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From: Nelson Chu <nelson@rivosinc.com>
To: lifang_xia@linux.alibaba.com
Cc: binutils@sourceware.org, gkm@rivosinc.com, palmer@rivosinc.com
Subject: Re: [PATCH v2] RISC-V: Optimize relax of GP/call with max_alignment.
Date: Tue, 22 Nov 2022 18:19:00 +0800	[thread overview]
Message-ID: <CAPpQWtDQe-Frq+wZFuOUFzSyh2FCjbMagYdtbm0PqOJJHRoX1Q@mail.gmail.com> (raw)
In-Reply-To: <20221027031915.4013-1-lifang_xia@linux.alibaba.com>

On Thu, Oct 27, 2022 at 11:19 AM <lifang_xia@linux.alibaba.com> wrote:
>
> From: Lifang Xia <lifang_xia@linux.alibaba.com>
>
> The max_alignment defined out of [gp-2K, gp+2k), the max_alignment
> shouldn't affect the relax of gp.
> If the symbol is in [gp-2K, gp+2k), the max_alignment would be
> replaced with the max_alignment of the section in [gp-2k, gp+2k).
>
> Likewise, the max_alignment defined out of [call-1M, call+1M),
> the max_alignment shouldn't affect the relax of call.
> If the symbol is in [call-1M, call+1M), the max_alignment would be
> replaced with the max_alignment of the section in [call-1M, call+1M).

I'm thinking that - If it is safe enough to decide which output
section alignments should be considered in the range of gp/pc, but the
target symbols or the gp are ABS symbols.  If one of them is ABS, then
that means the output sections in the range of pc/gp may be different
in the different relax rounds.  So maybe we should,
1. make sure the target symbol and gp/pc are not ABS symbols, they
should belong to a section.
2. consider the maximum output section alignment between the output
sections of the target symbol and gp/pc.
3. Otherwise, consider all output section alignments as usual.

Thanks
Nelson

> bfd/
>         * elfnn-riscv.c (_bfd_riscv_get_max_alignment_in_jtype): New.
>         (_bfd_riscv_relax_call): The max_alignment of sections is from
>         [base-1M, base+1M).
>         (_bfd_riscv_get_max_alignment_in_itype): New.
>         (_bfd_riscv_relax_lui): The max_alignment of sections is from
>         [gp-2K, gp+2K).
>         (_bfd_riscv_relax_pc): Likewise.
> ld/
>         * ld/testsuite/ld-riscv-elf/relax-max-align-call.*: New tests.
>         * ld/testsuite/ld-riscv-elf/relax-max-align-gp.*: New tests.
> ---
>  bfd/elfnn-riscv.c                             | 67 +++++++++++++++++++
>  ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp    |  2 +
>  .../ld-riscv-elf/relax-max-align-call.d       | 18 +++++
>  .../ld-riscv-elf/relax-max-align-call.ld      | 22 ++++++
>  .../ld-riscv-elf/relax-max-align-call.s       | 23 +++++++
>  .../ld-riscv-elf/relax-max-align-gp.d         | 46 +++++++++++++
>  .../ld-riscv-elf/relax-max-align-gp.s         | 29 ++++++++
>  7 files changed, 207 insertions(+)
>  create mode 100644 ld/testsuite/ld-riscv-elf/relax-max-align-call.d
>  create mode 100644 ld/testsuite/ld-riscv-elf/relax-max-align-call.ld
>  create mode 100644 ld/testsuite/ld-riscv-elf/relax-max-align-call.s
>  create mode 100644 ld/testsuite/ld-riscv-elf/relax-max-align-gp.d
>  create mode 100644 ld/testsuite/ld-riscv-elf/relax-max-align-gp.s
>
> diff --git a/bfd/elfnn-riscv.c b/bfd/elfnn-riscv.c
> index cf852636c9c..ed72704bd80 100644
> --- a/bfd/elfnn-riscv.c
> +++ b/bfd/elfnn-riscv.c
> @@ -4266,6 +4266,28 @@ typedef bool (*relax_func_t) (bfd *, asection *, asection *,
>                               riscv_pcgp_relocs *,
>                               bool undefined_weak);
>
> +/* Traverse all output sections in jtype, and return the max alignment.  */
> +
> +static bfd_vma
> +_bfd_riscv_get_max_alignment_in_jtype (asection *sec, bfd_vma base)
> +{
> +  unsigned int max_alignment_power = 0;
> +  asection *o;
> +
> +  if (sec == NULL)
> +    return 0;
> +
> +  for (o = sec->owner->sections; o != NULL; o = o->next)
> +    {
> +      if (VALID_JTYPE_IMM (sec_addr(o) - base)
> +         || VALID_ITYPE_IMM (sec_addr(o) + o->size - base))

Probably should be JTYPE?


