and runtime and allow for much more efficient implementations of core functions like memmove on 386.
- We’re exploring switching to a register-based calling convention in Go 1.16, which promises significant performance improvements, but retaining 387 support will definitely complicate this and slow our progress.
The gccgo toolchain will continue to support 387 floating-point, so this remains an option for projects that absolutely must use 387 floating-point.
We’d like to know if there are still significant uses of GO386=387, particularly for which using gccgo would not be a viable option.