This patch adds support for the RISC-V Zfa extension,
which introduces additional floating-point instructions:
* fli (load-immediate) with pre-defined immediates
* fminm/fmaxm (like fmin/fmax but with different NaN behaviour)
* fround/froundmx (round to integer)
* fcvtmod.w.d (Modular Convert-to-Integer)
* fmv* to access high bits of FP registers in case XLEN < FLEN
* fleq/fltq (quiet comparison instructions)
Zfa defines its instructions in combination with the following
extensions:
* single-precision floating-point (F)
* double-precision floating-point (D)
* quad-precision floating-point (Q)
* half-precision floating-point (Zfh)
This patch is based on an earlier version from Tsukasa OI:
https://sourceware.org/pipermail/binutils/2022-September/122939.html
Most significant change to that commit is the switch from the rs1-field
value to the actual floating-point value in the last operand of the fli*
instructions. Everything that strtof() can parse is accepted and
the '%a' printf specifier is used to output hex floating-point literals
in the disassembly.
The Zfa specification is frozen (and has passed public review). It is
available as a chapter in "The RISC-V Instruction Set Manual: Volume 1":
https://github.com/riscv/riscv-isa-manual/releases
bfd/ChangeLog:
* elfxx-riscv.c (riscv_multi_subset_supports): Add instruction
class support for 'Zfa' extension.
(riscv_multi_subset_supports_ext): Likewise.
(riscv_implicit_subsets): Add 'Zfa' -> 'F' dependency.
gas/ChangeLog:
* config/tc-riscv.c (flt_lookup): New helper to lookup a float value
in an array.
(validate_riscv_insn): Add 'Wfv' as new format string directive.
(riscv_ip): Likewise.
* doc/c-riscv.texi: Add floating-point chapter and describe
limiations of the Zfa FP literal parsing.
* testsuite/gas/riscv/zfa-32.d: New test.
* testsuite/gas/riscv/zfa-32.s: New test.
* testsuite/gas/riscv/zfa-64.d: New test.
* testsuite/gas/riscv/zfa-64.s: New test.
* testsuite/gas/riscv/zfa-fail.d: New test.
* testsuite/gas/riscv/zfa-fail.l: New test.
* testsuite/gas/riscv/zfa-fail.s: New test.
* testsuite/gas/riscv/zfa.d: New test.
* testsuite/gas/riscv/zfa.s: New test.
* testsuite/gas/riscv/zfa.s: New test.