function-return
The tracking issue for this feature is: https://github.com/rust-lang/rust/issues/116853.
Option -Zfunction-return controls how function returns are converted.
It is equivalent to Clang's and GCC's -mfunction-return. The Linux kernel
uses it for RETHUNK builds. For details, see LLVM commit 2240d72f15f3 ("[X86]
initial -mfunction-return=thunk-extern support") which introduces the feature.
Supported values for this option are:
keep: do not convert function returns.thunk-extern: convert function returns (ret) to jumps (jmp) to an external symbol called__x86_return_thunk.
Like in Clang, GCC's values thunk and thunk-inline are not supported.
Only x86 and non-large code models are supported.