From: Zdenek Dvorak <rakdver@atrey.karlin.mff.cuni.cz>
To: Revital Eres <ERES@il.ibm.com>
Cc: gcc@gcc.gnu.org
Subject: Re: loop unroll question
Date: Fri, 02 Apr 2004 09:06:00 -0000 [thread overview]
Message-ID: <20040402090636.GA19675@atrey.karlin.mff.cuni.cz> (raw)
In-Reply-To: <OF3FEBFE03.6A98C185-ONC2256E69.004E2096-C2256E69.004F31D6@il.ibm.com>
Hello,
> For mainline on power-pc 4 with the option -O3 -funroll-loops,
> the following loop is not unrolled, but in GCC 3.4 it is.
> Also for mainline the bct is not inserted, but again in GCC 3.4
> it is.
>
> void
> example_new(int a[],int b[],int c[], int j)
> {
> int i;
>
> for(i=0 ; i<=j ; i++)
> {
> c[i]=a[i]+b[i];
> }
> return;
> }
as for inserting bct -- it was wrong to do this, since the loop could
be the infinite one (not really, since we work in a signed arithmetics
for that the overflow has an undefined behavior, but we cannot
verify this on rtl level).
As for unrolling, we are too conservative here; I will send a patch
for this soon.
Zdenek
> If the condition is changed to < (instead of <=) the unrolling is
> done as expected and bct is inserted.
>
> Thanks,
> Revital
next parent reply other threads:[~2004-04-02 9:06 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <OF3FEBFE03.6A98C185-ONC2256E69.004E2096-C2256E69.004F31D6@il.ibm.com>
2004-04-02 9:06 ` Zdenek Dvorak [this message]
2004-04-01 14:53 Revital Eres
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