Re: gcc port to StarCore

["David Livshin" <dlivshin at internet-zahav dot net>]

----- Original Message -----
From: Alan Lehotsky <apl@alum.mit.edu>
To: David Livshin <dlivshin@zahav.net.il>
Cc: <gcc@gcc.gnu.org>
Sent: Thursday, May 02, 2002 2:20 PM
Subject: Re: gcc port to StarCore


> At 8:38 AM +0200 5/2/02, David Livshin wrote:
> >
> >  > Can you post the define_expand and/or define_insn for these?
> >>
> >
> >You are right - the pattern is:
> >
> >
> >( define_expand "cmpsi"
> >   [ ( set ( cc0 )
> >       ( compare ( match_operand:SI 0 "drREG_operand" "d,z" )
> >                 ( match_operand:SI 1 "drREG_operand" "d,z" )
> >       )
> >     )
> >   ]
> >   ""
> >   "
> >   {
> >    StarCore_DefineExpand_cmp( operands, FALSE, FALSE );
> >    DONE;
> >   }"
> >)
>
>
> Well, this would prevent the initial generation of compares with
> literals as operands - but for most ports, the compiler will
> initially "load" literals into pseudo-registers ANYWAY and let the
> various optimization passes figure out which things are better off as
> immediate values.
>
> I should have just asked for your DEFINE_INSN that matches the
> compare patterns.   Also, you
> use a function to actually generate the RTL - so I can't see what
> sort of RTL you're really producing
> or consuming!

StarCore_DefineExpand_cmp( operands, FALSE, FALSE );

is just saving operands and data about comapre ( e.g. is it FloatingPoint
compare ):


void StarCore_DefineExpand_cmp( rtx *operands, bool Is_FP, bool Is_TST )
 {

  StarCore_cmp.op0 = operands[0];
  StarCore_cmp.op1 = operands[1];
  StarCore_cmp.IsFP = Is_FP;
  StarCore_cmp.IsTST = Is_TST;

 }    /*    StarCore_DefineExpand_cmp    */


>
> How about posting:
>
> 1/ The rtl dump for your simple example - the first one, and
> possibly the
>      combine dump.

Will gladly do that if my guess ( that follows ) is wrong.

>
> 2/ the DEFINE_INSNs for compares

after expanding "cmpsi" as described above I expand conditional jumps ( e.g.
"bgt" ) emitting, among other things,

     emit_insn( gen_cmpsiEXPANDED( StarCore_cmp.op0, StarCore_cmp.op1,
                                    GEN_INT( ( int )cndt_code ),
                                    gen_reg_rtx( SImode ) ) );

where:


( define_insn "cmpsiEXPANDED"
  [ ( parallel [ ( unspec:SI [ ( match_operand:SI 0 "drREG_operand" "d,z" )
                               ( match_operand:SI 1 "drREG_operand" "d,z" )
                               ( match_operand:SI 2 "immediate_operand" "" )
                             ]
                             UNSPEC_CMPsi
                 )
                 ( set ( cc0 ) ( match_operand:SI 3 "" "" ) )
               ]
    )
  ]
  ""
  "* return (char *)StarCore_DefineInsn_cmpsi( operands, insn );"
)

with StarCore_DefineInsn_cmpsi being routine that just emits StarCore
machine code.

Is "unspec' what is preventing constant holding in compare?