https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64111
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot
gnu.org
Target Milestone|--- |5.0
--- Comment #17 from Richard Biener <rguenth at gcc dot gnu.org> ---
<view_convert_expr 0x7ffff6836660
type <vector_type 0x10001e8608
type <integer_type 0x10001dedc8 long long int DI
size <integer_cst 0x100000eb00 constant 64>
unit size <integer_cst 0x100000eb20 constant 8>
align 64 symtab 0 alias set -1 canonical type 0x10001dedc8
precision 64 min <integer_cst 0x1000010b40 -9223372036854775808> max
<integer_cst 0x1000010b60 9223372036854775807>
pointer_to_this <pointer_type 0x10001e5a10>>
V4DI
size <integer_cst 0x1000010d40 constant 256>
unit size <integer_cst 0x1000010d80 constant 32>
align 256 symtab 0 alias set -1 canonical type 0x10001e86b0 nunits 4
pointer_to_this <pointer_type 0x10001e8758>>
arg 0 <ssa_name 0x7ffff68830d8
type <vector_type 0x7ffff686a000 type <integer_type 0x10001ded20 long
unsigned int>
unsigned V4DI
size <integer_cst 0x7ffff6851de0 constant 256> unit size
<integer_cst 0x1000010d80 32>
align 256 symtab 0 alias set 6 canonical type 0x7ffff686a000 nunits
4
pointer_to_this <pointer_type 0x7ffff6870690>>
var <var_decl 0x7ffff68825f0 vect_var_.22>def_stmt vect_var_.22_70 =
MEM[(struct QAbstractAnimationTimer * const &)vect_ppretmp.18_68];
version 70>>
It looks like PCH causes integer constant sharing to break down.
(gdb) p debug_tree ((tree)0x7ffff6851de0)
<integer_cst 0x7ffff6851de0 type <integer_type 0x10001de690 bitsizetype>
constant 256>
$2 = void
(gdb) p debug_tree ((tree)0x1000010d40)
<integer_cst 0x1000010d40 type <integer_type 0x10001de690 bitsizetype>
constant 256>
the constant is above the integer share limit thus it only gets shared
via the int_cst_hash_table hashtable which is collectible:
static GTY ((if_marked ("ggc_marked_p"), param_is (union tree_node)))
htab_t int_cst_hash_table;
but we are supposed to save that into the PCH file and restore it.
tree-cfg.c relies on this:
else if (TREE_CODE (op) == SSA_NAME
&& TYPE_SIZE (TREE_TYPE (expr)) != TYPE_SIZE (TREE_TYPE
(op)))
{
error ("conversion of register to a different size");
though from a quick grep it doesn't seem to be the only one doing so:
fold-const.c: return ((TYPE_SIZE (TREE_TYPE (arg0)) == TYPE_SIZE (TREE_TYPE
(arg1))
tree-inline.c: gcc_checking_assert (TYPE_SIZE (type) == TYPE_SIZE
(TYPE_MAIN_VARIANT (type)));
tree-inline.c: gcc_checking_assert (TYPE_SIZE_UNIT (type) ==
TYPE_SIZE_UNIT (TYPE_MAIN_VARIANT (type)));
tree-inline.c: || TYPE_SIZE (TREE_TYPE (p)) == TYPE_SIZE (TREE_TYPE
(value)))
tree-inline.c: else if (TYPE_SIZE (req_type) == TYPE_SIZE
(TREE_TYPE (replace_info->new_tree)))
Ah, the issue might be that we have (on the 4.8 branch):
/* Return the hash code code X, an INTEGER_CST. */
static hashval_t
int_cst_hash_hash (const void *x)
{
const_tree const t = (const_tree) x;
return (TREE_INT_CST_HIGH (t) ^ TREE_INT_CST_LOW (t)
^ htab_hash_pointer (TREE_TYPE (t)));
}
thus we hash in the pointer value ... (oops). Similar on trunk:
/* Return the hash code code X, an INTEGER_CST. */
hashval_t
int_cst_hasher::hash (tree x)
{
const_tree const t = x;
hashval_t code = htab_hash_pointer (TREE_TYPE (t));
int i;
for (i = 0; i < TREE_INT_CST_NUNITS (t); i++)
code ^= TREE_INT_CST_ELT (t, i);
return code;
}
I'm quite sure that doesn't survive pointer-swizzling with PCH.
I suggest to use a better hash than a simple XOR and rather than hashing
in TREE_TYPE hash in TYPE_UID.
