> Jose E. Marchesi writes:
>
>>> This patch updates the support for the BPF CO-RE builtins
>>> __builtin_preserve_access_index and __builtin_preserve_field_info,
>>> and adds support for the CO-RE builtins __builtin_btf_type_id,
>>> __builtin_preserve_type_info and __builtin_preserve_enum_value.
>>>
>>> These CO-RE relocations are now converted to __builtin_core_reloc which
>>> abstracts all of the original builtins in a polymorphic relocation
>>> specific builtin.
>>>
>>> The builtin processing is now split in 2 stages, the first (pack) is
>>> executed right after the front-end and the second (process) right before
>>> the asm output.
>>>
>>> In expand pass the __builtin_core_reloc is converted to a
>>> unspec:UNSPEC_CORE_RELOC rtx entry.
>>>
>>> The data required to process the builtin is now collected in the packing
>>> stage (after front-end), not allowing the compiler to optimize any of
>>> the relevant information required to compose the relocation when
>>> necessary.
>>> At expansion, that information is recovered and CTF/BTF is queried to
>>> construct the information that will be used in the relocation.
>>> At this point the relocation is added to specific section and the
>>> builtin is expanded to the expected default value for the builtin.
>>>
>>> In order to process __builtin_preserve_enum_value, it was necessary to
>>> hook the front-end to collect the original enum value reference.
>>> This is needed since the parser folds all the enum values to its
>>> integer_cst representation.
>>>
>>> More details can be found within the core-builtins.cc.
>>>
>>> Regtested in host x86_64-linux-gnu and target bpf-unknown-none.
>>> ---
>>> gcc/config.gcc | 4 +-
>>> gcc/config/bpf/bpf-passes.def | 20 -
>>> gcc/config/bpf/bpf-protos.h | 4 +-
>>> gcc/config/bpf/bpf.cc | 817 +---------
>>> gcc/config/bpf/bpf.md | 17 +
>>> gcc/config/bpf/core-builtins.cc | 1397 +++++++++++++++++
>>> gcc/config/bpf/core-builtins.h | 36 +
>>> gcc/config/bpf/coreout.cc | 50 +-
>>> gcc/config/bpf/coreout.h | 13 +-
>>> gcc/config/bpf/t-bpf | 6 +-
>>> gcc/doc/extend.texi | 51 +
>>> ...core-builtin-fieldinfo-const-elimination.c | 29 +
>>> 12 files changed, 1639 insertions(+), 805 deletions(-)
>>> delete mode 100644 gcc/config/bpf/bpf-passes.def
>>> create mode 100644 gcc/config/bpf/core-builtins.cc
>>> create mode 100644 gcc/config/bpf/core-builtins.h
>>> create mode 100644
>>> gcc/testsuite/gcc.target/bpf/core-builtin-fieldinfo-const-elimination.c
>>>
>>> diff --git a/gcc/config.gcc b/gcc/config.gcc
>>> index eba69a463be0..c521669e78b1 100644
>>> --- a/gcc/config.gcc
>>> +++ b/gcc/config.gcc
>>> @@ -1597,8 +1597,8 @@ bpf-*-*)
>>> use_collect2=no
>>> extra_headers="bpf-helpers.h"
>>> use_gcc_stdint=provide
>>> - extra_objs="coreout.o"
>>> - target_gtfiles="$target_gtfiles \$(srcdir)/config/bpf/coreout.cc"
>>> + extra_objs="coreout.o core-builtins.o"
>>> + target_gtfiles="$target_gtfiles \$(srcdir)/config/bpf/coreout.cc
>>> \$(srcdir)/config/bpf/core-builtins.cc"
>>> ;;
>>> cris-*-elf | cris-*-none)
>>> tm_file="elfos.h newlib-stdint.h ${tm_file}"
>>> diff --git a/gcc/config/bpf/bpf-passes.def b/gcc/config/bpf/bpf-passes.def
>>> deleted file mode 100644
>>> index deeaee988a01..000000000000
>>> --- a/gcc/config/bpf/bpf-passes.def
>>> +++ /dev/null
>>> @@ -1,20 +0,0 @@
>>> -/* Declaration of target-specific passes for eBPF.
>>> - Copyright (C) 2021-2023 Free Software Foundation, Inc.
>>> -
>>> - This file is part of GCC.
>>> -
>>> - GCC is free software; you can redistribute it and/or modify it
>>> - under the terms of the GNU General Public License as published by
>>> - the Free Software Foundation; either version 3, or (at your option)
>>> - any later version.
>>> -
>>> - GCC is distributed in the hope that it will be useful, but
>>> - WITHOUT ANY WARRANTY; without even the implied warranty of
>>> - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
>>> - General Public License for more details.
