GCC's softfloat is built by default without support for dynamic
rounding modes. This makes softfloat newlib's floating point always
round-to-zero, and returns a failure code when trying to set it.
This patch is needed to make newlib compile on anything without F, as
it used to try use an undefined instruction to do this.
"jump" was renamed to "tail" (as in tail call) and may freely clobber a
t-register, as before. A new "jump" was added that requires a second
argument, which is the scratch register it may clobber.
"tail" should be used for tail calls; "jump" should be used for
intraprocedural jumps more than 1 MiB away.
v0-1 are removed; arguments are now returned in a0-1. Registers are
renumbered so that s0-1 and a0-5 map to x8-15 to simplify the RVC ISA.
(These are the most popular 8 registers besides x0 and sp.)
Andrew Waterman
Scott Beamer
Palmer Dabbelt
Andrew Waterman