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ff6f4d9b2d
We currently delete bytes by shifting an entire BFD backwards to
overwrite the bytes we no longer need. The result is that relaxing a
BFD is quadratic time.
This patch adds an additional relocation that specifies a byte range
that will be deleted from the final object file, and adds a relaxation
pass (between the existing passes that delete bytes and the alignment
pass) that actually deletes the bytes. Note that deletion is still
quadratic time, and nothing uses R_RISCV_DELETE yet.
I've been meaning to go convert all the other relaxations to use
R_RISCV_DELETE and then make it faster, but this patch has been sitting
around for months so it looks like that won't happen for a bit. The
PCREL->GPREL relaxation that comes next uses this, and since we've been
using these two patches out of tree since I wrote them months ago I
figure it's better to just get them in now. I (or someone else :)) can
convert all the relocations later...
R_RISCV_DELETE will never be emitted into ELF objects, so therefor isn't
exposed to the rest of binutils. As such, we're not considering this as
part of the ABI.
bfd/ChangeLog
2017-10-19 Palmer Dabbelt <palmer@dabbelt.com>
* elfnn-riscv (R_RISCV_DELETE): New define.
(_bfd_riscv_relax_delete): New function.
(perform_relocation): Handle R_RISCV_DELETE.
(_bfd_riscv_relax_section): Likewise.
ld/ChangeLog
2017-10-19 Palmer Dabbelt <palmer@dabbelt.com>
* emultempl/riscvelf.em (riscv_elf_before_allocation): Add a
third relaxation pass.
69 lines
1.9 KiB
Plaintext
69 lines
1.9 KiB
Plaintext
# This shell script emits a C file. -*- C -*-
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# Copyright (C) 2004-2017 Free Software Foundation, Inc.
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#
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# This file is part of the GNU Binutils.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
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# MA 02110-1301, USA.
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fragment <<EOF
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#include "ldmain.h"
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#include "ldctor.h"
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#include "elf/riscv.h"
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#include "elfxx-riscv.h"
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static void
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riscv_elf_before_allocation (void)
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{
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gld${EMULATION_NAME}_before_allocation ();
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if (link_info.discard == discard_sec_merge)
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link_info.discard = discard_l;
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/* We always need at least some relaxation to handle code alignment. */
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if (RELAXATION_DISABLED_BY_USER)
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TARGET_ENABLE_RELAXATION;
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else
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ENABLE_RELAXATION;
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link_info.relax_pass = 3;
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}
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static void
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gld${EMULATION_NAME}_after_allocation (void)
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{
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int need_layout = 0;
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/* Don't attempt to discard unused .eh_frame sections until the final link,
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as we can't reliably tell if they're used until after relaxation. */
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if (!bfd_link_relocatable (&link_info))
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{
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need_layout = bfd_elf_discard_info (link_info.output_bfd, &link_info);
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if (need_layout < 0)
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{
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einfo (_("%X%P: .eh_frame/.stab edit: %E\n"));
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return;
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}
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}
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gld${EMULATION_NAME}_map_segments (need_layout);
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}
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EOF
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LDEMUL_BEFORE_ALLOCATION=riscv_elf_before_allocation
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LDEMUL_AFTER_ALLOCATION=gld${EMULATION_NAME}_after_allocation
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