[PATCH] Fix mfcr for POWER targets other than POWER4

Troy Rollo troy@corvu.com.au
Sun Nov 5 23:49:00 GMT 2006

On Monday 06 November 2006 10:10, Alan Modra wrote:
> On Fri, Nov 03, 2006 at 06:27:02PM +1100, Troy Rollo wrote:
> > The patch at
> > <http://sources.redhat.com/ml/binutils/2003-07/msg00094.html> introduced
> > an alternative (faster) mfcr instruction for POWER4 targets, however the
> > flags were changed on the old instruction so that it was no longer
> > available when targeting POWER architectures other than POWER4.
> Eh?  The old single operand is still available.  What makes you think
> otherwise?  Please write a little testcase and "as" invocation to show
> what you mean.

If you just run "as -mpwr" on a file with that instruction in it you'll get 
the error. What makes me think "otherwise" is that I actually encountered 
this problem building GCC (which is still a mess for other reasons) on an AIX 
system using the GNU assembler, and traced through it to find that neither 
mfcr instruction was being included in the hash table of instructions.

In such cases older versions of gas work, and the bundled assembler works.

> > You can see some of the problems this has caused by googling for
> > "Unrecognized opcode mfcr".
> All I see is people using the wrong assembler, and cases where the new
> insn wasn't available.

A lot of the results are in building GCC (although in some cases it's not 
immediately apparent that that's what was being done since the GCC build was 
triggered by attempting to build something else). By the stage where the 
error occurs it's already proven that the right assembler is being used since 
it's already been used to build a whole bunch of other files.
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