Re: [PATCH/MIPS] Fix Branches with a constant offset

[Richard Sandiford <rdsandiford at googlemail dot com>]

Andrew Pinski <andrew.pinski@caviumnetworks.com> writes:
> Hi,
>   After:
> 2011-04-20  Catherine Moore  <clm@codesourcery.com>
>             David Ung <davidu@mips.com>..
>         * config/mips.c (mips_cl_insn): Add new field complete_p
> ...
>         (append_insn): Move O_constant expression handling.
>
> branches with a constant expression are broken by adding a relocation to them.
> The relocation is totally wrong as it is saying it is an absolute
> address while what we have really is an offset.
>
> This patch fixes the issue with how complete_p is handled for
> O_constant expression handling just like it was handled before this
> patch.
>
> OK?  Tested on mips64-linux-gnu with no regressions.

Oops.  It's certainly unfortunate that we've changed the meaning
of this case.  TBH though, the new version makes more sense to me.
If you really want a constant offset, ". + X" is (and IMO always was)
the right way to write it.  The old behaviour gave oddities where:

	.equ	x,0x1000
        beq     $4,$5,x

would treat "x" as an offset while:

        beq     $4,$5,x
	.equ	x,0x1000

would treat it as an address.  The new behaviour also seems to be
consistent with other targets.

None of which would be a convincing argument to change the behaviour
for its own sake.  But now that we've changed it anyway -- in at least
two releases -- I'm not sure we should go back.

Richard