Re: Problem with modyfying "addsi3" in machine description

[Tomasz Jankowski <tomcioj at gmail dot com>]

Thank you for answering your email.

I actually cannot use you suggestion, because source register and
destination register are almost always the same register. Now I'm
found something weird. Original template "addsi3" for OpenRISC is:

   (define_insn "addsi3"
     [(set (match_operand:SI 0 "register_operand" "=r,r")
       (plus:SI (match_operand:SI 1 "register_operand" "%r,r")
   	 (match_operand:SI 2 "nonmemory_operand" "r,I")))]
    ""
    "@
     l.add   \t%0,%1,%2
     l.addi  \t%0,%1,%2"
    [(set_attr "type" "add,add")
     (set_attr "length" "1,1")])

and "mulsi3" is:

   (define_insn "mulsi3"
     [(set (match_operand:SI 0 "register_operand" "=r")
           (mult:SI (match_operand:SI 1 "register_operand" "r")
                    (match_operand:SI 2 "register_operand" "r")))]
     "TARGET_HARD_MUL"
     "l.mul   \t%0,%1,%2"
     [(set_attr "type" "mul")
      (set_attr "length" "1")])

Now, when I write in C such code:

   int b = 100;
   b *= 101;

GCC properly moves immediate to temporary register and then call
"l.mul" instruction. I tried to do the same trick and modified
"addsi3" template to:

   (define_insn "addsi3"
     [(set (match_operand:SI 0 "register_operand" "=r")
       (plus:SI (match_operand:SI 1 "register_operand" "%r")
   	 (match_operand:SI 2 "register_operand" "r")))]
    ""
    "l.add  \t%0,%1,%2"
    [(set_attr "type" "add")
     (set_attr "length" "1")])

The problem is that, GCC fails to compile with this modified template
with error:
   ../../gcc-4.5.1/gcc/crtstuff.c: In function â__do_global_dtors_auxâ:
   ../../gcc-4.5.1/gcc/crtstuff.c:332:1: internal compiler error: in
gen_add2_insn, at optabs.c:4764

As I remember documentation for RTL says, that it's able to make
operands fit instruction template, so it's able to move immediate to
register as it's done for "multsi3". So why it doesn't work for
"addsi3"?