https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119835
Thomas Schwinge <tschwinge at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Assignee|unassigned at gcc dot gnu.org |tschwinge at gcc dot
gnu.org
Status|UNCONFIRMED |ASSIGNED
CC| |rguenth at gcc dot gnu.org
Keywords| |openacc
Last reconfirmed| |2025-05-20
--- Comment #1 from Thomas Schwinge <tschwinge at gcc dot gnu.org> ---
So, this issue can generally be triggered with code that return a struct. For
example, offload-compiling ('-fopenacc' or '-fopenmp')
'libgomp.oacc-c-c++-common/abi-struct-1.c' with '-O1 -fno-inline', we get for
'rempty' (but also 'rschar', for example):
Breakpoint 2, (anonymous namespace)::pass_nrv::execute (this=0x24e0670,
fun=0x7ffff790add0) at ../../source-gcc/gcc/tree-nrv.cc:137
137 {
(gdb) n
138 tree result = DECL_RESULT (current_function_decl);
[...]
173 if (greturn *return_stmt = dyn_cast <greturn *> (stmt))
(gdb) n
178 ret_val = gimple_return_retval (return_stmt);
(gdb) n
179 if (ret_val)
(gdb) n
180 gcc_assert (ret_val == result);
(gdb) print result
$4 = (tree) 0x7ffff77fb300
(gdb) call debug_tree(result)
<result_decl 0x7ffff77fb300 D.1834
type <record_type 0x7ffff77b0b28 empty BLK
size <integer_cst 0x7ffff76eb4e0 constant 0>
unit-size <integer_cst 0x7ffff76eb498 constant 0>
align:8 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7ffff77b0a80>
ignored BLK
source-gcc/libgomp/testsuite/libgomp.oacc-c-c++-common/abi-struct-1.c:19:14
size <integer_cst 0x7ffff76eb4e0 0> unit-size <integer_cst 0x7ffff76eb498 0>
align:8 warn_if_not_align:0 context <function_decl 0x7ffff77e0000
rempty>>
(gdb) print ret_val
$5 = (tree) 0x7ffff77f4a18
(gdb) call debug_tree(ret_val)
<var_decl 0x7ffff77f4a18 D.1835
type <record_type 0x7ffff77b0b28 empty BLK
size <integer_cst 0x7ffff76eb4e0 constant 0>
unit-size <integer_cst 0x7ffff76eb498 constant 0>
align:8 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7ffff77b0a80>
ignored BLK
source-gcc/libgomp/testsuite/libgomp.oacc-c-c++-common/abi-struct-1.c:21:11
size <integer_cst 0x7ffff76eb4e0 0> unit-size <integer_cst 0x7ffff76eb498 0>
align:8 warn_if_not_align:0 context <function_decl 0x7ffff77e0000
rempty>>
..., so there is indeed a disconnect between 'DECL_RESULT' and
'gimple_return_retval'.
The source code says: "In a function with an aggregate return value, the
gimplifier has changed all non-empty RETURN_EXPRs to return the RESULT_DECL.",
so I suppose the issue is that for offloading we're rewriting some DECLs, but
are missing to update something?
If I disable this local check (the 'ret_val' variable isn't used for anything
other than the 'assert'), the ICE goes away -- and the pass doesn't do any
transformations (for 'libgomp.oacc-c-c++-common/abi-struct-1.c'), so not sure
whether that finding implies anything useful.
