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From: Philip Blundell <philb@gnu.org>
To: nobody@gcc.gnu.org
Cc: gcc-prs@gcc.gnu.org
Subject: Re: optimization/3978: arm peephole for loading two consecutive memory locations generates suboptimal code (on arm7tdmi)
Date: Thu, 09 Aug 2001 14:16:00 -0000	[thread overview]
Message-ID: <20010809211602.10052.qmail@sourceware.cygnus.com> (raw)

The following reply was made to PR optimization/3978; it has been noted by GNATS.

From: Philip Blundell <philb@gnu.org>
To: segher@chello.nl
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: optimization/3978: arm peephole for loading two consecutive memory locations generates suboptimal code (on arm7tdmi) 
Date: Thu, 09 Aug 2001 22:12:51 +0100

 --==_Exmh_1440650826P
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 >I often see generated code like
 >
 >add   temp, pointer, #offset
 >ldmia temp, {regA, regB}
 >
 >(after which temp is dead)
 >
 >which is slower than just
 >
 >ldr regA, [pointer, #offset]
 >ldr regB, [pointer, #offset+4]
 >
 >and wastes a register as well
 
 Use -mtune=arm8 or some such.  I don't think this will do any harm on 
 ARM7TDMI and it should yield the results you are looking for.
 
 p.
 
 
 
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             reply	other threads:[~2001-08-09 14:16 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2001-08-09 14:16 Philip Blundell [this message]
  -- strict thread matches above, loose matches on Subject: below --
2001-08-10  3:26 rearnsha
2001-08-09 12:56 segher

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