> +       if (o->alignment_power > max_alignment_power)
> +         max_alignment_power = o->alignment_power;
> +    }
> +
> +  return (bfd_vma) 1 << max_alignment_power;
> +}
> +
>  /* Relax AUIPC + JALR into JAL.  */
>
>  static bool
> @@ -4294,6 +4316,15 @@ _bfd_riscv_relax_call (bfd *abfd, asection *sec, asection *sym_sec,
>        if (sym_sec->output_section == sec->output_section
>           && sym_sec->output_section != bfd_abs_section_ptr)
>         max_alignment = (bfd_vma) 1 << sym_sec->output_section->alignment_power;
> +      else
> +       {
> +         bfd_vma new_max_alignment =
> +           _bfd_riscv_get_max_alignment_in_jtype (sec,
> +                                                  (sec_addr (sec)
> +                                                   + rel->r_offset));
> +         if (new_max_alignment)
> +           max_alignment = new_max_alignment;
> +       }
>        foff += ((bfd_signed_vma) foff < 0 ? -max_alignment : max_alignment);
>      }
>
> @@ -4360,6 +4391,28 @@ _bfd_riscv_get_max_alignment (asection *sec)
>    return (bfd_vma) 1 << max_alignment_power;
>  }
>
> +/* Traverse all output sections in [gp-2K, gp+2K) and return the max alignment.  */
> +
> +static bfd_vma
> +_bfd_riscv_get_max_alignment_in_itype (asection *sec, bfd_vma gp)
> +{
> +  unsigned int max_alignment_power = 0;
> +  asection *o;
> +
> +  if (sec == NULL)
> +    return 0;
> +
> +  for (o = sec->owner->sections; o != NULL; o = o->next)
> +    {
> +      if (VALID_ITYPE_IMM (sec_addr(o) - gp)
> +         || VALID_ITYPE_IMM (sec_addr(o) + o->size - gp))
> +       if (o->alignment_power > max_alignment_power)
> +         max_alignment_power = o->alignment_power;
> +    }
> +
> +  return (bfd_vma) 1 << max_alignment_power;
> +}
> +
>
>  /* Relax non-PIC global variable references to GP-relative references.  */
>
>  static bool
> @@ -4391,6 +4444,13 @@ _bfd_riscv_relax_lui (bfd *abfd,
>        if (h->u.def.section->output_section == sym_sec->output_section
>           && sym_sec->output_section != bfd_abs_section_ptr)
>         max_alignment = (bfd_vma) 1 << sym_sec->output_section->alignment_power;
> +      else
> +       {
> +         /* Otherwise, consider the alignment of sections in [gp-2K,gp+2K). */
> +         bfd_vma new_max_alignment = _bfd_riscv_get_max_alignment_in_itype (sec, gp);
> +         if (new_max_alignment)
> +           max_alignment = new_max_alignment;
> +       }
>      }
>
>    /* Is the reference in range of x0 or gp?
> @@ -4656,6 +4716,13 @@ _bfd_riscv_relax_pc (bfd *abfd ATTRIBUTE_UNUSED,
>        if (h->u.def.section->output_section == sym_sec->output_section
>           && sym_sec->output_section != bfd_abs_section_ptr)
>         max_alignment = (bfd_vma) 1 << sym_sec->output_section->alignment_power;
> +      else if (!undefined_weak)
> +       {
> +         /* Otherwise, consider the alignment of sections in [gp-2K,gp+2K). */
> +         bfd_vma new_max_alignment = _bfd_riscv_get_max_alignment_in_itype (sec, gp);
> +         if (new_max_alignment)
> +           max_alignment = new_max_alignment;
> +       }
>      }
>
>    /* Is the reference in range of x0 or gp?
> diff --git a/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp b/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
> index df89e0ee68b..f38807b991e 100644
> --- a/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
> +++ b/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
> @@ -169,6 +169,8 @@ if [istarget "riscv*-*-*"] {
>      run_dump_test "attr-merge-priv-spec-failed-05"
>      run_dump_test "attr-merge-priv-spec-failed-06"
>      run_dump_test "attr-phdr"
> +    run_dump_test "relax-max-align-gp"
> +    run_dump_test "relax-max-align-call"
>      run_ld_link_tests [list \
>         [list "Weak reference 32" "-T weakref.ld -m[riscv_choose_ilp32_emul]" "" \
>             "-march=rv32i -mabi=ilp32" {weakref32.s} \
> diff --git a/ld/testsuite/ld-riscv-elf/relax-max-align-call.d b/ld/testsuite/ld-riscv-elf/relax-max-align-call.d
