> diff --git a/gcc/common/config/riscv/riscv-common.cc b/gcc/common/config/riscv/riscv-common.cc
> index ebc1ed7d7e4..2b3ff1f5b8e 100644
> --- a/gcc/common/config/riscv/riscv-common.cc
> +++ b/gcc/common/config/riscv/riscv-common.cc
> @@ -102,6 +102,8 @@ static const riscv_implied_info_t riscv_implied_info[] =
> {"zvl32768b", "zvl16384b"},
> {"zvl65536b", "zvl32768b"},
> 
> + {"zfbfmin", "zfhmin"},
> +
> {"zfh", "zfhmin"},
> {"zfhmin", "f"},
> 
> @@ -1239,6 +1241,8 @@ static const riscv_ext_flag_table_t riscv_ext_flag_table[] =
> {"zvl16384b", &gcc_options::x_riscv_zvl_flags, MASK_ZVL16384B},
> {"zvl32768b", &gcc_options::x_riscv_zvl_flags, MASK_ZVL32768B},
> {"zvl65536b", &gcc_options::x_riscv_zvl_flags, MASK_ZVL65536B},
> + 
> + {"zfbfmin", &gcc_options::x_riscv_zf_subext, MASK_ZFBFMIN},
> 
> {"zfhmin", &gcc_options::x_riscv_zf_subext, MASK_ZFHMIN},
> {"zfh", &gcc_options::x_riscv_zf_subext, MASK_ZFH},
As kito says, there is no version information for the extension.
> diff --git a/gcc/config/riscv/iterators.md b/gcc/config/riscv/iterators.md
> index 5b70ab20758..6349f032bc8 100644
> --- a/gcc/config/riscv/iterators.md
> +++ b/gcc/config/riscv/iterators.md
> @@ -61,10 +61,15 @@
> ;; Iterator for hardware-supported floating-point modes.
> (define_mode_iterator ANYF [(SF "TARGET_HARD_FLOAT || TARGET_ZFINX")
> (DF "TARGET_DOUBLE_FLOAT || TARGET_ZDINX")
> - (HF "TARGET_ZFH || TARGET_ZHINX")])
> + (HF "TARGET_ZFH || TARGET_ZHINX") 
> + (BF "TARGET_ZFBFMIN")])
> +
> +;; Iterator for HImode constant generation.
> +(define_mode_iterator BFHF [BF HF])
> 
> ;; Iterator for floating-point modes that can be loaded into X registers.
> -(define_mode_iterator SOFTF [SF (DF "TARGET_64BIT") (HF "TARGET_ZFHMIN")])
> +(define_mode_iterator SOFTF [SF (DF "TARGET_64BIT") (HF "TARGET_ZFHMIN")
> + (BF "TARGET_ZFBFMIN")])
> 
> 
> ;; -------------------------------------------------------------------
> @@ -76,27 +81,27 @@
> (define_mode_attr size [(QI "b") (HI "h")])
> 
> ;; Mode attributes for loads.
> -(define_mode_attr load [(QI "lb") (HI "lh") (SI "lw") (DI "ld") (HF "flh") (SF "flw") (DF "fld")])
> +(define_mode_attr load [(QI "lb") (HI "lh") (SI "lw") (DI "ld") (BF "flh") (HF "flh") (SF "flw") (DF "fld")])
> 
> ;; Instruction names for integer loads that aren't explicitly sign or zero
> ;; extended. See riscv_output_move and LOAD_EXTEND_OP.
> (define_mode_attr default_load [(QI "lbu") (HI "lhu") (SI "lw") (DI "ld")])
> 
> ;; Mode attribute for FP loads into integer registers.
> -(define_mode_attr softload [(HF "lh") (SF "lw") (DF "ld")])
> +(define_mode_attr softload [(BF "lh") (HF "lh") (SF "lw") (DF "ld")])
> 
> ;; Instruction names for stores.
> -(define_mode_attr store [(QI "sb") (HI "sh") (SI "sw") (DI "sd") (HF "fsh") (SF "fsw") (DF "fsd")])
> +(define_mode_attr store [(QI "sb") (HI "sh") (SI "sw") (DI "sd") (BF "fsh") (HF "fsh") (SF "fsw") (DF "fsd")])
> 
> ;; Instruction names for FP stores from integer registers.
