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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] [4544] added tcg_temp_free() and improved the
	handling of constants
Date: Fri, 23 May 2008 19:03:35 +0100
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To: qemu-devel@nongnu.org

> added tcg_temp_free() and improved the handling of constants

Should the return value of tcg_const_i32 et. al. be considered immutable, or 
is it ok to use it as a temporary?

e.g.:

static TCGv do_frob(TCGv base, int addend)
{
  TCGv tmp = tcg_const_i32(addend);
  tcg_gen_helper_frob(tmp, tmp, base)
  return tmp;
}

or should this be written as:

static TCGv do_frob(TCGv base, int addend)
{
  TCGv tmp = tcg_temp_new(TCG_TYPE_I32);
  tcg_gen_movi_i32(tmp, addend);
  tcg_gen_helper_frob(tmp, tmp, base)
  return tmp;
}

Currently it's fairly hard to enforce this restriction automatically, but we 
need to decide whether it's a feature or a bug.

Paul