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From: "andi-gcc at firstfloor dot org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug lto/61969] [4.8/4.9/5 Regression] wrong code by LTO on i?86-linux-gnu (affecting trunk, 4.9.x, and 4.8.x)
Date: Tue, 07 Oct 2014 14:15:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61969

--- Comment #6 from Andi Kleen <andi-gcc at firstfloor dot org> ---
I looked at this a bit more. It's definitely the nrv pass that causes the
problem.

When I disable it in the source code the 32bit version compiles correctly.
I also tried disabling the next pass (cfgcleanup), but that didn't make a
difference.

It converts the local variable to be a value-expr.

It's still not exactly clear who deletes the variable declaration though.

There are two possibilities:
- nrv shouldn't convert the variable in the first place
- someone who messes with the variables forgets to check for value-exprs.

;; Function func_52 (func_52, funcdef_no=86, decl_uid=2858, cgraph_uid=54,
symbol_order=1152)

NRV Replaced: l_55  with: <retval>
func_52 (uint32_t p_53)
{
  extern const struct S0 l_55 = {.f0=4, .f1=40290, .f2=10, .f3=4} [value-expr:
<retval>];

  <bb 2>:
  return <retval>;

}