RISC-V: Add support for the Zfa extension

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.

	* opcode/riscv-opc.h (MATCH_FLI_H): New.
	(MASK_FLI_H): New.
	(MATCH_FMINM_H): New.
	(MASK_FMINM_H): New.
	(MATCH_FMAXM_H): New.
	(MASK_FMAXM_H): New.
	(MATCH_FROUND_H): New.
	(MASK_FROUND_H): New.
	(MATCH_FROUNDNX_H): New.
	(MASK_FROUNDNX_H): New.
	(MATCH_FLTQ_H): New.
	(MASK_FLTQ_H): New.
	(MATCH_FLEQ_H): New.
	(MASK_FLEQ_H): New.
	(MATCH_FLI_S): New.
	(MASK_FLI_S): New.
	(MATCH_FMINM_S): New.
	(MASK_FMINM_S): New.
	(MATCH_FMAXM_S): New.
	(MASK_FMAXM_S): New.
	(MATCH_FROUND_S): New.
	(MASK_FROUND_S): New.
	(MATCH_FROUNDNX_S): New.
	(MASK_FROUNDNX_S): New.
	(MATCH_FLTQ_S): New.
	(MASK_FLTQ_S): New.
	(MATCH_FLEQ_S): New.
	(MASK_FLEQ_S): New.
	(MATCH_FLI_D): New.
	(MASK_FLI_D): New.
	(MATCH_FMINM_D): New.
	(MASK_FMINM_D): New.
	(MATCH_FMAXM_D): New.
	(MASK_FMAXM_D): New.
	(MATCH_FROUND_D): New.
	(MASK_FROUND_D): New.
	(MATCH_FROUNDNX_D): New.
	(MASK_FROUNDNX_D): New.
	(MATCH_FLTQ_D): New.
	(MASK_FLTQ_D): New.
	(MATCH_FLEQ_D): New.
	(MASK_FLEQ_D): New.
	(MATCH_FLI_Q): New.
	(MASK_FLI_Q): New.
	(MATCH_FMINM_Q): New.
	(MASK_FMINM_Q): New.
	(MATCH_FMAXM_Q): New.
	(MASK_FMAXM_Q): New.
	(MATCH_FROUND_Q): New.
	(MASK_FROUND_Q): New.
	(MATCH_FROUNDNX_Q): New.
	(MASK_FROUNDNX_Q): New.
	(MATCH_FLTQ_Q): New.
	(MASK_FLTQ_Q): New.
	(MATCH_FLEQ_Q): New.
	(MASK_FLEQ_Q): New.
	(MATCH_FCVTMOD_W_D): New.
	(MASK_FCVTMOD_W_D): New.
	(MATCH_FMVH_X_D): New.
	(MASK_FMVH_X_D): New.
	(MATCH_FMVH_X_Q): New.
	(MASK_FMVH_X_Q): New.
	(MATCH_FMVP_D_X): New.
	(MASK_FMVP_D_X): New.
	(MATCH_FMVP_Q_X): New.
	(MASK_FMVP_Q_X): New.
	(DECLARE_INSN): New.
	* opcode/riscv.h (enum riscv_insn_class): Add instruction
	classes for the Zfa extension.

opcodes/ChangeLog:

	* riscv-dis.c (print_insn_args): Add support for
	new format string directive 'Wfv'.
	* riscv-opc.c: Add Zfa instructions.