> new file mode 100644
> index 00000000000..490ad8c865e
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/relax-max-align-call.d
> @@ -0,0 +1,18 @@
> +#source: relax-max-align-call.s
> +#as: -march=rv64gc
> +#ld: -Trelax-max-align-call.ld
> +#objdump: -d
> +
> +.*:[   ]+file format .*
> +
> +
> +Disassembly of section .text1:
> +
> +0000000000100000 <_start>:
> +[      ]+100000:[      ]+79dff0ef[     ]+jal[  ]+1fff9c <foo>
> +[      ]+100004:[      ]+a001[         ]+j[    ]+100004 <_start\+0x4>
> +
> +Disassembly of section .text2:
> +
> +00000000001fff9c <foo>:
> +[      ]+1fff9c:[      ]+8082[         ]+ret
> diff --git a/ld/testsuite/ld-riscv-elf/relax-max-align-call.ld b/ld/testsuite/ld-riscv-elf/relax-max-align-call.ld
> new file mode 100644
> index 00000000000..91991ed0f41
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/relax-max-align-call.ld
> @@ -0,0 +1,22 @@
> +
> +ENTRY(_start)
> +
> +SECTIONS
> +{
> +       . = 0x100000;
> +
> +       .text1 : {
> +               *(.text1)
> +       }
> +
> +       . = 0x200000 - 100;
> +
> +       .text2 : {
> +               *(.text2)
> +       }
> +
> +       . = 0x300000;
> +       .data : {
> +               *(.data)
> +       }
> +}
> diff --git a/ld/testsuite/ld-riscv-elf/relax-max-align-call.s b/ld/testsuite/ld-riscv-elf/relax-max-align-call.s
> new file mode 100644
> index 00000000000..3335c0970e7
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/relax-max-align-call.s
> @@ -0,0 +1,23 @@
> +
> +.section .text1, "ax"
> +.global _start
> +.align 2
> +_start:
> +       call foo
> +       j .
> +       .size _start, . - _start
> +
> +.section .text2, "ax"
> +.align 2
> +.global foo
> +.type foo, @function
> +foo:
> +       ret
> +       .size foo, . - foo
> +
> +.data
> +.global gdata
> +.align 10
> +gdata:
> +       .long 0
> +       .size gdata, . - gdata
> diff --git a/ld/testsuite/ld-riscv-elf/relax-max-align-gp.d b/ld/testsuite/ld-riscv-elf/relax-max-align-gp.d
> new file mode 100644
> index 00000000000..637de426ee4
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/relax-max-align-gp.d
> @@ -0,0 +1,46 @@
> +#source: relax-max-align-gp.s
> +#ld:
> +#objdump: -d
> +
> +.*:[   ]+file format .*
> +
> +
> +Disassembly of section .text:
> +
> +0+[0-9a-f]+ <_start>:
> +.*:[   ]+[0-9a-f]+[    ]+add[  ]+.*<gdata>
> +.*:[   ]+[0-9a-f]+[    ]+jal[  ]+.*
> +.*:[   ]+[0-9a-f]+[    ]+j[    ]+.*
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +.*:[   ]+[0-9a-f]+[    ]+nop
> +
> +0+[0-9a-f]+ <func>:
> +.*:[   ]+[0-9a-f]+[    ]+ret
> +[      ]+...
> diff --git a/ld/testsuite/ld-riscv-elf/relax-max-align-gp.s b/ld/testsuite/ld-riscv-elf/relax-max-align-gp.s
> new file mode 100644
> index 00000000000..0d162ff4d93
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/relax-max-align-gp.s
> @@ -0,0 +1,29 @@
> +
> +.global _start
> +_start:
> +       lui   a0, %hi(gdata)
> +       addi  a0, a0, %lo(gdata)
> +       call func
> +       j .
> +       .size _start, . - _start
> +
> +.global func
> +.align 7
> +func:
> +       ret
> +       .size func, . - func
> +
> +.data
> +padding:
> +       .long 0
> +       .long 0
> +       .long 0
> +       .long 0
> +       .size padding, . - padding
> +
> +.global gdata
> +.type gdata, object
> +gdata:
> +       .zero 4
> +       .size gdata, . - gdata
> +
> --
> 2.37.0 (Apple Git-136)
>

  parent reply	other threads:[~2022-11-22 10:19 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-23  6:47 [PATCH] RISC-V: Optimize relax of GP " lifang_xia
2022-09-23  8:05 ` Nelson Chu
2022-09-23  9:09   ` Lifang Xia
2022-09-23  9:46 ` lifang_xia
2022-09-23 10:44   ` Nelson Chu
2022-09-24  1:54     ` Lifang Xia
2022-09-27  8:51       ` Nelson Chu
2022-10-27  3:19       ` [PATCH v2] RISC-V: Optimize relax of GP/call " lifang_xia
2022-11-09  2:52         ` Lifang Xia
2022-11-22 10:19         ` Nelson Chu [this message]
2022-11-22 16:19           ` Palmer Dabbelt

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