We've decided to standardize on two flags for RISC-V: "-march" sets the
target architecture (which determines which instructions can be
generated), and "-mabi" sets the target ABI. We needed to rework this
because the old flag set didn't support soft-float or single-float ABIs,
and didn't support an x32-style ABI on RISC-V.
Additionally, we've changed the behavior of the -march flag: it's now a
lot stricter and only parses things we can actually understand.
Additionally, it's now lowercase-only: the rationale is that while the
RISC-V ISA manual specifies that ISA strings are case-insensitive, in
Linux-land things are usually case-sensitive. Since this flag can be
used to determine library paths, we didn't want to bake some
case-insensitivity in there that would case trouble later.
This patch implements these two new flags and removes the old flags that
could conflict with these. There wasn't a RISC-V release before, so we
want to just support a clean flag set.
include/
* elf/riscv.h (EF_RISCV_SOFT_FLOAT): Don't define.
(EF_RISCV_FLOAT_ABI, EF_RISCV_FLOAT_ABI_SOFT): Define.
(EF_RISCV_FLOAT_ABI_SINGLE, EF_RISCV_FLOAT_ABI_DOUBLE): Define.
(EF_RISCV_FLOAT_ABI_QUAD): Define.
bfd/
* elfnn-riscv.c (_bfd_riscv_elf_merge_private_bfd_data): Use
EF_RISCV_FLOAT_ABI_SOFT instead of EF_RISCV_SOFT_FLOAT.
binutils/
* readelf.c (get_machine_flags): Use
EF_RISCV_FLOAT_ABI_{SOFT,SINGLE,DOBULE,QUAD) instead of
EF_RISCV_{SOFT,HARD}_FLOAT.
gas/
* config/tc-riscv.h (xlen): Delete.
* config/tc-riscv.c (xlen): Make static.
(abi_xlen): New variable.
(options): Replace OPTION_{M32,M64,MSOFT_FLOAT,MHARD_FLOAT,MRVC}
with OPTION_MABI.
(md_longopts): Likewise.
(md_parse_option): Likewise.
(riscv_elf_final_processing): Likewise.
* doc/as.texinfo (Target RISC-V options): Likewise.
* doc/c-riscv.texi (OPTIONS): Likewise.
* config/tc-riscv.c (float_mode): Removed.
(float_abi): New type, specifies the floating-point ABI.
(riscv_set_abi): New function.
(riscv_add_subset): Only allow lower-case ISA names and require
them to start with "rv".
(riscv_after_parse_args): Likewise.
opcodes/
* riscv-dis.c (riscv_disassemble_insn): Default to the ELF's
XLEN when none is provided.
Before this commit we didn't cleanly support CFI directives because the
internal offsets used to get relaxed which broke them. This patch
significantly reworks how we handle linker relaxations:
* DWARF is now properly supported
* There is a ".option norelax" to disable relaxations, for when users
write assembly that can't be relaxed (if it's to be later patched up,
for example).
* There is an additional _RELAX relocation that specifies when previous
relocations can be relaxed.
We're in the process of documenting the RISC-V ELF ABI, which will
include documentation of our relocations
https://github.com/riscv/riscv-elf-psabi-doc/blob/master/riscv-elf.md
but we expect that this relocation set will remain ABI compatible in the
future (ie, it's safe to release).
Thanks to Kuan-Lin Chen for figuring out how to correctly relax the
debug info!
include/
* elf/riscv.h: Add R_RISCV_TPREL_I through R_RISCV_SET32.
bfd/
* reloc.c (BFD_RELOC_RISCV_TPREL_I): New relocation.
(BFD_RELOC_RISCV_TPREL_S): Likewise.
(BFD_RELOC_RISCV_RELAX): Likewise.
(BFD_RELOC_RISCV_CFA): Likewise.
(BFD_RELOC_RISCV_SUB6): Likewise.
(BFD_RELOC_RISCV_SET8): Likewise.
(BFD_RELOC_RISCV_SET8): Likewise.
(BFD_RELOC_RISCV_SET16): Likewise.
(BFD_RELOC_RISCV_SET32): Likewise.
* elfnn-riscv.c (perform_relocation): Handle the new
relocations.
(_bfd_riscv_relax_tls_le): Likewise.
(_bfd_riscv_relax_align): Likewise.
(_bfd_riscv_relax_section): Likewise.
(howto_table): Likewise.
(riscv_reloc_map): Likewise.
(relax_func_t): New type.
(_bfd_riscv_relax_call): Add reserve_size argument, which
controls the maximal offset pessimism. Correct type of max_alignment.
(_bfd_riscv_relax_lui): Likewise.
(_bfd_riscv_relax_tls_le): Likewise.
(_bfd_riscv_relax_align): Likewise.
(_bfd_riscv_relax_section): Compute the required reserve size
when relocating and use it to when calling relax_func.
* bfd-in2.h: Regenerate.
* libbfd.h: Likewise.
gas/
* config/tc-riscv.c (riscv_set_options): Add relax.
(riscv_opts): Likewise.
(s_riscv_option): Add relax and norelax.
(riscv_apply_const_reloc): New function.
(append_insn): Move constant relocation handling to
riscv_apply_const_reloc.
(md_pcrel_from): Likewise.
(parse_relocation): Skip BFD_RELOC_UNUSED.
(md_pcrel_from): Handle BFD_RELOC_RISCV_SUB6,
BFD_RELOC_RISCV_RELAX, BFD_RELOC_RISCV_CFA.
(md_apply_fix): Likewise.
(riscv_pre_output_hook): New function.
* config/tc-riscv.h (md_pre_output_hook): Define.
(riscv_pre_output_hook): Declare.
(DWARF_CIE_DATA_ALIGNMENT): Always -4.
