Add TARGET_COMPUTE_MULTILIB hook to override multi-lib result.
Create a new hook to let target could override the multi-lib result,
the motivation is RISC-V might have very complicated multi-lib re-use
rule*, which is hard to maintain and use current multi-lib scripts,
we even hit the "argument list too long" error when we tried to add more
multi-lib reuse rule.
So I think it would be great to have a target specific way to determine
the multi-lib re-use rule, then we could write those rule in C, instead
of expand every possible case in MULTILIB_REUSE.
* Here is an example for RISC-V multi-lib rules:
https://gist.github.com/kito-cheng/
0289cd42d9a756382e5afeb77b42b73b
gcc/ChangeLog:
* common/common-target.def (compute_multilib): New.
* common/common-targhooks.h (default_compute_multilib): New.
* common/common-targhooks.cc (default_compute_multilib): New.
* doc/tm.texi.in (TARGET_COMPUTE_MULTILIB): New.
* doc/tm.texi: Regen.
* gcc.cc: Include common/common-target.h.
(set_multilib_dir) Call targetm_common.compute_multilib.
(SWITCH_LIVE): Move to opts.h.
(SWITCH_FALSE): Ditto.
(SWITCH_IGNORE): Ditto.
(SWITCH_IGNORE_PERMANENTLY): Ditto.
(SWITCH_KEEP_FOR_GCC): Ditto.
(struct switchstr): Ditto.
* opts.h (SWITCH_LIVE): Move from gcc.c.
(SWITCH_FALSE): Ditto.
(SWITCH_IGNORE): Ditto.
(SWITCH_IGNORE_PERMANENTLY): Ditto.
(SWITCH_KEEP_FOR_GCC): Ditto.
(struct switchstr): Ditto.