>>> -
>>> - You should have received a copy of the GNU General Public License
>>> - along with GCC; see the file COPYING3. If not see
>>> - <http://www.gnu.org/licenses/>. */
>>> -
>>> -INSERT_PASS_AFTER (pass_df_initialize_opt, 1, pass_bpf_core_attr);
>>> diff --git a/gcc/config/bpf/bpf-protos.h b/gcc/config/bpf/bpf-protos.h
>>> index b484310e8cbf..fbcf5111eb21 100644
>>> --- a/gcc/config/bpf/bpf-protos.h
>>> +++ b/gcc/config/bpf/bpf-protos.h
>>> @@ -30,7 +30,7 @@ extern void bpf_print_operand_address (FILE *, rtx);
>>> extern void bpf_expand_prologue (void);
>>> extern void bpf_expand_epilogue (void);
>>> extern void bpf_expand_cbranch (machine_mode, rtx *);
>>> -
>>> -rtl_opt_pass * make_pass_bpf_core_attr (gcc::context *);
>>> +const char *bpf_add_core_reloc (rtx *operands, const char *templ);
>>> +void bpf_process_move_operands (rtx *operands);
>>>
>>> #endif /* ! GCC_BPF_PROTOS_H */
>>> diff --git a/gcc/config/bpf/bpf.cc b/gcc/config/bpf/bpf.cc
>>> index b5b5674edbb5..101e994905d2 100644
>>> --- a/gcc/config/bpf/bpf.cc
>>> +++ b/gcc/config/bpf/bpf.cc
>>> @@ -69,10 +69,7 @@ along with GCC; see the file COPYING3. If not see
>>> #include "gimplify.h"
>>> #include "gimplify-me.h"
>>>
>>> -#include "ctfc.h"
>>> -#include "btf.h"
>>> -
>>> -#include "coreout.h"
>>> +#include "core-builtins.h"
>>>
>>> /* Per-function machine data. */
>>> struct GTY(()) machine_function
>>> @@ -174,22 +171,7 @@ static const struct attribute_spec
>>> bpf_attribute_table[] =
>>> one. */
>>> #define BPF_BUILTIN_MAX_ARGS 5
>>>
>>> -enum bpf_builtins
>>> -{
>>> - BPF_BUILTIN_UNUSED = 0,
>>> - /* Built-ins for non-generic loads and stores. */
>>> - BPF_BUILTIN_LOAD_BYTE,
>>> - BPF_BUILTIN_LOAD_HALF,
>>> - BPF_BUILTIN_LOAD_WORD,
>>> -
>>> - /* Compile Once - Run Everywhere (CO-RE) support. */
>>> - BPF_BUILTIN_PRESERVE_ACCESS_INDEX,
>>> - BPF_BUILTIN_PRESERVE_FIELD_INFO,
>>> -
>>> - BPF_BUILTIN_MAX,
>>> -};
>>> -
>>> -static GTY (()) tree bpf_builtins[(int) BPF_BUILTIN_MAX];
>>> +GTY (()) tree bpf_builtins[(int) BPF_BUILTIN_MAX];
>>>
>>> void bpf_register_coreattr_pass (void);
>>>
>>> @@ -546,6 +528,17 @@ bpf_expand_cbranch (machine_mode mode, rtx *operands)
>>> }
>>> }
>>>
>>> +/* This is used define_expand "mov<MM:mode>" to verofy if we need to
>>> replace
>>
>> Typo; verofy
>>
>>> + any of the operands. Currently this is used to replace the
>>> + __attribute__((preserve_access_index)) by the respective
>>> __builtin_core_reloc
>>> + which will at final create the relocation and respective label. */
>>> +
>>> +void
>>> +bpf_process_move_operands (rtx *operands)
>>> +{
>>> + bpf_replace_core_move_operands (operands);
>>> +}
>>
>> Is this intermediary function really necessary? Just call
>> bpf_place_core_move_operands from the expand.
> No I did it only as a placeholder for any future requirements unrelated
> to the CO-RE builtins. Will remove.
>>
>>> +(define_insn "mov_reloc_core<MM:mode>"
>>> + [(set (match_operand:MM 0 "nonimmediate_operand" "=r,q,r")
>>> + (unspec:MM [
>>> + (match_operand:MM 1 "immediate_operand" " I,I,B")
>>> + (match_operand:SI 2 "immediate_operand" " I,I,I")
>>> + ] UNSPEC_CORE_RELOC)
>>> + )]
>>> + ""
>>> + "@
>>> + *return bpf_add_core_reloc (operands, \"{mov\t%0,%1|%0 = %1}\");
>>> + *return bpf_add_core_reloc (operands, \"{st<mop>\t%0,%1|*(<smop> *)
>>> (%0) = %1}\");
>>> + *return bpf_add_core_reloc (operands, \"{lddw\t%0,%1|%0 = %1 ll}\");"
>>> + [(set_attr "type" "alu,st,alu")])
>>> +
>>
>> I am assuming that this insn only has to implement whatever situations
>> supported by valid operands and usage of the builtins in any possible
>> context, right? i.e. it doesn't have to handle all the situations that
>> "*movMODE" handles. And this is checked by the builtin implementation?
> Only the implementations of the mov that take an immediate at the second
> operand can actually be used for the builtin. This unspec is only
> expanded in case of a builtin. I presume that this limits it to these
> scenarios.
Ok, thanks for the info. I just wanted to make sure that no matter the
builtins are used in the C programs we will never get an ICE because of
lack of insns.
>
>>> +struct cr_builtins {
>>
>> Brace in first column please.
>>
>>> + /* FIXED: This wat not Ok.
>>
>> Hm? If that is fixed, do we still need that comment? :)
>>
>>> + emit_insn ( \
>>> + gen_mov_reloc_coredi (reg, \
>>> + gen_rtx_CONST_INT (Pmode, 0), \
>>> + gen_rtx_CONST_INT (Pmode, index))); \
>>
>> These backslahes... was that in a macro originally?
>>
>>> + return true;
>>> + }
>>> + }
>>> + return false;
>>> +}
>
> Thanks!
