https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66470
Bug ID: 66470
Summary: [4.8/4.9/5/6 Regression] TLS ICE due to
ix86_split_long_move
Product: gcc
Version: 5.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: jakub at gcc dot gnu.org
Target Milestone: ---
extern __thread unsigned long long a[10];
unsigned long long foo (int b) { return a[b]; }
or
extern __thread struct S { int a, b; } a[10];
struct S foo (int b) { return a[b]; }
ICE on x86_64-linux/i686-linux with -m32, all optimization levels. This worked
in GCC 3.3.6.
The bug is in ix86_split_long_move, when trying to split:
(insn 7 15 13 2 (set (reg:DI 0 ax [92])
(mem:DI (plus:SI (plus:SI (mult:SI (reg/v:SI 1 dx [orig:89 b ] [89])
(const_int 8 [0x8]))
(unspec:SI [
(const_int 0 [0])
] UNSPEC_TP))
(reg:SI 0 ax [91])) [1 a S8 A64])) rh1212265.i:2 85
{*movdi_internal}
(nil))
which, while offsettable, has collisions == 2 (the MEM uses both dx and ax in
the addressing and loads the ax:dx pair). The splitter assumes it can just use
a lea, but lea can't support %gs: (UNSPEC_TP). So, either it has to load from
%gs:0 first, then do lea, or better yet just move UNSPEC_TP part to the
individual memory loads.
