Patch to rs6000/eabispe.h and rs6000/linuxspe.h to disallow -m64

[Daniel Jacobowitz]

On Thu, Oct 14, 2004 at 03:32:22PM -0400, Aldy Hernandez wrote:
> On Thu, Oct 14, 2004 at 06:36:57PM +0000, Joseph S. Myers wrote:
> > powerpc-eabispe and powerpc-linuxspe should not support -m64, but
> > wrongly permitted that option.  Fixed thus.
> > 
> > Cross tested with no regressions to powerpc-eabispe, and tested that
> > cc1 builds and produces the proper messages for powerpc-linuxspe.  OK
> 
> OK.
> 
> > to commit?  (Testing was done on 3.4 branch because of a pre-existing 
> > build failure for powerpc-eabispe on mainline.  The same patch will apply 
> > without changes to both mainline and 3.4 branch.)
> 
> Poop.  I was hoping you had addressed this :-).

[Geoff, this is in reference to:
  http://gcc.gnu.org/ml/gcc/2004-08/msg00307.html
]

I took a look at it.  The problem is that movdi32_internal has two
workable alternatives for the failing instruction: r->o<> or f->m.
In each case one side matches precisely and the other side matches with
a reload; REJECT gets a +2 for the reload.  One of the reloads is a
reload for input and the other is a reload for output; therefore,
reload prefers the possibility with an input reload.

So reload picks f->m.  Obviously this will fail - there are no avaiable
registers in class FLOAT_REGS.  This patch tells reload this, forcing
rejection of FPR constraints by mapping 'f' to NO_REGS.  Untested other
than that one testcase; Aldy offered to give it a spin.

Like Geoff wrote in his response to Aldy in August, this is a
suspicious choice for reload to make.  Another way to fix this would be
to not penalize output reloads which are only for the memory address;
those are no more or less likely to be reused than memory address
reloads on an input.  Yet another way would be to penalize the f->m
alternative in the rs6000 backend.  Yet another would be to have a
target hook to determine how much to reject by.  But I think this patch
will do for now.

-- 
Daniel Jacobowitz

2004-10-14  Daniel Jacobowitz  <dan@codesourcery.com>

	* config/rs6000/rs6000.h (REG_CLASS_FROM_LETTER): Return NO_REGS
	for 'f' if !TARGET_FPRS.

Index: rs6000.h
===================================================================
RCS file: /home/drow/rsync/gcc-cvs/gcc/gcc/config/rs6000/rs6000.h,v
retrieving revision 1.340
diff -u -p -r1.340 rs6000.h
--- rs6000.h	23 Sep 2004 14:34:29 -0000	1.340
+++ rs6000.h	14 Oct 2004 20:43:45 -0000
@@ -1283,7 +1283,7 @@ enum reg_class
 /* Get reg_class from a letter such as appears in the machine description.  */
 
 #define REG_CLASS_FROM_LETTER(C) \
-  ((C) == 'f' ? FLOAT_REGS	\
+  ((C) == 'f' ? (TARGET_FPRS ? FLOAT_REGS : NO_REGS)	\
    : (C) == 'b' ? BASE_REGS	\
    : (C) == 'h' ? SPECIAL_REGS	\
    : (C) == 'q' ? MQ_REGS	\