This is the mail archive of the gcc-help@gcc.gnu.org mailing list for the GCC project.

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]
Other format:	[Raw text]

Re: Question about -ftree-* optimizations in -O1

From: Jeff Law <law at redhat dot com>
To: Libin Dang <libin dot dang at windriver dot com>, Jiaqi Tan <jiaqi dot tan at gmail dot com>, gcc-help at gcc dot gnu dot org
Date: Fri, 17 Jun 2016 09:27:17 -0600
Subject: Re: Question about -ftree-* optimizations in -O1
Authentication-results: sourceware.org; auth=none
References: <CAPfiRNCBDtLakxJs1WWoSD3QCLR7q-xbqQ+WA+vPWpSB+KSu5Q at mail dot gmail dot com> <57635674 dot 20006 at windriver dot com>

On 06/16/2016 07:46 PM, Libin Dang wrote:



On 06/17/2016 06:39 AM, Jiaqi Tan wrote:

Hi,

What does the tree in "-ftree-*" refer to in the following
optimization flags that are turned on as part of -O1 in gcc? Does the
tree refer to an internal GCC data structure?


Yes. For further details please see:
https://gcc.gnu.org/onlinedocs/gccint/Tree-SSA.html

Correct.

Essentially before the introduction of tree-ssa all optimizers ofsignificance were written to optimize the lower level RTL IL. Theintroduction of the tree-ssa optimizers brought optimizations to thehigher tree/gimple IL.

The new optimizers needed switches and we prefixed all of them with-ftree. It may have been a bad choice since ultimately the users of GCCdon't much care about what IL a particular optimizer works on. But atthis point those options are set in stone.


jeff

References:
- Question about -ftree-* optimizations in -O1
  - From: Jiaqi Tan
- Re: Question about -ftree-* optimizations in -O1
  - From: Libin Dang

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]