On Wed, 18 Aug 2021, Qing Zhao wrote:
>
>
> > On Aug 18, 2021, at 2:15 AM, Richard Biener <rguent...@suse.de> wrote:
> >
> > On Tue, 17 Aug 2021, Qing Zhao wrote:
> >
> >>
> >>
> >>> On Aug 17, 2021, at 9:50 AM, Qing Zhao via Gcc-patches
> >>> <gcc-patches@gcc.gnu.org> wrote:
> >>>
> >>>
> >>>
> >>>> On Aug 17, 2021, at 3:29 AM, Richard Biener <rguent...@suse.de> wrote:
> >>>>
> >>>> On Mon, 16 Aug 2021, Qing Zhao wrote:
> >>>>
> >>>>> My current code for expand_DEFERRED_INIT is like the following, could
> >>>>> you check and see whether there is any issue for it:
> >>>>>
> >>>>> #define INIT_PATTERN_VALUE 0xFE
> >>>>> static void
> >>>>> expand_DEFERRED_INIT (internal_fn, gcall *stmt)
> >>>>> {
> >>>>> tree lhs = gimple_call_lhs (stmt);
> >>>>> tree var_size = gimple_call_arg (stmt, 0);
> >>>>> enum auto_init_type init_type
> >>>>> = (enum auto_init_type) TREE_INT_CST_LOW (gimple_call_arg (stmt, 1));
> >>>>> bool is_vla = (bool) TREE_INT_CST_LOW (gimple_call_arg (stmt, 2));
> >>>>>
> >>>>> tree var_type = TREE_TYPE (lhs);
> >>>>> gcc_assert (init_type > AUTO_INIT_UNINITIALIZED);
> >>>>>
> >>>>> if (is_vla || (!use_register_for_decl (lhs)))
> >>>>> {
> >>>>> if (TREE_CODE (lhs) == SSA_NAME)
> >>>>> lhs = SSA_NAME_VAR (lhs);
> >>>>
> >>>> this should not be necessary (in fact you shouldn't see a SSA_NAME
> >>>> here, if you do then using SSA_NAME_VAR is wrong)
> >>> You mean during RTL expansion phase, all SSA_NAMEs are gone already?
> >>
> >> Actually, the lhs could be SSA_NAME here,
> >>
> >> Breakpoint 1, expand_DEFERRED_INIT (stmt=0x7fffe96ae348) at
> >> ../../latest-gcc/gcc/internal-fn.c:3021
> >> 3021 mark_addressable (lhs);
> >> (gdb) call debug_tree(lhs)
> >> <ssa_name 0x7fffe9584e58
> >> type <real_type 0x7fffe959b2a0 float sizes-gimplified SF
> >> size <integer_cst 0x7fffe9579f48 constant 32>
> >> unit-size <integer_cst 0x7fffe9579f60 constant 4>
> >> align:32 warn_if_not_align:0 symtab:0 alias-set 2 canonical-type
> >> 0x7fffe959b2a0 precision:32
> >> pointer_to_this <pointer_type 0x7fffe959b7e0>>
> >> visited var <var_decl 0x7ffff7ff7bd0 temp1>
> >> def_stmt temp1_5 = .DEFERRED_INIT (4, 2, 0, &"temp1"[0]);
> >> version:5>
> >>
> >> when I deleted:
> >>
> >> if (TREE_CODE (lhs) == SSA_NAME
> >> lhs = SSA_NAME_VAR (lhs);
> >
> > but then using SSA_NAME_VAR is broken. I suspect use_register_for_decl
> > isn't the correct thing to look at. I think we need to look at what
> > the LHS expanded to if it is a SSA_VAR_P (that includes SSA names
> > but also plain DECLs but not what we get from VLAs where we'd see
> > *ptr). So sth like
> >
> > bool reg_lhs;
> > if (SSA_VAR_P (lhs))
> > {
> > rtx tem = expand_expr (lhs, NULL_RTX, VOIDmode, EXPAND_WRITE);
> > reg_lhs = !MEM_P (tem);
> > /* If not MEM_P reg_lhs should be REG_P or SUBREG_P (but maybe
> > also CONCAT or lowpart...?) */
> > }
> > else
> > {
> > gcc_assert (is_vla);
> > reg_lhs = false;
> > }
> >
> > if (!reg_lhs)
> > memset path
> > else
> > expand_assignment path
>
> After making the following change:
>
> + bool reg_lhs = true;
>
> tree var_type = TREE_TYPE (lhs);
> gcc_assert (init_type > AUTO_INIT_UNINITIALIZED);
>
> - if (is_vla || (!use_register_for_decl (lhs)))
> + if (SSA_VAR_P (lhs))
> + {
> + rtx tem = expand_expr (lhs, NULL_RTX, VOIDmode, EXPAND_WRITE);
> + reg_lhs = !MEM_P (tem);
> + }
> + else
> + {
> + gcc_assert (is_vla);
> + reg_lhs = false;
> + }
> +
> + if (!reg_lhs)
> {
>
> I got exactly the same internal error that failed at expr.c:
>
> 8436 /* We must have made progress. */
> 8437 gcc_assert (inner != exp);
>
>
> Looks like for the following code:
>
> 3026 if (!reg_lhs)
> 3027 {
> 3028 /* If this is a VLA or the variable is not in register,
> 3029 expand to a memset to initialize it. */
> 3030 mark_addressable (lhs);
> 3031 tree var_addr = build_fold_addr_expr (lhs);
> 3032
> 3033 tree value = (init_type == AUTO_INIT_PATTERN) ?