Co-Developed-by: Tsukasa OI <research_trasio@irq.a4lg.com>
Signed-off-by: Christoph Müllner <christoph.muellner@vrull.eu>
Co-Developed-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>

2 files changed, 80 insertions, 0 deletions

diff --git a/opcodes/riscv-dis.c b/opcodes/riscv-dis.c
index 108baeb..576cd24 100644
--- a/opcodes/riscv-dis.c
+++ b/opcodes/riscv-dis.c
@@ -595,6 +595,21 @@ print_insn_args (const char *oparg, insn_t l, bfd_vma pc, disassemble_info *info
 		    goto undefined_modifier;
 		  }
 		  break;
+	      case 'f':
+		switch (*++oparg)
+		  {
+		  case 'v':
+		    if (riscv_fli_symval[rs1])
+		      print (info->stream, dis_style_text, "%s",
+			     riscv_fli_symval[rs1]);
+		    else
+		      print (info->stream, dis_style_immediate, "%a",
+			     riscv_fli_numval[rs1]);
+		    break;
+		  default:
+		    goto undefined_modifier;
+		  }
+		break;
 	      default:
 		goto undefined_modifier;
 	      }
@@ -643,6 +658,7 @@ print_insn_args (const char *oparg, insn_t l, bfd_vma pc, disassemble_info *info
 	      }
 	  }
 	  break;
+
 	default:
 	undefined_modifier:
 	  /* xgettext:c-format */
diff --git a/opcodes/riscv-opc.c b/opcodes/riscv-opc.c
index 2b2dce1..c607e09 100644
--- a/opcodes/riscv-opc.c
+++ b/opcodes/riscv-opc.c
@@ -110,6 +110,27 @@ const char * const riscv_vma[2] =
   "mu", "ma"
 };
 
+/* The FLI.[HSDQ] symbolic constants (NULL for numeric constant).  */
+const char * const riscv_fli_symval[32] =
+{
+  NULL,  "min", NULL,  NULL,  NULL,  NULL,  NULL,  NULL,
+  NULL,  NULL,  NULL,  NULL,  NULL,  NULL,  NULL,  NULL,
+  NULL,  NULL,  NULL,  NULL,  NULL,  NULL,  NULL,  NULL,
+  NULL,  NULL,  NULL,  NULL,  NULL,  NULL,  "inf", "nan",
+};
+
+/* The FLI.[HSDQ] numeric constants (0.0 for symbolic constants).
+   The constants use the hex floating-point literal representation
+   that is printed when using the printf %a format specifier,
+   which matches the output that is generated by the disassembler.  */
+const float riscv_fli_numval[32] =
+{
+  -0x1p+0, 0x0p+0, 0x1p-16, 0x1p-15, 0x1p-8, 0x1p-7, 0x1p-4, 0x1p-3,
+  0x1p-2, 0x1.4p-2, 0x1.8p-2, 0x1.cp-2, 0x1p-1, 0x1.4p-1, 0x1.8p-1, 0x1.cp-1,
+  0x1p+0, 0x1.4p+0, 0x1.8p+0, 0x1.cp+0, 0x1p+1, 0x1.4p+1, 0x1.8p+1, 0x1p+2,
+  0x1p+3, 0x1p+4, 0x1p+7, 0x1p+8, 0x1p+15, 0x1p+16, 0x0p+0, 0x0p+0
+};
+
 /* The order of overloaded instructions matters.  Label arguments and
    register arguments look the same. Instructions that can have either
    for arguments must apear in the correct order in this table for the
@@ -944,6 +965,49 @@ const struct riscv_opcode riscv_opcodes[] =
 {"wrs.nto",    0, INSN_CLASS_ZAWRS, "", MATCH_WRS_NTO, MASK_WRS_NTO, match_opcode, 0 },
 {"wrs.sto",    0, INSN_CLASS_ZAWRS, "", MATCH_WRS_STO, MASK_WRS_STO, match_opcode, 0 },
 
