> -----原始邮件-----
> 发件人: "Palmer Dabbelt" <pal...@rivosinc.com>
> 发送时间: 2021-12-31 00:59:08 (星期五)
> 收件人: jeffreya...@gmail.com
> 抄送: gcc-patches@gcc.gnu.org, jia...@iscas.ac.cn, gcc-patches@gcc.gnu.org,
indu.bha...@oracle.com, kito.ch...@sifive.com, yul...@nj.iscas.ac.cn,
si...@isrc.iscas.ac.cn, shi...@iscas.ac.cn
> 主题: Re: [PATCH] Testsuite: Add btf-dataset option for RISC-V.
>
> On Thu, 30 Dec 2021 08:28:34 PST (-0800), gcc-patches@gcc.gnu.org wrote:
> >
> >
> > On 12/29/2021 8:02 PM, jiawei wrote:
> >> Add -msmall-data-limit option to put global and static data into
right
> >> section and generate 'btt_info' on RISC-V target.
> >>
> >> BTF (BPF Type Format) is the metadata format which encodes the
debug info related to BPF program/map, more details on:
> >>
https://www.kernel.org/doc/html/latest/bpf/index.html#bpf-type-format-btf
> >>
> >> gcc/testsuite/ChangeLog:
> >>
> >> * gcc.dg/debug/btf/btf-datasec-1.c: Add riscv target
support.
> > Is the goal here to get the variable "d" out of the small data section
> > and into the standard data section? It's not clear from your
description .
> >
> > Neither an ACK nor a NAK at this point. I need to understand
better
> > what you're trying to accomplish.
Thanks for your mentions, the testcase said it expect 3 DATASEC records: one
for each of .data, .rodata and .bss.
If we only use /* { dg-options "-O0 -gbtf -dA" } */ as default compile option
on riscv target like:
```````````````````
$ riscv64-unknown-elf-gcc -S -O0 -gbtf -dA btf-datasec-1.c
```````````````````
the variable in section will be throw into .sdata, .sbss, .srodata and don't
fit the check require, and I add the additional option '-msmall-data-limit' to
fix it, to get a correct .section part, we need to limit the
'-msmall-data-limit' less than the smallest variable 'int a' size define as 4
byte, then it will be send into section .bss.
```````````````````
$ riscv64-unknown-elf-gcc -S -O0 -gbtf -dA btf-datasec-1.c -o btf-datasec-1.s
.Ltext0:
.cfi_sections .debug_frame
.file 0 "/root/test" "btf-datasec-1.c"
.globl a
.section .sbss,"aw",@nobits
.align 2
.type a, @object
.size a, 4
$ riscv64-unknown-elf-gcc -S -O0 -gbtf -dA -msmall-data-limit=2 btf-datasec-1.c
-o btf-datasec-2.s
.Ltext0:
.cfi_sections .debug_frame
.file 0 "/root/test" "btf-datasec-1.c"
.globl a
.bss
.align 2
.type a, @object
.size a, 4
```````````````````
It is seem on other variable, and when all section set right, all check in the
testcase can pass on riscv.
```````````````````
$ diff btf-datasec-1.s btf-datasec-2.s
> .bss
144c163
< .section .srodata,"a"
---
> .section .rodata
151c170
< .section .sdata,"aw"
---
> .data
158c177
< .section .srodata
---
> .section .rodata
```````````````````
>
> IIUC that's what this is doing, though the commit message isn't clear at
> all. That saind, it might be better to do something like
Sorry for the unclear commit, I explained the idea in this mail, should I
resend the patch?
>
> diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf-datasec-1.c
b/gcc/testsuite/gcc.dg/debug/btf/btf-datasec-1.c
> index dbb236bbda1..c0ad77d40aa 100644
> --- a/gcc/testsuite/gcc.dg/debug/btf/btf-datasec-1.c
> +++ b/gcc/testsuite/gcc.dg/debug/btf/btf-datasec-1.c
> @@ -22,9 +22,9 @@
> /* { dg-final { scan-assembler-times "0\[\t \]+\[^\n\]*bts_offset" 7
} } */
>
> /* Check that strings for each DATASEC have been added to the BTF
string table. */
> -/* { dg-final { scan-assembler-times "ascii \".data.0\"\[\t
\]+\[^\n\]*btf_aux_string" 1 } } */
> -/* { dg-final { scan-assembler-times "ascii \".rodata.0\"\[\t
\]+\[^\n\]*btf_aux_string" 1 } } */
> -/* { dg-final { scan-assembler-times "ascii \".bss.0\"\[\t
\]+\[^\n\]*btf_aux_string" 1 } } */
> +/* { dg-final { scan-assembler-times "ascii \".[s]?data.0\"\[\t
\]+\[^\n\]*btf_aux_string" 1 } } */
> +/* { dg-final { scan-assembler-times "ascii \".[s]?rodata.0\"\[\t
\]+\[^\n\]*btf_aux_string" 1 } } */
> +/* { dg-final { scan-assembler-times "ascii \".[s]?bss.0\"\[\t
\]+\[^\n\]*btf_aux_string" 1 } } */
>
> int a;
> long long b;
>
> as whether specific symbols end up in .data or .sdata is really just an
> optimization and either should be sufficiently correct.
>
Yes, I think you are quite right, this is a question that the symbol goes
different section after optimization.
> IIRC some targets have other flavors of these, PPC's .sdata2 comes to
> mind. Not sure if we'd need that to drop their -msdata=none flag.
I'm not familiar with other target, maybe there are some error parts with my
understanding, Thanks at all!
</pal...@rivosinc.com>
