--- Nathan Sidwell <[EMAIL PROTECTED]> wrote:
> Sanjiv Kumar Gupta wrote:
>
> >
> > Thanks for a prompt reply, Nathan.
> > The add insn can take a symbol_ref, which is
> converted
> > to const_int during relocation. But I don't want
> to
> > allow expressions like (const:SI (plus:SI
> > symbol_ref:SI) (const_int)) in the insn.
> > How should I do that, do I need to implement
> > LEGITIMATE_CONST_P () accordingly?
>
> you could do that, but I don't understand why
> symref+const
> is not allowed. After all, you could have a
> different plain symref whose
> value was the original symbol+const.
>
> I.e. why is
> add r1,foo+10
> not allowed, but
> add r1,baz
> allowed. When linking baz could be defined as
> 'foo+10'. so what's going
> on?
>
> nathan
consider the second operand as an 8-bit offset
calculated by linker.
Now
add r1, foo
add r1, 10
add r1, -10
are okay but
add r1, foo + 10
add r1, -10
are not, since (foo + 10) may overflow during
relocation, so the value (foo + 10) && 0xff inserted
by linker is not correct.
Let me know if I am still not able to explain it.
Regards
--Sanjiv.
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