+/* Zfa instructions.  */
+{"fli.s",       0, INSN_CLASS_ZFA,         "D,Wfv", MATCH_FLI_S, MASK_FLI_S, match_opcode, 0 },
+{"fli.d",       0, INSN_CLASS_D_AND_ZFA,   "D,Wfv", MATCH_FLI_D, MASK_FLI_D, match_opcode, 0 },
+{"fli.q",       0, INSN_CLASS_Q_AND_ZFA,   "D,Wfv", MATCH_FLI_Q, MASK_FLI_Q, match_opcode, 0 },
+{"fli.h",       0, INSN_CLASS_ZFH_AND_ZFA, "D,Wfv", MATCH_FLI_H, MASK_FLI_H, match_opcode, 0 },
+{"fminm.s",     0, INSN_CLASS_ZFA,         "D,S,T", MATCH_FMINM_S, MASK_FMINM_S, match_opcode, 0 },
+{"fmaxm.s",     0, INSN_CLASS_ZFA,         "D,S,T", MATCH_FMAXM_S, MASK_FMAXM_S, match_opcode, 0 },
+{"fminm.d",     0, INSN_CLASS_D_AND_ZFA,   "D,S,T", MATCH_FMINM_D, MASK_FMINM_D, match_opcode, 0 },
+{"fmaxm.d",     0, INSN_CLASS_D_AND_ZFA,   "D,S,T", MATCH_FMAXM_D, MASK_FMAXM_D, match_opcode, 0 },
+{"fminm.q",     0, INSN_CLASS_Q_AND_ZFA,   "D,S,T", MATCH_FMINM_Q, MASK_FMINM_Q, match_opcode, 0 },
+{"fmaxm.q",     0, INSN_CLASS_Q_AND_ZFA,   "D,S,T", MATCH_FMAXM_Q, MASK_FMAXM_Q, match_opcode, 0 },
+{"fminm.h",     0, INSN_CLASS_ZFH_AND_ZFA, "D,S,T", MATCH_FMINM_H, MASK_FMINM_H, match_opcode, 0 },
+{"fmaxm.h",     0, INSN_CLASS_ZFH_AND_ZFA, "D,S,T", MATCH_FMAXM_H, MASK_FMAXM_H, match_opcode, 0 },
+{"fround.s",    0, INSN_CLASS_ZFA,         "D,S",   MATCH_FROUND_S|MASK_RM, MASK_FROUND_S|MASK_RM, match_opcode, 0 },
+{"fround.s",    0, INSN_CLASS_ZFA,         "D,S,m", MATCH_FROUND_S, MASK_FROUND_S, match_opcode, 0 },
+{"froundnx.s",  0, INSN_CLASS_ZFA,         "D,S",   MATCH_FROUNDNX_S|MASK_RM, MASK_FROUNDNX_S|MASK_RM, match_opcode, 0 },
+{"froundnx.s",  0, INSN_CLASS_ZFA,         "D,S,m", MATCH_FROUNDNX_S, MASK_FROUNDNX_S, match_opcode, 0 },
+{"fround.d",    0, INSN_CLASS_D_AND_ZFA,   "D,S",   MATCH_FROUND_D|MASK_RM, MASK_FROUND_D|MASK_RM, match_opcode, 0 },
+{"fround.d",    0, INSN_CLASS_D_AND_ZFA,   "D,S,m", MATCH_FROUND_D, MASK_FROUND_D, match_opcode, 0 },
+{"froundnx.d",  0, INSN_CLASS_D_AND_ZFA,   "D,S",   MATCH_FROUNDNX_D|MASK_RM, MASK_FROUNDNX_D|MASK_RM, match_opcode, 0 },
+{"froundnx.d",  0, INSN_CLASS_D_AND_ZFA,   "D,S,m", MATCH_FROUNDNX_D, MASK_FROUNDNX_D, match_opcode, 0 },
+{"fround.q",    0, INSN_CLASS_Q_AND_ZFA,   "D,S",   MATCH_FROUND_Q|MASK_RM, MASK_FROUND_Q|MASK_RM, match_opcode, 0 },
