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Re: loop unrolling, flags and passes

From: Ian Lance Taylor <iant at google dot com>
To: Abdul Wahid Memon <engrwahidmemon at gmail dot com>
Cc: "Kevin P. Fleming" <kpfleming at digium dot com>, gcc-help at gcc dot gnu dot org
Date: Mon, 13 Dec 2010 13:22:38 -0800
Subject: Re: loop unrolling, flags and passes
References: <AANLkTinVsfidr1SV2AZOZ5S7Y_sTN5GJwmhyz2wX1cEt@mail.gmail.com> <4D057AE6.6030201@digium.com> <AANLkTikc304x5k88c48iU7hg0r4EXZLY09ub8MVXQJya@mail.gmail.com>

Abdul Wahid Memon <engrwahidmemon@gmail.com> writes:

> Thanks for the response but I still didnt got the answer regarding
> whether it is possible to do loop unrolling without using -O1, -O2 or
> -O3. What exactly are those flags (along with funroll-all-loops) which
> makes loops unroll?

The -O options enable some compiler infrastructure, such as the
conversion to SSA form, that are required by the loop optimization
passes.  If the -O options are not used, the infrastructure is not
built, and the loop optimization passes, which depend on that
infrastructure, can not be run.

Ian

References:
- loop unrolling, flags and passes
  - From: Abdul Wahid Memon
- Re: loop unrolling, flags and passes
  - From: Kevin P. Fleming
- Re: loop unrolling, flags and passes
  - From: Abdul Wahid Memon

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