[gcc r12-9501] c++, coroutines: Stabilize names of promoted slot vars [PR101118].

[Iain D Sandoe <iains@gcc.gnu.org>]

https://gcc.gnu.org/g:b7e75cdb218f25708b8b1aa3f4b138d88187491f

commit r12-9501-gb7e75cdb218f25708b8b1aa3f4b138d88187491f
Author: Iain Sandoe <iain@sandoe.co.uk>
Date:   Thu Mar 30 13:14:23 2023 +0530

    c++,coroutines: Stabilize names of promoted slot vars [PR101118].
    
    When we need to 'promote' a value (i.e. store it in the coroutine frame) it
    is given a frame entry name.  This was based on the DECL_UID for slot vars.
    However, when LTO is used, the names from multiple TUs become visible at the
    same time, and the DECL_UIDs usually differ between units.  This leads to a
    "ODR mismatch" warning for the frame type.
    
    The fix here is to use the current promoted temporaries count to produce
    the name, this is stable between TUs and computed per coroutine.
    
    Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
    
            PR c++/101118
    
    gcc/cp/ChangeLog:
    
            * coroutines.cc (flatten_await_stmt): Use the current count of
            promoted temporaries to build a unique name for the frame entries.
    
    (cherry picked from commit fc4cde2e6aa4d6ebdf7f70b7b4359fb59a1915ae)

Diff:
---
 gcc/cp/coroutines.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
index 71a22b5ad90..03ba3f6aa26 100644
--- a/gcc/cp/coroutines.cc
+++ b/gcc/cp/coroutines.cc
@@ -2883,7 +2883,7 @@ flatten_await_stmt (var_nest_node *n, hash_set<tree> *promoted,
 	  tree init = t;
 	  temps_used->add (init);
 	  tree var_type = TREE_TYPE (init);
-	  char *buf = xasprintf ("D.%d", DECL_UID (TREE_OPERAND (init, 0)));
+	  char *buf = xasprintf ("T%03u", (unsigned) temps_used->elements ());
 	  tree var = build_lang_decl (VAR_DECL, get_identifier (buf), var_type);
 	  DECL_ARTIFICIAL (var) = true;
 	  free (buf);