Cheng Shao authored May 30, 2024 and Marge Bot committed Jun 04, 2024

We have formally dropped i386 windows support (#18487) a long time
ago. The stdcall foreign call convention is only used by i386 windows,
and the legacy logic around it is a significant maintenance burden for
future work that adds arm64 windows support (#24603). Therefore, this
patch removes stdcall support completely from the compiler as well as
the RTS (#24883):

- stdcall is still recognized as a FFI calling convention in Haskell
  syntax. GHC will now unconditionally emit a warning
  (-Wunsupported-calling-conventions) and treat it as ccall.
- Apart from minimum logic to support the parsing and warning logic,
  all other code paths related to stdcall has been completely stripped
  from the compiler.
- ghci only supports FFI_DEFAULT_ABI and ccall convention from now on.
- FFI foreign export adjustor code on all platforms no longer handles
  the stdcall case and only handles ccall from now on.
- The Win32 specific parts of RTS no longer has special co...