> 3034 build_int_cst (integer_type_node,
> 3035 INIT_PATTERN_VALUE) :
> 3036 integer_zero_node;
> 3037 tree m_call = build_call_expr (builtin_decl_implicit
> (BUILT_IN_MEMSET),
> 3038 3, var_addr, value, var_size);
> 3039 /* Expand this memset call. */
> 3040 expand_builtin_memset (m_call, NULL_RTX, TYPE_MODE (var_type));
> 3041 }
>
> At line 3030, “lhs” could be a SSA_NAME.
>
> My questions are:
>
> 1. Could the routine “mark_addressable” and “build_fold_addr_expr” be applied
> on SSA_NAME?
No.
> 2. Could the routine “expand_builtin_memset” be applied on the memset call
> whose “DEST” is
> an address expression on SSA_NAME?
No.
> 3. Within “expand_DEFERRED_INIT”, can I call “expand_builtin_memset” to
> expand .DEFERRED_INIT?
Well, not with "invalid" GENERIC I fear (address of a SSA name).
> I suspect that one of the above 3 might be the issue, but not sure which one?
All of the above ;) So while reg_lhs is now precise as to how the
variable will end up (the SSA name will end up as a stack variable in this
case, for whatever reason), expansion via memcpy only works when
working on the RTL representation. The usual "workaround" (ugh)
is to use make_tree (), so in the !reg_lhs path you'd do
/* Get a new GENERIC representation for the RTL. That's necesary
in case LHS is an SSA name. */
lhs = make_tree (TREE_TYPE (lhs), tem);
alternatively you could maybe do
if (DECL_P (lhs))
{
+ rtx tem = expand_expr (lhs, NULL_RTX, VOIDmode, EXPAND_WRITE);
+ reg_lhs = !MEM_P (tem);
}
else if (TREE_CODE (lhs) == SSA_NAME)
reg_lhs = true;
else
reg_lhs = false;
thus treat SSA names as register storage always (even if it will end
up on the stack).
Richard.
> Thanks a lot.
>
> Qing
>
>
>
> > bool reg_lhs;
> > if (SSA_VAR_P (lhs))
> > {
> > rtx tem = expand_expr (lhs, NULL_RTX, VOIDmode, EXPAND_WRITE);
> > reg_lhs = !MEM_P (tem);
> > /* If not MEM_P reg_lhs should be REG_P or SUBREG_P (but maybe
> > also CONCAT or lowpart...?) */
> > }
> > else
> > {
> > gcc_assert (is_vla);
> > reg_lhs = false;
> > }
>
>
> >
> >> Many testing cases failed with internal compiler error:
> >>
> >> /home/opc/Work/GCC/latest-gcc/gcc/testsuite/c-c++-common/auto-init-3.c:9:9:
> >> internal compiler error: in expand_expr_addr_expr_1, at expr.c:8437
> >> 0xe237aa expand_expr_addr_expr_1
> >> ../../latest-gcc/gcc/expr.c:8437
> >> 0xe24059 expand_expr_addr_expr
> >> ../../latest-gcc/gcc/expr.c:8525
> >> 0xe32b56 expand_expr_real_1(tree_node*, rtx_def*, machine_mode,
> >> expand_modifier, rtx_def**, bool)
> >> ../../latest-gcc/gcc/expr.c:11741
> >> 0xe2da52 expand_expr_real_1(tree_node*, rtx_def*, machine_mode,
> >> expand_modifier, rtx_def**, bool)
> >> ../../latest-gcc/gcc/expr.c:10777
> >> 0xe24706 expand_expr_real(tree_node*, rtx_def*, machine_mode,
> >> expand_modifier, rtx_def**, bool)
> >> ../../latest-gcc/gcc/expr.c:8713
> >> 0xc13f15 expand_expr
> >> ../../latest-gcc/gcc/expr.h:301
> >> 0xc17acb get_memory_rtx
> >> ../../latest-gcc/gcc/builtins.c:1370
> >> 0xc2223d expand_builtin_memset_args
> >> ../../latest-gcc/gcc/builtins.c:4102
> >> 0xc21a20 expand_builtin_memset(tree_node*, rtx_def*, machine_mode)
> >> ../../latest-gcc/gcc/builtins.c:3886
> >> 0xfb5c85 expand_DEFERRED_INIT
> >> ../../latest-gcc/gcc/internal-fn.c:3031
> >>
> >>
> >> So, did I do anything wrong?
> >>
> >> Qing
> >
> > --
> > Richard Biener <rguent...@suse.de>
> > SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
> > Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
