From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Michael P. Hayes" <michaelh@ongaonga.chch.cri.nz>
To: egcs@cygnus.com
Subject: Loop optimisation
Date: Tue, 04 Nov 1997 19:30:00 -0000
Message-id: <199711050335.QAA19282@ongaonga.chch.cri.nz>
X-SW-Source: 1997-11/msg00167.html

I've noticed that GCC poorly optimises the following loops:

void foo(const float *src, float *dst, int size, int offset)
{
    int i;

    for (i = 0; i < size; i++)
      dst[i + offset] = src[i];
}

where the loop RTL of interest after CSE is

  (set (reg:SI 43) (plus:SI (reg/v:SI 40) (reg/v:SI 42)))
  (set (reg:SI 44) (plus:SI (reg/v:SI 37) (reg:SI 43)))
  (set (mem/s:SF (reg:SI 44)) (reg:SF 45))

where 40 is i, the induction variable pseudo
      42 is offset
      37 is &dst 

Ideally, the redundant address calculations should be hoisted out of
the loop.  Is this within the scope of the current loop optimiser?

Michael.