+{"fround.q",    0, INSN_CLASS_Q_AND_ZFA,   "D,S,m", MATCH_FROUND_Q, MASK_FROUND_Q, match_opcode, 0 },
+{"froundnx.q",  0, INSN_CLASS_Q_AND_ZFA,   "D,S",   MATCH_FROUNDNX_Q|MASK_RM, MASK_FROUNDNX_Q|MASK_RM, match_opcode, 0 },
+{"froundnx.q",  0, INSN_CLASS_Q_AND_ZFA,   "D,S,m", MATCH_FROUNDNX_Q, MASK_FROUNDNX_Q, match_opcode, 0 },
+{"fround.h",    0, INSN_CLASS_ZFH_AND_ZFA, "D,S",   MATCH_FROUND_H|MASK_RM, MASK_FROUND_H|MASK_RM, match_opcode, 0 },
+{"fround.h",    0, INSN_CLASS_ZFH_AND_ZFA, "D,S,m", MATCH_FROUND_H, MASK_FROUND_H, match_opcode, 0 },
+{"froundnx.h",  0, INSN_CLASS_ZFH_AND_ZFA, "D,S",   MATCH_FROUNDNX_H|MASK_RM, MASK_FROUNDNX_H|MASK_RM, match_opcode, 0 },
+{"froundnx.h",  0, INSN_CLASS_ZFH_AND_ZFA, "D,S,m", MATCH_FROUNDNX_H, MASK_FROUNDNX_H, match_opcode, 0 },
+{"fcvtmod.w.d", 0, INSN_CLASS_D_AND_ZFA,   "d,S,m", MATCH_FCVTMOD_W_D, MASK_FCVTMOD_W_D, match_opcode, 0 },
+{"fmvh.x.d",   32, INSN_CLASS_D_AND_ZFA,   "d,S",   MATCH_FMVH_X_D, MASK_FMVH_X_D, match_opcode, 0 },
+{"fmvp.d.x",   32, INSN_CLASS_D_AND_ZFA,   "D,s,t", MATCH_FMVP_D_X, MASK_FMVP_D_X, match_opcode, 0 },
+{"fmvh.x.q",   64, INSN_CLASS_Q_AND_ZFA,   "d,S",   MATCH_FMVH_X_Q, MASK_FMVH_X_Q, match_opcode, 0 },
+{"fmvp.q.x",   64, INSN_CLASS_Q_AND_ZFA,   "D,s,t", MATCH_FMVP_Q_X, MASK_FMVP_Q_X, match_opcode, 0 },
+{"fltq.s",      0, INSN_CLASS_ZFA,         "d,S,T", MATCH_FLTQ_S, MASK_FLTQ_S, match_opcode, 0 },
+{"fleq.s",      0, INSN_CLASS_ZFA,         "d,S,T", MATCH_FLEQ_S, MASK_FLEQ_S, match_opcode, 0 },
+{"fltq.d",      0, INSN_CLASS_D_AND_ZFA,   "d,S,T", MATCH_FLTQ_D, MASK_FLTQ_D, match_opcode, 0 },
+{"fleq.d",      0, INSN_CLASS_D_AND_ZFA,   "d,S,T", MATCH_FLEQ_D, MASK_FLEQ_D, match_opcode, 0 },
+{"fltq.q",      0, INSN_CLASS_Q_AND_ZFA,   "d,S,T", MATCH_FLTQ_Q, MASK_FLTQ_Q, match_opcode, 0 },
+{"fleq.q",      0, INSN_CLASS_Q_AND_ZFA,   "d,S,T", MATCH_FLEQ_Q, MASK_FLEQ_Q, match_opcode, 0 },
+{"fltq.h",      0, INSN_CLASS_ZFH_AND_ZFA, "d,S,T", MATCH_FLTQ_H, MASK_FLTQ_H, match_opcode, 0 },
+{"fleq.h",      0, INSN_CLASS_ZFH_AND_ZFA, "d,S,T", MATCH_FLEQ_H, MASK_FLEQ_H, match_opcode, 0 },
+
 /* Zbb or zbkb instructions.  */
 {"clz",        0, INSN_CLASS_ZBB,  "d,s",   MATCH_CLZ, MASK_CLZ, match_opcode, 0 },
 {"ctz",        0, INSN_CLASS_ZBB,  "d,s",   MATCH_CTZ, MASK_CTZ, match_opcode, 0 },