> -(define_mode_attr softstore [(HF "sh") (SF "sw") (DF "sd")])
> +(define_mode_attr softstore [(BF "sh") (HF "sh") (SF "sw") (DF "sd")])
> 
> ;; This attribute gives the best constraint to use for registers of
> ;; a given mode.
> (define_mode_attr reg [(SI "d") (DI "d") (CC "d")])
> 
> ;; This attribute gives the format suffix for floating-point operations.
> -(define_mode_attr fmt [(HF "h") (SF "s") (DF "d")])
> +(define_mode_attr fmt [(BF "h") (HF "h") (SF "s") (DF "d")])
> 
> ;; This attribute gives the integer suffix for floating-point conversions.
> (define_mode_attr ifmt [(SI "w") (DI "l")])
> @@ -106,7 +111,7 @@
> 
> ;; This attribute gives the upper-case mode name for one unit of a
> ;; floating-point mode.
> -(define_mode_attr UNITMODE [(HF "HF") (SF "SF") (DF "DF")])
> +(define_mode_attr UNITMODE [(BF "BF") (HF "HF") (SF "SF") (DF "DF")])
> 
> ;; This attribute gives the integer mode that has half the size of
> ;; the controlling mode.
> diff --git a/gcc/config/riscv/riscv-builtins.cc b/gcc/config/riscv/riscv-builtins.cc
> index 25ca407f9a9..e0c6f6834a5 100644
> --- a/gcc/config/riscv/riscv-builtins.cc
> +++ b/gcc/config/riscv/riscv-builtins.cc
> @@ -163,6 +163,7 @@ static GTY(()) int riscv_builtin_decl_index[NUM_INSN_CODES];
> riscv_builtin_decls[riscv_builtin_decl_index[(CODE)]]
> 
> tree riscv_float16_type_node = NULL_TREE;
> +tree riscv_bfloat16_type_node = NULL_TREE;
> 
> /* Return the function type associated with function prototype TYPE. */
> 
> @@ -190,7 +191,7 @@ riscv_build_function_type (enum riscv_function_type type)
> }
> 
> static void
> -riscv_init_builtin_types (void)
> +riscv_fp16_builtin_type (void)
> {
> /* Provide the _Float16 type and float16_type_node if needed. */
> if (!float16_type_node)
> @@ -208,6 +209,32 @@ riscv_init_builtin_types (void)
> "_Float16");
> }
> 
> +static void
> +riscv_bf16_builtin_type (void)
> +{
> + /* Provide the _bf16 type and bfloat16_type_node if needed. */
> + if (!bfloat16_type_node)
> + {
> + riscv_bfloat16_type_node = make_node (REAL_TYPE);
> + TYPE_PRECISION (riscv_bfloat16_type_node) = 16;
> + SET_TYPE_MODE (riscv_bfloat16_type_node, BFmode);
> + layout_type (riscv_bfloat16_type_node);
> + }
> + else
> + riscv_bfloat16_type_node = bfloat16_type_node;
> +
> + if (!maybe_get_identifier ("__bf16"))
> + lang_hooks.types.register_builtin_type (riscv_bfloat16_type_node,
> + "__bf16");
> +}
> +
> +static void
> +riscv_init_builtin_types (void)
> +{
> + riscv_fp16_builtin_type ();
> + riscv_bf16_builtin_type ();
> +}
> +
> /* Implement TARGET_INIT_BUILTINS. */
> 
> void
> diff --git a/gcc/config/riscv/riscv-modes.def b/gcc/config/riscv/riscv-modes.def
> index d5305efa8a6..93c22b09ed7 100644
> --- a/gcc/config/riscv/riscv-modes.def
> +++ b/gcc/config/riscv/riscv-modes.def
> @@ -21,6 +21,8 @@ along with GCC; see the file COPYING3. If not see
> 
> FLOAT_MODE (HF, 2, ieee_half_format);
> FLOAT_MODE (TF, 16, ieee_quad_format);
> +FLOAT_MODE (BF, 2, 0);
> +ADJUST_FLOAT_FORMAT (BF, &arm_bfloat_half_format);
> 
> /* Vector modes. */
> 
