For the lui and auipc relaxations, since the symbol value of an undefined weak
symbol is always be zero, we can optimize the patterns into a single LI/MV/ADDI
instruction.
bfd/
* elfnn-riscv.c (riscv_pcgp_hi_reloc): Add new field undefined_weak.
(riscv_record_pcgp_hi_reloc): New parameter undefined_weak.
Set undefined_weak field from it.
(relax_func_t): New parameter undefined_weak.
(_bfd_riscv_relax_call): New ignored parameter undefined_weak.
(_bfd_riscv_relax_tls_le): Likewise.
(_bfd_riscv_relax_align): Likewise.
(_bfd_riscv_relax_delete): Likewise.
(_bfd_riscv_relax_lui): New parameter undefined_weak. If true,
allow relaxing. For LO12* relocs, set rs1 to x0 when undefined_weak.
(_bfd_riscv_relax_pc): New parameter undefined_weak. For LO12* relocs,
set undefined_weak from hi_reloc. If true, allow relaxing. For LO12*
relocs, set rs1 to x0 when undefined_weak and change to non-pcrel
reloc.
(_bfd_riscv_relax_section): New local undefined_weak. Set for
undef weak relocs that can be relaxed. Pass to relax_func call.
ld/
* testsuite/ld-riscv-elf/weakref32.s: Add relaxable undef weak code.
* testsuite/ld-riscv-elf/weakref64.s: Likewise.
* testsuite/ld-riscv-elf/weakref32.d: Updated.
* testsuite/ld-riscv-elf/weakref64.d: Updated.
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README for LD
This is the GNU linker. It is distributed with other "binary
utilities" which should be in ../binutils. See ../binutils/README for
more general notes, including where to send bug reports.
There are many features of the linker:
* The linker uses a Binary File Descriptor library (../bfd)
that it uses to read and write object files. This helps
insulate the linker itself from the format of object files.
* The linker supports a number of different object file
formats. It can even handle multiple formats at once:
Read two input formats and write a third.
* The linker can be configured for cross-linking.
* The linker supports a control language.
* There is a user manual (ld.texi), as well as the
beginnings of an internals manual (ldint.texi).
Installation
============
See ../binutils/README.
If you want to make a cross-linker, you may want to specify
a different search path of -lfoo libraries than the default.
You can do this by setting the LIB_PATH variable in ./Makefile
or using the --with-lib-path configure switch.
To build just the linker, make the target all-ld from the top level
directory (one directory above this one).
Porting to a new target
=======================
See the ldint.texi manual.
Reporting bugs etc
===========================
See ../binutils/README.
Known problems
==============
The Solaris linker normally exports all dynamic symbols from an
executable. The GNU linker does not do this by default. This is
because the GNU linker tries to present the same interface for all
similar targets (in this case, all native ELF targets). This does not
matter for normal programs, but it can make a difference for programs
which try to dlopen an executable, such as PERL or Tcl. You can make
the GNU linker export all dynamic symbols with the -E or
--export-dynamic command line option.
HP/UX 9.01 has a shell bug that causes the linker scripts to be
generated incorrectly. The symptom of this appears to be "fatal error
- scanner input buffer overflow" error messages. There are various
workarounds to this:
* Build and install bash, and build with "make SHELL=bash".
* Update to a version of HP/UX with a working shell (e.g., 9.05).
* Replace "(. ${srcdir}/scripttempl/${SCRIPT_NAME}.sc)" in
genscripts.sh with "sh ${srcdir}..." (no parens) and make sure the
emulparams script used exports any shell variables it sets.
Copyright (C) 2012-2019 Free Software Foundation, Inc.
Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.
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