Simple example showing SSE instructions are generated for a target which disables MMX and SSE and enables soft-float.

cargo install xargo
xargo build --target no-xmm

The generated code for bar includes SSE instructions to save and restore the xmm6-15 registers for the win64 ABI. These instructions are not generated when extern "win64" is removed. This only happens in this example for debug builds, however, it occurs in release builds when the function contains cross-crate function calls.