Help debugging middle-end crash (SSA inlining)

[Janne Blomqvist <blomqvist dot janne at gmail dot com>]

Hi,

I'm working on a patch to change the type that GFortran uses for
string lengths from a C int to a C size_t. I'm at a point where it
does regtest successfully, with the exception of
gfortran.dg/char_result_8.f90 with -O1 where it ICE's. Unfortunately
I'm a bit stuck here, and haven't been able to figure out what causes
the error.

The latest version of the patch is attached to PR 78534.

It does work with -O0, -O2, -O3, -Og, -Ofast as well as "-O1
-fno-inline-functions-called-once". Which suggests that the problem is
in the inliner (why it doesn't trigger with higher optimization level,
I don't know).

The backtrace of the crash is

char_result_8.f90:14:0:

   call indirect (100)

internal compiler error: Segmentation fault
0xcda61e crash_signal
        ../../trunk-git/gcc/toplev.c:333
0xfa99e4 make_ssa_name_fn(function*, tree_node*, gimple*, unsigned int)
        ../../trunk-git/gcc/tree-ssanames.c:265
0xd7e26a make_ssa_name
        ../../trunk-git/gcc/tree-ssanames.h:113
0xd7e26a remap_ssa_name
        ../../trunk-git/gcc/tree-inline.c:238
0xd84ee2 copy_tree_body_r(tree_node**, int*, void*)
        ../../trunk-git/gcc/tree-inline.c:1082
0x108c7a4 walk_tree_1(tree_node**, tree_node* (*)(tree_node**, int*,
void*), void*, hash_set<tree_node*, default_hash_traits<tree_node*>
>*, tree_node* (*)(tree_node**, int*, tree_node* (*)(tree_node**,
int*, void*), void*, hash_set<tree_node*,
default_hash_traits<tree_node*> >*))
        ../../trunk-git/gcc/tree.c:11795
0x108da12 walk_tree_1(tree_node**, tree_node* (*)(tree_node**, int*,
void*), void*, hash_set<tree_node*, default_hash_traits<tree_node*>
>*, tree_node* (*)(tree_node**, int*, tree_node* (*)(tree_node**,
int*, void*), void*, hash_set<tree_node*,
default_hash_traits<tree_node*> >*))
        ../../trunk-git/gcc/tree.c:12112
0xd7c41a remap_type_1
        ../../trunk-git/gcc/tree-inline.c:493
0xd7d2cc remap_type(tree_node*, copy_body_data*)
        ../../trunk-git/gcc/tree-inline.c:593
0xd7cbc5 remap_type_1
        ../../trunk-git/gcc/tree-inline.c:523
0xd7d2cc remap_type(tree_node*, copy_body_data*)
        ../../trunk-git/gcc/tree-inline.c:593
0xd7b721 remap_type_1
        ../../trunk-git/gcc/tree-inline.c:418
0xd7d2cc remap_type(tree_node*, copy_body_data*)
        ../../trunk-git/gcc/tree-inline.c:593
0xd7b1c9 remap_decl(tree_node*, copy_body_data*)
        ../../trunk-git/gcc/tree-inline.c:370
0xd7d849 add_local_variables
        ../../trunk-git/gcc/tree-inline.c:4321
0xd8973a expand_call_inline
        ../../trunk-git/gcc/tree-inline.c:4733
0xd8a4b8 gimple_expand_calls_inline
        ../../trunk-git/gcc/tree-inline.c:4896
0xd8a6cf optimize_inline_calls(tree_node*)
        ../../trunk-git/gcc/tree-inline.c:5036
0x164c339 inline_transform(cgraph_node*)
        ../../trunk-git/gcc/ipa-inline-transform.c:655
0xbe121c execute_one_ipa_transform_pass
        ../../trunk-git/gcc/passes.c:2206


Where it crashes is the assertion "VAR_P (var)", because var is a null
pointer. Running this via gdb I have found that in this case "var" is
the type node for one of the variables that it apparently is copying
from the callee into the caller during the inlining.

So I guess I'm asking how can it happen that the type node of a
variable disappears?

I have compared the -fdump-tree original dumps of trunk and
trunk+patch, and they look perfectly Ok; except for character length
types being different and a few typecasts in some appropriate places,
they are identical.

Can anybody offer some clues?

TIA,

-- 
Janne Blomqvist