rtx structure

Bharati Bhole bharati.bhole@gmail.com
Mon Nov 6 14:03:00 GMT 2006


On 11/6/06, Andrew Haley <aph@redhat.com> wrote:
> Bharati Bhole writes:
>  > On 11/6/06, Andrew Haley <aph@redhat.com> wrote:
>  > > Bharati Bhole writes:
>  > >  > On 11/2/06, Andrew Haley <aph@redhat.com> wrote:
>  > >  > > Bharati Bhole writes:
>  > >  > >  > On 11/2/06, Daniel Berlin <dberlin@dberlin.org> wrote:
>  > >  > >  > > > I want to know what part of rtx each field in this structure stores.
>  > >  > >  > > > While tracing through gdb i tried to print the rtx, and i was not able
>  > >  > >  > > > to understand that. Could u please explain me it with a sample RTX
>  > >  > >  > > > that what value these fields have.
>  > >  > >  > > >
>  > >  > >  > >
>  > >  > >  > > The macros used to access the rtl fields in rtl.h explain what part of
>  > >  > >  > > each field they access and what they treat that object as.
>  > >  > >  > >
>  > >  > >  > > The definitions of rtl in rtl.def define what each portion of a piece
>  > >  > >  > > of valid RTL is structured as.
>  > >  > >  > > > Bharati.
>  > >  > >  > > >
>  > >  > >  > >
>  > >  > >  >
>  > >  > >  > I have gone through the structure but i still dont get it.
>  > >  > >  > Could anybody please tell me, if the following insn is  a sample insn,
>  > >  > >  > how will the rtx structure look like -
>  > >  > >  >         (define_insn "subsi3_carry_zext"
>  > >  > >  >         [(set (match_operand:DI 0 "register_operand" "=rm,r")
>  > >  > >  >                  (zero_extend:DI
>  > >  > >  >                (minus:SI (match_operand:SI 1 "register_operand" "0,0")
>  > >  > >  >                           (plus:SI (match_operand:SI 3
>  > >  > >  > "ix86_carry_flag_operator" "")
>  > >  > >  >                               (match_operand:SI 2 "general_operand" "ri,rm")))))
>  > >  > >  >           (clobber (reg:CC FLAGS_REG))]
>  > >  > >  >        "TARGET_64BIT && ix86_binary_operator_ok (MINUS, SImode, operands)"
>  > >  > >  >        "sbb{l}\t{%2, %k0|%k0, %2}"
>  > >  > >  >       [(set_attr "type" "alu")
>  > >  > >  >       (set_attr "pent_pair" "pu")
>  > >  > >  >       (set_attr "mode" "SI")])
>  > >  > >
>  > >  > > But this isn't a simple insn, it's a machine description pattern.
>  > >  > > These are described in Section 13, Machine Descriptions.
>  > >
>  > >  > Yes, this is a machine description pattern. In the genrecog.c file the
>  > >  > .md file is read and from each insn the RTL template is filled in the
>  > >  > RTX structure. So i want to know that how this insn ie the RTL teplate
>  > >  > from this insn will be filled in the RTX structure. I mean what part
>  > >  > of the template, each field of RTX structure will store? Could anybody
>  > >  > please tell me that?
>  > >
>  > > Possibly, but it would be better for you to find out for yourself.
>  > > Have you tried putting a breakpoint on make_insn_raw ?
>
>  > The project we are dealing with is related to RTL to ASM conversion
>  > only. This make_insn_raw exists in emit-rtl.c. While debugging
>  > genrecog i tried to print the RTX structure but didn't understand. So
>  > please explain it to me for above insn.
>
> What, all of it?
>
> Show me the debug_rtx of the insn that was generated when you were
> debugging.
>
> Andrew.
>

This is what i got when i traced through gdb and tried to print RTX structure.

 desc = read_md_rtx (&pattern_lineno, &next_insn_code);
(gdb) n
2745          if (desc == NULL)
(gdb)
2748          switch (GET_CODE (desc))
(gdb) p *desc
$1 = {code = 154, mode = VOIDmode, jump = 0, call = 0, unchanging = 0,
volatil = 0, in_struct = 0, used = 0,
  frame_related = 0, return_val = 0, u = {fld = {{rt_int = 134674728,
rt_uint = 134674728, rt_str = 0x806f928 "cpu",
        rt_rtx = 0x806f928, rt_rtvec = 0x806f928, rt_type = 134674728,
rt_addr_diff_vec_flags = {min_align = 40,
          base_after_vec = 1, min_after_vec = 0, max_after_vec = 0,
min_after_base = 1, max_after_base = 1,
          offset_unsigned = 1, scale = 6}, rt_cselib = 0x806f928,
rt_bit = 0x806f928, rt_tree = 0x806f928,
        rt_bb = 0x806f928, rt_mem = 0x806f928, rt_reg = 0x806f928}},
hwint = {134674728}}}

Bharati.



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