https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103562
David Malcolm <dmalcolm at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
--- Comment #5 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Thanks for filing this bug, and for the investigation.
After a couple of hours debugging, I think I've found the discrepancy between
cc1 and libgccjit, and have a candidate fix.
When tree-inline.c:remap_gimple_stmt is called to remap the stmt:
<retval> = *ptr_2(D);
cc1 returns:
D.1989 = *ptr_2(D);
whereas libgccjit returns this (copy):
<retval> = *ptr_2(D);
Putting a breakpoint on remap_gimple_op_r and singlestepping (in both cc1 and
libgccjit, side by side) shows the discrepancy happens in
tree-inline.c:remap_gimple_op_r here:
1036 else if (auto_var_in_fn_p (*tp, fn))
For cc1:
(gdb) p auto_var_in_fn_p (*tp, fn)
$28 = true
whereas for libgccjit:
(gdb) p auto_var_in_fn_p (*tp, fn)
$19 = false
and so libgccjit erroneously skips the remapping of locals vars and labels.
This turns out to be because the RESULT_DECL has a non-NULL DECL_CONTEXT in
cc1, set here by the C frontend:
(gdb) bt
#0 finish_function (end_loc=248384) at ../../src/gcc/c/c-decl.c:10271
#1 0x00000000009db5f7 in c_parser_declaration_or_fndef (parser=0x7ffff7ffbbd0,
fndef_ok=true, static_assert_ok=true, empty_ok=true, nested=false,
start_attr_ok=true, objc_foreach_object_declaration=0x0,
omp_declare_simd_clauses=0x0, have_attrs=false, attrs=<tree 0x0>,
oacc_routine_data=0x0, fallthru_attr_p=0x0) at
../../src/gcc/c/c-parser.c:2563
#2 0x00000000009d9925 in c_parser_external_declaration (parser=0x7ffff7ffbbd0)
at ../../src/gcc/c/c-parser.c:1779
#3 0x00000000009d941d in c_parser_translation_unit (parser=0x7ffff7ffbbd0) at
../../src/gcc/c/c-parser.c:1652
#4 0x0000000000a21267 in c_parse_file () at ../../src/gcc/c/c-parser.c:23280
#5 0x0000000000abd0ab in c_common_parse_file () at
../../src/gcc/c-family/c-opts.c:1238
#6 0x00000000010cab1a in compile_file () at ../../src/gcc/toplev.c:452
#7 0x000000000093eb7a in do_compile (no_backend=false) at
../../src/gcc/toplev.c:2156
#8 toplev::main (this=0x7fffffffde1a, argc=<optimized out>, argv=<optimized
out>) at ../../src/gcc/toplev.c:2308
#9 0x000000000270339d in main (argc=24, argv=0x7fffffffdf28) at
../../src/gcc/main.c:39
(gdb) list
10266 /* Must mark the RESULT_DECL as being in this function. */
10267
10268 if (DECL_RESULT (fndecl) && DECL_RESULT (fndecl) != error_mark_node)
10269 DECL_CONTEXT (DECL_RESULT (fndecl)) = fndecl;
whereas the RESULT_DECL has NULL for its DECL_CONTEXT.
On trying this patch:
--- a/gcc/jit/jit-playback.c
+++ b/gcc/jit/jit-playback.c
@@ -473,6 +473,7 @@ new_function (location *loc,
DECL_ARTIFICIAL (resdecl) = 1;
DECL_IGNORED_P (resdecl) = 1;
DECL_RESULT (fndecl) = resdecl;
+ DECL_CONTEXT (resdecl) = fndecl;
if (builtin_id)
{
then remap_gimple_stmt in libgccjit correctly remaps the stmt to:
(gdb) call debug ($21)
D.88 = *ptr_2(D);
and I correctly get this output from the libgccjit testcase:
get_a(&s) is 1
i.e. the above patch seems to fix it.
I'm running some more thorough tests.
