https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115097
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Testcase for the inliner issue:
struct A { int a; short b; };
A test(A& a) { return a; }
A test1(A& a) { return test(a); }
where the issue is that test() doesn't use DECL_RESULT for its return and thus
declare_return_variable setting up DECL_RESULT mapped to the call LHS doesn't
help.
And the reason why we don't use DECL_RESULT is that we have
<return_expr 0x7ffff6bb0d40
type <void_type 0x7ffff6a30f18 void VOID
align:8 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7ffff6a30f18
pointer_to_this <pointer_type 0x7ffff6a37000>>
side-effects
arg:0 <init_expr 0x7ffff6bb7fc8
type <record_type 0x7ffff6bbdbd0 A cxx-odr-p type_5 DI
size <integer_cst 0x7ffff6a29240 constant 64>
unit-size <integer_cst 0x7ffff6a29258 constant 8>
align:32 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7ffff6bbdbd0 fields <function_decl 0x7ffff6bd5000 __dt > context
<translation_unit_decl 0x7ffff6a18168 t2.ii>
full-name "struct A"
X() X(constX&) this=(X&) n_parents=0 use_template=0
interface-unknown
pointer_to_this <pointer_type 0x7ffff6bbde70> reference_to_this
<reference_type 0x7ffff6bbdd20> chain <type_decl 0x7ffff6a3ebe0 A>>
side-effects
arg:0 <result_decl 0x7ffff6bd1000 D.2798 type <record_type
0x7ffff6bbdbd0 A>
ignored DI t2.ii:2:1 size <integer_cst 0x7ffff6a29240 64> unit-size
<integer_cst 0x7ffff6a29258 8>
align:32 warn_if_not_align:0 context <function_decl 0x7ffff6bc0500
test>>
arg:1 <target_expr 0x7ffff6a09700 type <record_type 0x7ffff6bbdbd0 A>
side-effects tree_3 arg:0 <var_decl 0x7ffff6a19cf0 D.2823>
...
and gimplification changes the RESULT_DECL return because
/* If aggregate_value_p is true, then we can return the bare RESULT_DECL.
Recall that aggregate_value_p is FALSE for any aggregate type that is
returned in registers. If we're returning values in registers, then
we don't want to extend the lifetime of the RESULT_DECL, particularly
across another call. In addition, for those aggregates for which
hard_function_value generates a PARALLEL, we'll die during normal
expansion of structure assignments; there's special code in expand_return
to handle this case that does not exist in expand_expr. */
but the code does something else, using a new temporary register
(here !aggregate_value_p). The following fixes that.
diff --git a/gcc/gimplify.cc b/gcc/gimplify.cc
index b0ed58ed0f9..e4cf5438e39 100644
--- a/gcc/gimplify.cc
+++ b/gcc/gimplify.cc
@@ -1873,7 +1873,8 @@ gimplify_return_expr (tree stmt, gimple_seq *pre_p)
to handle this case that does not exist in expand_expr. */
if (!result_decl)
result = NULL_TREE;
- else if (aggregate_value_p (result_decl, TREE_TYPE (current_function_decl)))
+ else if (aggregate_value_p (result_decl, TREE_TYPE (current_function_decl))
+ || !is_gimple_reg_type (TREE_TYPE (result_decl)))
{
if (!poly_int_tree_p (DECL_SIZE (result_decl)))
{
