Kenneth Zadeck - Re: Link-time optimzation (original) (raw)

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• From: Kenneth Zadeck
• To: Ian Lance Taylor
• Cc: gcc mailing list
• Date: Thu, 17 Nov 2005 11:16:56 -0500 (EST)
• Subject: Re: Link-time optimzation
• Reply-to: Kenneth dot Zadeck at NaturalBridge dot com

Mark Mitchell mark@codesourcery.com writes:

http://gcc.gnu.org/projects/lto/lto.pdf

Section 4.2 (Executable Representation) describes the GVM as a stack machine, and mentions load, store, duplicate, and swap operations. But it also discusses having registers which correspond to GIMPLE local variables. The way I put this together is that a MODIFY_EXPR which sets a local variable, say, will be converted to something that computes the expression using a stack and then assigns the value to a register. It's easy to see how to convert such a MODIFY_EXPR into a stack machine and back. But it's not easy to see why that stack machine is going to need, e.g, a swap operation. There is no GIMPLE swap operator. So I may still be confused about something.

You are most likely correct. We either do not need a swap or do not want to encourage people to try to optimize the trees so much that they need a swap.

Ian

• References:
  • Re: Link-time optimzation
    * From: Ian Lance Taylor