Problem in .md(Machine Description) file

Problem in .md(Machine Description) file

[nitin jain]

Hi,

I have to write a machine description file for a chip.
For that, i am trying to understand the structure and
systex of the machine description file of i386.

My problem is that why a 'define_insn' with a name
that start with '*' is used. Is it used for generating
RTL insn or for other purpose?

for example:
-------------------------------------------------
(define_insn "*cmphi_minus_1"
  [(set (reg 17)
        (compare (minus:HI (match_operand:HI 0
"nonimmediate_operand" "rm,r")
                           (match_operand:HI 1
"general_operand" "ri,mr"))
                 (const_int 0)))]
  "ix86_match_ccmode (insn, CCGOCmode)"
  "cmp{w}\t{%1, %0|%0, %1}"
  [(set_attr "type" "icmp")
   (set_attr "mode" "HI")])
--------------------------------------------------
If it is used to generate RTL insn then what is the
difference between this and 'define_insn' with name
that does not start with '*'.

Waitinf for a prompt reply.
Thanks in advance.


=====
-------------------------------------------------------------------
Nitin Jain,                       
H-8 ,Room No: 24
I.I.T.Bombay, Powai, Mumbai.
Mail-id: nitin-mbm@yahoo.com 
         nitinj@cse.iitb.ac.in
-------------------------------------------------------------------

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RE: Problem in .md(Machine Description) file

[Rakesh Kumar - Software, Noida]

> This is what written in the GCC manual.
> My problem is that if these expressions are used to
> match generated RTL insn then
> 
> 1. What is the difference between these and the
> nameless 'define_insn'?
No difference, except that you would be able to know which nameless pattern
(the define_insn with *) is used to generate the RTL code. Without *, you
won't get what define_insn matched out of the nameless patterns. You see, it
only holds for debugging purposes.

> 
> 2. To match RTL code, that code should be generated by
> some other 'define_insn'.
> But the pattern in define_insn "*..." does not match
> with the other patterns in the whole .md file at all.
> This means that those RTL insn is not generated by any
> RTL expression
> in .md file. So what is the need to match them.
Sorry, I'm not able to get the point.......Please clarify

> 
> Waiting for reply.
> Nitin Jain
> CSE Dept. (IIT bombay)
>  
> > Regards,
> > Rakesh
> 
> 
> =====
> -------------------------------------------------------------------
> Nitin Jain,                       
> H-8 ,Room No: 24
> I.I.T.Bombay, Powai, Mumbai.
> Mail-id: nitin-mbm@yahoo.com 
>          nitinj@cse.iitb.ac.in
> -------------------------------------------------------------------
> 
> __________________________________
> Do you Yahoo!?
> Yahoo! SiteBuilder - Free, easy-to-use web site design software
> http://sitebuilder.yahoo.com
> 

RE: Problem in .md(Machine Description) file

[nitin jain]

> > Hi,
> > 
> > I have to write a machine description file for a
> chip.
> > For that, i am trying to understand the structure
> and
> > systex of the machine description file of i386.
> > 
> > My problem is that why a 'define_insn' with a name
> > that start with '*' is used. Is it used for
> generating
> > RTL insn or for other purpose?
> 
> The * in insn name is used for identifying the
> instruction in RTL dumps.
> These are no different from the nameless pattern.

This is what written in the GCC manual.
My problem is that if these expressions are used to
match generated RTL insn then

1. What is the difference between these and the
nameless 'define_insn'?

2. To match RTL code, that code should be generated by
some other 'define_insn'.
But the pattern in define_insn "*..." does not match
with the other patterns in the whole .md file at all.
This means that those RTL insn is not generated by any
RTL expression
in .md file. So what is the need to match them.

Waiting for reply.
Nitin Jain
CSE Dept. (IIT bombay)
 
> Regards,
> Rakesh


=====
-------------------------------------------------------------------
Nitin Jain,                       
H-8 ,Room No: 24
I.I.T.Bombay, Powai, Mumbai.
Mail-id: nitin-mbm@yahoo.com 
         nitinj@cse.iitb.ac.in
-------------------------------------------------------------------

__________________________________
Do you Yahoo!?
Yahoo! SiteBuilder - Free, easy-to-use web site design software
http://sitebuilder.yahoo.com

RE: Problem in .md(Machine Description) file

[Rakesh Kumar - Software, Noida]

> -----Original Message-----
> From: nitin jain [mailto:nitin_mbm@yahoo.com]
> Sent: Friday, August 22, 2003 4:56 PM
> To: gcc-help@gcc.gnu.org
> Subject: Problem in .md(Machine Description) file
> 
> 
> Hi,
> 
> I have to write a machine description file for a chip.
> For that, i am trying to understand the structure and
> systex of the machine description file of i386.
> 
> My problem is that why a 'define_insn' with a name
> that start with '*' is used. Is it used for generating
> RTL insn or for other purpose?

The * in insn name is used for identifying the instruction in RTL dumps.
These are no different from the nameless pattern.

Regards,
Rakesh