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Re: [patch] genrecog.c: Simplify comparisons against smallconstants in insn-recog.c.

From: Kazu Hirata <kazu at cs dot umass dot edu>
To: zack at codesourcery dot com
Cc: gcc-patches at gcc dot gnu dot org
Date: Thu, 29 Jan 2004 03:22:49 -0500 (EST)
Subject: Re: [patch] genrecog.c: Simplify comparisons against smallconstants in insn-recog.c.
References: <20040129.025306.63118625.kazu@cs.umass.edu><87isivi3db.fsf@egil.codesourcery.com>

Hi Zack,

> > Attached is a patch to simplify comparisons against small constants in
> > insn-recog.c by replacing
> >
> >   if (GET_CODE (x3) == CONST_INT
> >       && XWINT (x3, 0) == 10L
> >       && ...
> >
> > with
> >
> >   if (x3 == const_int_rtx[MAX_SAVED_CONST_INT + (10)]
> 
> Uhh... that doesn't look equivalent to me.

Why?  Is there a corner case or something?  gen_rtx_CONST_INT starts
out with...

rtx
gen_rtx_CONST_INT (enum machine_mode mode ATTRIBUTE_UNUSED, HOST_WIDE_INT arg)
{
  void **slot;

  if (arg >= - MAX_SAVED_CONST_INT && arg <= MAX_SAVED_CONST_INT)
    return const_int_rtx[arg + MAX_SAVED_CONST_INT];

Kazu Hirata

References:
- [patch] genrecog.c: Simplify comparisons against small constantsin insn-recog.c.
  - From: Kazu Hirata
- Re: [patch] genrecog.c: Simplify comparisons against smallconstants in insn-recog.c.
  - From: Zack Weinberg

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