Re: i370 port

["Paul Edwards" <mutazilah at gmail dot com>]

> > > As an alternative to the operand predicate, you might also add
> > > an extra check to the insn condition.  For example, something
> > > along the following lines should work:
> > >
> > > (define_insn ""
> > >   [(set (match_operand:SI 0 "register_operand" "=d")
> > >         (mult:SI (match_operand:SI 1 "register_operand" "0")
> > >                  (match_operand:SI 2 "const_int_operand" "K")))]
> > >   "CONST_OK_FOR_LETTER_P (INTVAL (operands[2]), 'K')"
> >
> > My eyes lit up when I saw that!  However, it produced a compiler
> > error when I tried it.  But undeterred, I tried this:

Sorry.  I just copied the last line into the existing pattern, didn't
notice that you'd changed the predicate too.

> > (define_insn ""
> >   [(set (match_operand:SI 0 "register_operand" "=d")
> >         (mult:SI (match_operand:SI 1 "register_operand" "0")
> >                  (match_operand:SI 2 "immediate_operand" "K")))]
> >   "(GET_CODE (operands[2]) == CONST_INT
> >    && REG_P (operands[0])
> >    && CONST_OK_FOR_LETTER_P (INTVAL (operands[2]), 'K'))"
>
> Huh.  Instead of adding an explicit CONST_INT check, my approach
> above used a const_int_operand predicate (instead of immediate_operand).
> That should have had the exact same effect ...   I'm not sure why the
> REG_P check on the other operand would be necessary at this point.

I just copied that from the existing condition too.  Once I realised
that I could put a check in advance, I just copied the check
across basically.  I'd seen that before, it just hadn't sunk in that
I could use it for this situation.

I will try out your original suggestion again properly.  :-)

> > And it worked (verified by self-compile)!  And I relaxed the
> > constraint on the "M" instruction as well.  Those old warnings
> > are apparently irrelevant now.  Thank you sir.  :-)
>
> OK, that's good to know.

Indeed.

And as I mentioned, there's just one real bug that I know of left.  I can
bypass the bug in the GCC code that I am compiling, by forcing a
function call.

C:\devel\gccnew\gcc>gccmvs -DUSE_MEMMGR -Os -S -ansi -pedantic-errors -DHAVE_CON
FIG_H -DIN_GCC -DPUREISO -I ../../pdos/pdpclib -I . -I config/i370 -I 
../include
        varasm.c
varasm.c: In function `force_const_mem':
varasm.c:3021: internal compiler error: in instantiate_virtual_regs_lossage, 
at
function.c:3765
Please submit a full bug report,
with preprocessed source if appropriate.
See <URL:http://gccmvs.sourceforge.net> for instructions.

This is the code that is triggering off that bug:

force_const_mem (enum machine_mode mode, rtx x)
{
 int hash;
 struct constant_descriptor_rtx *desc;
...
   if (compare_constant_rtx (mode, x, desc))


static int
compare_constant_rtx (enum machine_mode mode, rtx x,
^I^I      struct constant_descriptor_rtx *desc)
{
 struct rtx_const value;

 decode_rtx_const (mode, x, &value);

 /* Compare constant contents.  */
#if defined(XTARGET_MVS) /* +++ seems we have a machine definition problem 
*/
 return (memcmp) (&value, &desc->value, sizeof (struct rtx_const)) == 0;
#else
 return memcmp (&value, &desc->value, sizeof (struct rtx_const)) == 0;
#endif
}


You can see how I normally work around this problem by forcing a
function call.

If I do that force, then I get this code generated:

L445     EQU   *
        LTR   3,3
        BE    L442
        MVC   88(4,13),0(11)
        MVC   92(4,13),4(11)
        LA    2,560(,13)
        ST    2,96(13)
        LA    1,88(,13)
        L     15,=A(@@F17)
        BALR  14,15
        ST    2,88(13)
        LR    2,3
        A     2,=F'8'
        ST    2,92(13)
        MVC   96(4,13),=F'196'
        LA    1,88(,13)
        L     15,=V(MEMCMP)
        BALR  14,15
        LTR   15,15

which is bizarre.  It seems to be comparing two values that are 8 bytes
apart, for a length of 196.  Can't imagine that doing anything useful.

It's almost certainly an i370 port bug, but I haven't had any bright
ideas on how to fix that yet.  :-)

BFN.  Paul.