Re: [PATCH] Relax MIPS j/jal out-of-range check

[Paul Koning <pkoning at equallogic dot com>]

>>>>> "Daniel" == Daniel Jacobowitz <drow@false.org> writes:

 Daniel> On Tue, May 09, 2006 at 03:16:37PM +0100, Thiemo Seufer
 Daniel> wrote:
 >> Hello All,
 >> 
 >> I applied the appended patch. It relaxes the range checking for j
 >> and jal addresses to a warning, since there are a few cases where
 >> the effect of an out of range jump can be the intended result.

 Daniel> Why?  Especially bearing in mind that we're in the assembler
 Daniel> here.  This doesn't make sense to me.

If you have a routine that's sometimes called from uncached code, and
the label is a KSEG0 address, you could call it from KSEG1 code simply
with
	jal	label
and the machine will do the right thing (you end up at the KSEG1
address corresponding to "label").

It's a bit of a stretch, I suppose, but I've run into this.

Without the patch you end up having to do this:
	jal	label+0x20000000
or perhaps even uglier things, if that address arithmetic is invalid
here. 

      paul