> diff --git a/gcc/config/riscv/riscv-opts.h b/gcc/config/riscv/riscv-opts.h
> index ff398c0a2ae..e5791019912 100644
> --- a/gcc/config/riscv/riscv-opts.h
> +++ b/gcc/config/riscv/riscv-opts.h
> @@ -168,9 +168,11 @@ enum stack_protector_guard {
> 
> #define MASK_ZFHMIN (1 << 0)
> #define MASK_ZFH (1 << 1)
> +#define MASK_ZFBFMIN (1 << 2)
> 
> #define TARGET_ZFHMIN ((riscv_zf_subext & MASK_ZFHMIN) != 0)
> #define TARGET_ZFH ((riscv_zf_subext & MASK_ZFH) != 0)
> +#define TARGET_ZFBFMIN ((riscv_zf_subext & MASK_ZFBFMIN) != 0)
> 
> #define MASK_ZMMUL (1 << 0)
> #define TARGET_ZMMUL ((riscv_zm_subext & MASK_ZMMUL) != 0)
> diff --git a/gcc/config/riscv/riscv-vector-switch.def b/gcc/config/riscv/riscv-vector-switch.def
> index 8e4aed40338..8808d0f9b44 100644
> --- a/gcc/config/riscv/riscv-vector-switch.def
> +++ b/gcc/config/riscv/riscv-vector-switch.def
> @@ -75,7 +75,7 @@ n = SEW/LMUL
> |Types|n=1 |n=2 |n=4 |n=8 |n=16 |n=32 |n=64|
> |bool |VNx32BI|VNx16BI|VNx8BI|VNx4BI|VNx2BI|VNx1BI|N/A |
> 
> -TODO: FP16 vector needs support of 'zvfh', we don't support it yet. */
> +TODO: FP16 vector needs support of 'zvfh' and 'zvfbfmin', we don't support it yet. */
> 
> /* Return 'REQUIREMENT' for machine_mode 'MODE'.
> For example: 'MODE' = VNx64BImode needs TARGET_MIN_VLEN > 32. */
> @@ -120,7 +120,7 @@ ENTRY (VNx4HI, true, LMUL_2, 8, LMUL_1, 16)
> ENTRY (VNx2HI, true, LMUL_1, 16, LMUL_F2, 32)
> ENTRY (VNx1HI, true, LMUL_F2, 32, LMUL_F4, 64)
> 
> -/* TODO:Disable all FP16 vector, enable them when 'zvfh' is supported. */
> +/* TODO:Disable all FP16 vector, enable them when 'zvfh' and 'zvfbfmin' is supported. */
> ENTRY (VNx32HF, false, LMUL_RESERVED, 0, LMUL_8, 2)
> ENTRY (VNx16HF, false, LMUL_8, 2, LMUL_4, 4)
> ENTRY (VNx8HF, false, LMUL_4, 4, LMUL_2, 8)
> diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
> index f11b7949a49..2ddbdfa424a 100644
> --- a/gcc/config/riscv/riscv.cc
> +++ b/gcc/config/riscv/riscv.cc
> @@ -3192,7 +3192,11 @@ riscv_emit_float_compare (enum rtx_code *code, rtx *op0, rtx *op1)
> else if (GET_MODE (cmp_op0) == HFmode && TARGET_64BIT) \
> emit_insn (gen_f##CMP##_quiethfdi4 (*op0, cmp_op0, cmp_op1)); \
> else if (GET_MODE (cmp_op0) == HFmode) \
> - emit_insn (gen_f##CMP##_quiethfsi4 (*op0, cmp_op0, cmp_op1)); \
> + emit_insn (gen_f##CMP##_quietbfsi4 (*op0, cmp_op0, cmp_op1)); \
> + else if (GET_MODE (cmp_op0) == BFmode && TARGET_64BIT) \
> + emit_insn (gen_f##CMP##_quietbfdi4 (*op0, cmp_op0, cmp_op1)); \
> + else if (GET_MODE (cmp_op0) == BFmode) \
> + emit_insn (gen_f##CMP##_quietbfsi4 (*op0, cmp_op0, cmp_op1)); \
> else \
> gcc_unreachable (); \
> *op1 = const0_rtx; \
> @@ -6699,7 +6703,13 @@ riscv_mangle_type (const_tree type)
> {
> /* Half-precision float, _Float16 is "DF16_". */
> if (TREE_CODE (type) == REAL_TYPE && TYPE_PRECISION (type) == 16)
> - return "DF16_";
> + {
> + if (TYPE_MAIN_VARIANT (type) == float16_type_node)
> + return "DF16_";
The conditions here are very likely to be false, even if "TYPE_MODE (type) == HFmode",
there may be a risk of ICE, I'm not sure.
