https://gcc.gnu.org/bugzilla/show_bug.cgi?id=74563
Jeffrey A. Law <law at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2017-04-14
Ever confirmed|0 |1
--- Comment #5 from Jeffrey A. Law <law at redhat dot com> ---
So what's happening here is the compact-branch support broke mips16.
It's pretty obvious if we look at mips.md:
(define_insn "*<optab>"
[(any_return)]
""
{
operands[0] = gen_rtx_REG (Pmode, RETURN_ADDR_REGNUM);
return mips_output_jump (operands, 0, -1, false);
}
[(set_attr "type" "jump")
(set_attr "mode" "none")])
;; Normal return.
(define_insn "<optab>_internal"
[(any_return)
(use (match_operand 0 "pmode_register_operand" ""))]
""
{
operands[0] = gen_rtx_REG (Pmode, RETURN_ADDR_REGNUM);
return mips_output_jump (operands, 0, -1, false);
}
[(set_attr "type" "jump")
(set_attr "mode" "none")])
Where RETURN_ADDR_REGNUM is always 31, even on mips16. So no matter what if we
generate any of the return insns matching those patterns we'll emit a jr $31.
I'm not familiar with this aspect of the MIPS port (it's 15+ years since I've
done any serious MIPS work), but ISTM that at least for the _internal version
we shouldn't be overwriting operands[0] -- whatever generates that pattern
should be passing us the right register.
For return and simple_return, we might need to conditionalize the assignment to
operands[0] since the return register is not provided.
