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Date: Sun, 04 Sep 2005 16:26:00 -0000
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From: "rguenth at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
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Reply-To: gcc-bugzilla@gcc.gnu.org
Subject: [Bug middle-end/20408] Unnecessary code generated for empty structs
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X-SW-Source: 2005-09/txt/msg00437.txt.bz2
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------- Additional Comments From rguenth at gcc dot gnu dot org  2005-09-04 16:25 -------
For

struct Foo {};
void foo(const Foo&);
void bar(Foo);

void fooc(void)
{
        foo(Foo());
}
void barc(void)
{
        bar(Foo());
}

we get different initializers for the Foo& and the Foo case:

void fooc() ()
{
  struct Foo D.1594;

<bb 0>:
  D.1594 = {};
  foo (&D.1594);
  return;

}

void barc() ()
{
  struct Foo D.1613;

<bb 0>:
  D.1613 = 0;
  bar (D.1613) [tail call];
  return;

}

The former looks correct and does not produce initialization code
for the temporary.  The latter produces an unneccessary (uninitialized)
initialization of the pass-by-value stack slot on x86.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20408