> + 
> + if (TYPE_MODE (type) == BFmode)
> + return "DF16b";
> + } 
> 
> /* Mangle all vector type for vector extension. */
> /* The mangle name follows the rule of RVV LLVM
> @@ -6720,19 +6730,19 @@ riscv_mangle_type (const_tree type)
> static bool
> riscv_scalar_mode_supported_p (scalar_mode mode)
> {
> - if (mode == HFmode)
> + if (mode == HFmode || mode == BFmode)
> return true;
> else
> return default_scalar_mode_supported_p (mode);
> }
> 
> /* Implement TARGET_LIBGCC_FLOATING_MODE_SUPPORTED_P - return TRUE
> - if MODE is HFmode, and punt to the generic implementation otherwise. */
> + if MODE is HFmode or BFmode, and punt to the generic implementation otherwise. */
> 
> static bool
> riscv_libgcc_floating_mode_supported_p (scalar_float_mode mode)
> {
> - if (mode == HFmode)
> + if (mode == HFmode || mode == BFmode)
> return true;
> else
> return default_libgcc_floating_mode_supported_p (mode);
> @@ -6804,6 +6814,23 @@ riscv_init_libfuncs (void)
> set_optab_libfunc (ge_optab, HFmode, NULL);
> set_optab_libfunc (gt_optab, HFmode, NULL);
> set_optab_libfunc (unord_optab, HFmode, NULL);
> +
> + /* Bfloat16*/
> + /* Arithmetic. */
> + set_optab_libfunc (add_optab, BFmode, NULL);
> + set_optab_libfunc (sdiv_optab, BFmode, NULL);
> + set_optab_libfunc (smul_optab, BFmode, NULL);
> + set_optab_libfunc (neg_optab, BFmode, NULL);
> + set_optab_libfunc (sub_optab, BFmode, NULL);
> +
> + /* Comparisons. */
> + set_optab_libfunc (eq_optab, BFmode, NULL);
> + set_optab_libfunc (ne_optab, BFmode, NULL);
> + set_optab_libfunc (lt_optab, BFmode, NULL);
> + set_optab_libfunc (le_optab, BFmode, NULL);
> + set_optab_libfunc (ge_optab, BFmode, NULL);
> + set_optab_libfunc (gt_optab, BFmode, NULL);
> + set_optab_libfunc (unord_optab, BFmode, NULL);
> }
> 
> #if CHECKING_P
> diff --git a/gcc/config/riscv/riscv.md b/gcc/config/riscv/riscv.md
> index 05924e9bbf1..89b10bada5e 100644
> --- a/gcc/config/riscv/riscv.md
> +++ b/gcc/config/riscv/riscv.md
> @@ -158,7 +158,7 @@
> (const_string "unknown"))
> 
> ;; Main data type used by the insn
> -(define_attr "mode" "unknown,none,QI,HI,SI,DI,TI,HF,SF,DF,TF,
> +(define_attr "mode" "unknown,none,QI,HI,SI,DI,TI,BF,HF,SF,DF,TF,
> VNx1BI,VNx2BI,VNx4BI,VNx8BI,VNx16BI,VNx32BI,VNx64BI,
> VNx1QI,VNx2QI,VNx4QI,VNx8QI,VNx16QI,VNx32QI,VNx64QI,
> VNx1HI,VNx2HI,VNx4HI,VNx8HI,VNx16HI,VNx32HI,
> @@ -1330,15 +1330,25 @@
> [(set_attr "type" "fcvt")
> (set_attr "mode" "HF")])
> 
> -(define_insn "truncdfhf2"
> - [(set (match_operand:HF 0 "register_operand" "=f")
> - (float_truncate:HF
> +(define_insn "truncsfbf2"
> + [(set (match_operand:BF 0 "register_operand" "=f")
> + (float_truncate:BF
> + (match_operand:SF 1 "register_operand" " f")))]
> + "TARGET_ZFBFMIN"
> + "fcvt.bf16.s\t%0,%1"
> + [(set_attr "type" "fcvt")
> + (set_attr "mode" "BF")])
> +
> +(define_insn "truncdf<BFHF:mode>2"
> + [(set (match_operand:BFHF 0 "register_operand" "=f")
> + (float_truncate:BFHF
