[Bug ipa/99122] [10 Regression] ICE in force_constant_size, at gimplify.c:733

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99122

--- Comment #34 from Richard Biener <rguenth at gcc dot gnu.org> ---
interestingly I see

  a.9_70 = .builtin_alloca_with_align (iftmp.8_1, 8);
  (*a.9_70) = inline22.get_zero (); [static-chain: &FRAME.20] [return slot
optimization]

so there's no WITH_SIZE_EXPR, but the return value ends up done by reference:

        leaq    -80(%rbp), %rdx
        movq    %rdx, %r10
        movq    %rax, %rdi
        call    inline22__get_zero.0
        movq    %rbx, %rsp
        movq    -8(%rbp), %rbx
        leave

so I wonder if omitting DECL_BY_REFERENCE is simply a bug?  I mean the
ABI of the callee must be aware and it seems CALL_EXPR_RETURN_SLOT_OPT
is set by gimplification.  IIRC CALL_EXPR_RETURN_SLOT_OPT also only means
we _may_ return by reference not that we must.

/* In a CALL_EXPR, means that it's safe to use the target of the call
   expansion as the return slot for a call that returns in memory.  */
#define CALL_EXPR_RETURN_SLOT_OPT(NODE) \
  (CALL_EXPR_CHECK (NODE)->base.private_flag)

But of course if we do not exercise the return slot opt then there definitely
is a WITH_SIZE_EXPR missing.  Unless I'm missing somehting ...

The gimplifier code checks

              else if (TREE_CODE (*to_p) != SSA_NAME
                      && (!is_gimple_variable (*to_p)
                          || needs_to_live_in_memory (*to_p)))
                /* Don't use the original target if it's already addressable;
                   if its address escapes, and the called function uses the
                   NRV optimization, a conforming program could see *to_p
                   change before the called function returns; see c++/19317.
                   When optimizing, the return_slot pass marks more functions
                   as safe after we have escape info.  */
                use_target = false;

so I wonder if you can modify the Ada testcase so that
CALL_EXPR_RETURN_SLOT_OPT is not set?