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Re: RTL

From: Jim Wilson <wilson at specifixinc dot com>
To: "Sruthy C.N" <csy2p100 at nitc dot ac dot in>
Cc: gcc at gcc dot gnu dot org
Date: Wed, 24 Sep 2003 21:51:30 -0700
Subject: Re: RTL
References: <2734.210.212.228.78.1064463025.webmail@ebox.nitc.ac.in>

Sruthy C.N wrote:

       In the RTL file (gcc version 3.2.2) there is some instructions(insn
6,8,10,12) which do some manipulations on esp..what is it doing?

As I mentioned in a previous message, it is aligning the stack in main to a 16 byte boundary. I believe this is for the MMX/SSE/SSE2 instructions, which are faster if the stack is 16 byte aligned. Some systems don't align the stack to 16 bytes at program startup, so we do it in main. This extra instruction only occurs in the main function.

If we consider the assembly program corresponding to this there is no such instructions corresponding to this..why?

Please give a testcase. I suspect you got your examples mixed up. Or maybe it got optimized away, though that seems unlikely. -- Jim Wilson, GNU Tools Support, http://www.SpecifixInc.com

Follow-Ups:
- Re: RTL
  - From: Sruthy C.N
- Re: RTL
  - From: Sruthy C.N

References:
- RTL
  - From: Sruthy C.N

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