> (match_operand:DF 1 "register_operand" " f")))]
> "(TARGET_ZFHMIN && TARGET_DOUBLE_FLOAT) ||
> - (TARGET_ZHINXMIN && TARGET_ZDINX)"
> + (TARGET_ZHINXMIN && TARGET_ZDINX) || 
> + (TARGET_ZFBFMIN && TARGET_DOUBLE_FLOAT)"
> "fcvt.h.d\t%0,%1"
> [(set_attr "type" "fcvt")
> - (set_attr "mode" "HF")])
> + (set_attr "mode" "<BFHF:MODE>")])
> 
This may not be correct, because when double is converted to__bf16, it
should be converted to float first and then to__bf16. Right?
> ;;
> ;; ....................
> @@ -1466,6 +1476,15 @@
> [(set_attr "type" "fcvt")
> (set_attr "mode" "SF")])
> 
> +(define_insn "extendbfsf2"
> + [(set (match_operand:SF 0 "register_operand" "=f")
> + (float_extend:SF
> + (match_operand:BF 1 "register_operand" " f")))]
> + "TARGET_ZFBFMIN"
> + "fcvt.s.bf16\t%0,%1"
> + [(set_attr "type" "fcvt")
> + (set_attr "mode" "SF")])
> +
> (define_insn "extendsfdf2"
> [(set (match_operand:DF 0 "register_operand" "=f")
> (float_extend:DF
> @@ -1475,15 +1494,16 @@
> [(set_attr "type" "fcvt")
> (set_attr "mode" "DF")])
> 
> -(define_insn "extendhfdf2"
> +(define_insn "extend<BFHF:mode>df2"
> [(set (match_operand:DF 0 "register_operand" "=f")
> (float_extend:DF
> - (match_operand:HF 1 "register_operand" " f")))]
> + (match_operand:BFHF 1 "register_operand" " f")))]
> "(TARGET_ZFHMIN && TARGET_DOUBLE_FLOAT) ||
> - (TARGET_ZHINXMIN && TARGET_ZDINX)"
> + (TARGET_ZHINXMIN && TARGET_ZDINX) ||
> + (TARGET_ZFBFMIN && TARGET_DOUBLE_FLOAT)"
> "fcvt.d.h\t%0,%1"
> [(set_attr "type" "fcvt")
> - (set_attr "mode" "DF")])
> + (set_attr "mode" "<BFHF:MODE>")])
> 
Same problem with truncdfbf2.
> ;; 16-bit floating point moves
> (define_expand "movhf"
> @@ -1515,6 +1535,35 @@
> [(set_attr "move_type" "fmove,move,load,store,mtc,mfc")
> (set_attr "mode" "HF")])
> 
> +(define_expand "movbf"
> + [(set (match_operand:BF 0 "")
> + (match_operand:BF 1 ""))]
> + ""
> +{
> + if (riscv_legitimize_move (BFmode, operands[0], operands[1]))
> + DONE;
> +})
> +
> +(define_insn "*movbf_hardfloat"
> + [(set (match_operand:BF 0 "nonimmediate_operand" "=f,f,f,m,m,*f,*r, *r,*r,*m")
> + (match_operand:BF 1 "move_operand" " f,G,m,f,G,*r,*f,*G*r,*m,*r"))]
> + "TARGET_ZFBFMIN
> + && (register_operand (operands[0], BFmode)
> + || reg_or_0_operand (operands[1], BFmode))"
> + { return riscv_output_move (operands[0], operands[1]); }
> + [(set_attr "move_type" "fmove,mtc,fpload,fpstore,store,mtc,mfc,move,load,store")
> + (set_attr "mode" "BF")])
> +
> +(define_insn "*movbf_softfloat"
> + [(set (match_operand:BF 0 "nonimmediate_operand" "=f, r,r,m,*f,*r")
> + (match_operand:BF 1 "move_operand" " f,Gr,m,r,*r,*f"))]
> + "!TARGET_ZFHMIN
> + && (register_operand (operands[0], BFmode)
> + || reg_or_0_operand (operands[1], BFmode))"
> + { return riscv_output_move (operands[0], operands[1]); }
> + [(set_attr "move_type" "fmove,move,load,store,mtc,mfc")
> + (set_attr "mode" "BF")])
> +
Maybe merge with movhf, movhf_hardfloat and *movhf_softfloat?
