* lightening/arm-cpu.c (rotate_left): Fix the case of rotating by zero,
which produced undefined behavior. Many thanks to Andrew
Gierth (andrew at tao11 riddles org uk) for the debugging and the
fix.
It is unlikely for any ARM code to be close enough to not have needed
a veneer, but it is possible, especially if running in a program with
another JIT library.
The existing calli / callr interface is for ABI calls. Sometimes though
you want to call some of your own code, just to get the current return
address. ARM's branch-and-link instructions are ideal for this but they
don't exist on x86; there we emulate them by adding corresponding
pop_link_register / push_link_register instructions that are no-ops on
ARM.
* lightening.h (FOR_EACH_INSTRUCTION): Add jit_jmpi_with_link,
pop_link_register, push_link_register.
* lightening/arm-cpu.c:
* lightening/x86-cpu.c:
* lightening/aarch64-cpu.c (jmpi_with_link, push_link_register)
(pop_link_register): Add implementations.
* lightening/arm.h:
* lightening/aarch64.h:
* lightening/x86.h (JIT_LR): New definition.
* tests/link-register.c: New test.
These operations emit the same code that GCC does for corresponding
operations under the sequential consistency memory model. It would be
possible to relax to acquire/release or something in the future.
This improves integration with other projects. Like for example Guile
already has files named jit.c and jit.h; it's easier to manage if
lightening uses its own file names.
