MIPS .reginfo section provides information on the registers used by the code in the object file. Linker should collect this information and write a single .reginfo section in the output file. This section contains a union of used registers masks taken from input .reginfo sections and final value of the _gp symbol.
For details see the "Register Information" section in Chapter 4 in the following document:
The patch implements .reginfo sections handling with a couple missed features: a) it does not put output .reginfo section into the separate REGINFO segment; b) it does not merge ri_cprmask masks from input section. These features will be implemented later.