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Date: Thu, 01 Oct 2009 14:41:00 -0000
From: Jean-Marc Saffroy <jean-marc.saffroy@joguin.com>
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To: cgen@sourceware.org
Subject: problem with 64-bit arch
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Hi,

I am trying to use CGEN for an experimental 64-bit architecture (ie. 
word-bitsize is 64), and in my case the generated arch-ibld.c file is 
incorrect.

I defined the following insn field:

(df f-disp24     "disp24"              (PCREL-ADDR) 8 24 INT
     ((value pc) (sra WI (sub WI value pc) (const 2)))
     ((value pc) (add WI (sll WI value (const 2)) pc))
)

(define-operand
   (name disp24)
   (comment "24 bit signed displacement")
   (type h-iaddr)
   (mode WI)
   (index f-disp24)
)

And arch-ibld.c contains the following code (in <arch>_cgen_insert_operand):

   switch (opindex)
     {
     case <ARCH>_OPERAND_DISP24 :
       {
         long value = fields->f_disp24;
         value = (() (((value) - (pc))) >> (2));
         errmsg = insert_normal (cd, value,
0|(1<<CGEN_IFLD_SIGNED)|(1<<CGEN_IFLD_PCREL_ADDR), 0, 8, 24, 32,
total_length, buffer);
       }
       break;

Note the missing type in the cast before assigning to value. Also using 
a long type for value will cause problems when running on a 32-bit host, 
since it operates on 64-bit values.

I had a quick look at the other two archs that use word-bitsize 64, ie. 
sparc64 and ia64, and it seems they use multi-ifields for this kind of 
PC-relative field, which may be an artificial way of avoiding the problem.

Is there an obvious fix to this problem?

Cheers,
JM