From: Paul Mackerras Date: Mon, 31 Aug 2020 07:26:33 +0000 (+1000) Subject: FPU: Implement the frsp instruction X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=34b5d4a7b51bdae4e9994d11225b8216312eb793;p=microwatt.git FPU: Implement the frsp instruction This brings in the invalid exception for the case of frsp with a signalling NaN as input, and the need to be able to convert a signalling NaN to a quiet NaN. Signed-off-by: Paul Mackerras --- diff --git a/decode1.vhdl b/decode1.vhdl index 83444cf..284fb08 100644 --- a/decode1.vhdl +++ b/decode1.vhdl @@ -441,6 +441,7 @@ architecture behaviour of decode1 is 2#100000010# => (FPU, OP_FPOP, NONE, FRB, NONE, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC, '0', '0'), -- 2/8=fmr 2#100000100# => (FPU, OP_FPOP, NONE, FRB, NONE, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC, '0', '0'), -- 4/8=fnabs 2#100001000# => (FPU, OP_FPOP, NONE, FRB, NONE, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC, '0', '0'), -- 8/8=fabs + 2#110000000# => (FPU, OP_FPOP, NONE, FRB, NONE, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '0', RC, '0', '0'), -- 0/12=frsp 2#111011010# => (FPU, OP_FPOP_I, NONE, FRB, NONE, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC, '0', '0'), -- 26/14=fcfid 2#111011110# => (FPU, OP_FPOP_I, NONE, FRB, NONE, FRT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC, '0', '0'), -- 30/14=fcfidu others => illegal_inst diff --git a/fpu.vhdl b/fpu.vhdl index fecb7bb..7576562 100644 --- a/fpu.vhdl +++ b/fpu.vhdl @@ -39,6 +39,7 @@ architecture behaviour of fpu is DO_MCRFS, DO_MTFSB, DO_MTFSFI, DO_MFFS, DO_MTFSF, DO_FMR, DO_FCFID, + DO_FRSP, FINISH, NORMALIZE, ROUND_UFLOW, ROUND_OFLOW, ROUNDING, ROUNDING_2, ROUNDING_3, @@ -71,6 +72,7 @@ architecture behaviour of fpu is cr_mask : std_ulogic_vector(7 downto 0); old_exc : std_ulogic_vector(4 downto 0); update_fprf : std_ulogic; + quieten_nan : std_ulogic; tiny : std_ulogic; denorm : std_ulogic; round_mode : std_ulogic_vector(2 downto 0); @@ -217,7 +219,7 @@ architecture behaviour of fpu is -- Construct a DP floating-point result from components function pack_dp(sign: std_ulogic; class: fp_number_class; exp: signed(EXP_BITS-1 downto 0); - mantissa: std_ulogic_vector; single_prec: std_ulogic) + mantissa: std_ulogic_vector; single_prec: std_ulogic; quieten_nan: std_ulogic) return std_ulogic_vector is variable result : std_ulogic_vector(63 downto 0); begin @@ -238,7 +240,8 @@ architecture behaviour of fpu is result(62 downto 52) := "11111111111"; when NAN => result(62 downto 52) := "11111111111"; - result(51 downto 29) := mantissa(53 downto 31); + result(51) := quieten_nan or mantissa(53); + result(50 downto 29) := mantissa(52 downto 31); if single_prec = '0' then result(28 downto 0) := mantissa(30 downto 2); end if; @@ -348,6 +351,7 @@ begin variable round : std_ulogic_vector(1 downto 0); variable update_fx : std_ulogic; variable arith_done : std_ulogic; + variable invalid : std_ulogic; variable mant_nz : std_ulogic; variable min_exp : signed(EXP_BITS-1 downto 0); variable max_exp : signed(EXP_BITS-1 downto 0); @@ -384,6 +388,7 @@ begin if e_in.op = OP_FPOP_I then int_input := '1'; end if; + v.quieten_nan := '1'; v.tiny := '0'; v.denorm := '0'; v.round_mode := '0' & r.fpscr(FPSCR_RN+1 downto FPSCR_RN); @@ -429,6 +434,7 @@ begin fpscr_mask := (others => '1'); update_fx := '0'; arith_done := '0'; + invalid := '0'; renormalize := '0'; set_x := '0'; @@ -452,6 +458,8 @@ begin end if; when "01000" => v.state := DO_FMR; + when "01100" => + v.state := DO_FRSP; when "01110" => -- fcfid[u][s] v.state := DO_FCFID; @@ -552,6 +560,7 @@ begin opsel_a <= AIN_B; v.result_class := r.b.class; v.result_exp := r.b.exponent; + v.quieten_nan := '0'; if r.insn(9) = '1' then v.result_sign := '0'; -- fabs elsif r.insn(8) = '1' then @@ -567,6 +576,33 @@ begin v.instr_done := '1'; v.state := IDLE; + when DO_FRSP => + opsel_a <= AIN_B; + v.result_class := r.b.class; + v.result_sign := r.b.negative; + v.result_exp := r.b.exponent; + v.fpscr(FPSCR_FR) := '0'; + v.fpscr(FPSCR_FI) := '0'; + if r.b.class = NAN and r.b.mantissa(53) = '0' then + -- Signalling NAN + v.fpscr(FPSCR_VXSNAN) := '1'; + invalid := '1'; + end if; + set_x := '1'; + if r.b.class = FINITE then + if r.b.exponent < to_signed(-126, EXP_BITS) then + v.shift := r.b.exponent - to_signed(-126, EXP_BITS); + v.state := ROUND_UFLOW; + elsif r.b.exponent > to_signed(127, EXP_BITS) then + v.state := ROUND_OFLOW; + else + v.shift := to_signed(-2, EXP_BITS); + v.state := ROUNDING; + end if; + else + arith_done := '1'; + end if; + when DO_FCFID => v.result_sign := '0'; opsel_a <= AIN_B; @@ -735,8 +771,11 @@ begin end case; if arith_done = '1' then - v.writing_back := '1'; - v.update_fprf := '1'; + -- Enabled invalid exception doesn't write result or FPRF + if (invalid and r.fpscr(FPSCR_VE)) = '0' then + v.writing_back := '1'; + v.update_fprf := '1'; + end if; v.instr_done := '1'; v.state := IDLE; update_fx := '1'; @@ -827,7 +866,7 @@ begin fp_result <= r.r; else fp_result <= pack_dp(r.result_sign, r.result_class, r.result_exp, r.r, - r.single_prec); + r.single_prec, r.quieten_nan); end if; if r.update_fprf = '1' then v.fpscr(FPSCR_C downto FPSCR_FU) := result_flags(r.result_sign, r.result_class,