> ;;
> ;; ....................
> ;;
> diff --git a/libgcc/config/riscv/sfp-machine.h b/libgcc/config/riscv/sfp-machine.h
> index ded594d75d8..2ed7cbf3a30 100644
> --- a/libgcc/config/riscv/sfp-machine.h
> +++ b/libgcc/config/riscv/sfp-machine.h
> @@ -41,6 +41,7 @@ see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
> #define _FP_DIV_MEAT_D(R,X,Y) _FP_DIV_MEAT_2_udiv(D,R,X,Y)
> #define _FP_DIV_MEAT_Q(R,X,Y) _FP_DIV_MEAT_4_udiv(Q,R,X,Y)
> 
> +#define _FP_NANFRAC_B _FP_QNANBIT_B
> #define _FP_NANFRAC_H _FP_QNANBIT_H
> #define _FP_NANFRAC_S _FP_QNANBIT_S
> #define _FP_NANFRAC_D _FP_QNANBIT_D, 0
> @@ -64,6 +65,7 @@ see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
> #define _FP_DIV_MEAT_D(R,X,Y) _FP_DIV_MEAT_1_udiv_norm(D,R,X,Y)
> #define _FP_DIV_MEAT_Q(R,X,Y) _FP_DIV_MEAT_2_udiv(Q,R,X,Y)
> 
> +#define _FP_NANFRAC_B _FP_QNANBIT_B
> #define _FP_NANFRAC_H _FP_QNANBIT_H
> #define _FP_NANFRAC_S _FP_QNANBIT_S
> #define _FP_NANFRAC_D _FP_QNANBIT_D
> @@ -82,6 +84,7 @@ typedef unsigned int UTItype __attribute__ ((mode (TI)));
> typedef int __gcc_CMPtype __attribute__ ((mode (__libgcc_cmp_return__)));
> #define CMPtype __gcc_CMPtype
> 
> +#define _FP_NANSIGN_B 0
> #define _FP_NANSIGN_H 0
> #define _FP_NANSIGN_S 0
> #define _FP_NANSIGN_D 0
> diff --git a/libgcc/config/riscv/t-softfp32 b/libgcc/config/riscv/t-softfp32
> index 55261f98383..dc85ff79c1c 100644
> --- a/libgcc/config/riscv/t-softfp32
> +++ b/libgcc/config/riscv/t-softfp32
> @@ -42,7 +42,9 @@ softfp_extras := divsf3 divdf3 divtf3
> 
> endif
> 
> -softfp_extensions += hfsf hfdf hftf
> -softfp_truncations += tfhf dfhf sfhf
> +softfp_extensions += hfsf hfdf hftf bfsf bfdf bftf
bfdf and bftf do not seem to be implemented
> +softfp_truncations += tfhf dfhf sfhf tfbf dfbf sfhf
sfhf repeat, the last one should be sfbf
hfbf may also be required?
> softfp_extras += fixhfsi fixhfdi fixunshfsi fixunshfdi \
> - floatsihf floatdihf floatunsihf floatundihf
> + floatsihf floatdihf floatunsihf floatundihf \
> + fixbfsi fixbfdi fixunsbfsi fixunsbfdi \
> + floatsibf floatdibf floatunsibf floatundibf
 fixbfsi, fixbfdi, fixunsbfsi, fixunsbfdi, floatsibf and floatunsibf do
 not seem to be implemented.