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FPU: Reduce misc_sel to 3 bits

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Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
pull/442/head
Paul Mackerras 1 year ago
parent cf866ce910
commit 2731384a4b
1 changed files with 45 additions and 56 deletions
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101
fpu.vhdl
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@ -200,7 +200,7 @@ architecture behaviour of fpu is
signal r_lo_nz : std_ulogic;
signal r_gt_1 : std_ulogic;
signal s_nz : std_ulogic;
signal misc_sel : std_ulogic_vector(3 downto 0);
signal misc_sel : std_ulogic_vector(2 downto 0);
signal f_to_multiply : MultiplyInputType;
signal multiply_to_f : MultiplyOutputType;
signal msel_1 : std_ulogic_vector(1 downto 0);
@ -1150,7 +1150,7 @@ begin
opsel_r <= RES_SUM;
opsel_s <= S_ZERO;
carry_in <= '0';
misc_sel <= "0000";
misc_sel <= "000";
fpscr_mask := (others => '1');
update_fx := '0';
arith_done := '0';
@ -1498,13 +1498,14 @@ begin
when DO_FMRG =>
-- fmrgew, fmrgow
opsel_r <= RES_MISC;
misc_sel <= "01" & r.insn(8) & '0';
misc_sel <= "100";
v.writing_fpr := '1';
v.instr_done := '1';

when DO_MFFS =>
v.writing_fpr := '1';
opsel_r <= RES_MISC;
misc_sel <= "011";
case r.insn(20 downto 16) is
when "00000" =>
-- mffs
@ -2153,7 +2154,7 @@ begin
re_neg1 <= '1';
re_set_result <= '1';
opsel_r <= RES_MISC;
misc_sel <= "0111";
misc_sel <= "101";
-- set shift to 1
rs_con2 <= RSCON2_1;
v.state := NORMALIZE;
@ -2173,7 +2174,7 @@ begin

when RSQRT_1 =>
opsel_r <= RES_MISC;
misc_sel <= "0111";
misc_sel <= "101";
re_sel1 <= REXP1_BHALF;
re_neg1 <= '1';
re_set_result <= '1';
@ -2186,7 +2187,7 @@ begin
-- also transfer B (in R) to A
set_a := '1';
opsel_r <= RES_MISC;
misc_sel <= "0111";
misc_sel <= "101";
msel_1 <= MUL1_B;
msel_2 <= MUL2_LUT;
f_to_multiply.valid <= '1';
@ -2399,7 +2400,7 @@ begin
else
msb := r.r(63);
end if;
misc_sel <= '1' & r.insn(9 downto 8) & r.result_sign;
misc_sel <= "110";
if (r.insn(8) = '0' and msb /= r.result_sign) or
(r.insn(8) = '1' and msb /= '1') then
opsel_r <= RES_MISC;
@ -2414,10 +2415,7 @@ begin

when INT_OFLOW =>
opsel_r <= RES_MISC;
misc_sel <= '1' & r.insn(9 downto 8) & r.result_sign;
if r.b.class = NAN then
misc_sel(0) <= '1';
end if;
misc_sel <= "110";
v.fpscr(FPSCR_VXCVI) := '1';
invalid := '1';
arith_done := '1';
@ -2515,7 +2513,7 @@ begin
re_con2 <= RECON2_MAX;
re_set_result <= '1';
opsel_r <= RES_MISC;
misc_sel <= "001" & r.single_prec;
misc_sel <= "010";
arith_done := '1';
else
-- enabled overflow exception
@ -2761,7 +2759,7 @@ begin
-- less than 0.5, in which case we want to use 0.5, to avoid
-- infinite loops in some cases.
opsel_r <= RES_MISC;
misc_sel <= "0001";
misc_sel <= "001";
if multiply_to_f.valid = '1' then
v.first := '1';
if r.count = "11" then
@ -2774,7 +2772,7 @@ begin
-- Get 0.5 into R; it turns out the generated
-- QNaN mantissa is actually what we want
opsel_r <= RES_MISC;
misc_sel <= "0001";
misc_sel <= "001";
v.opsel_a := AIN_A;
-- set shift to 64
rs_con2 <= RSCON2_64;
@ -3136,7 +3134,7 @@ begin
v.instr_done := '1';
when IDIV_ZERO =>
opsel_r <= RES_MISC;
misc_sel <= "0101";
misc_sel <= "000";
v.xerc_result := v.xerc;
if r.oe = '1' then
v.xerc_result.ov := r.int_ovf;
@ -3176,7 +3174,7 @@ begin
invalid := '1';
v.result_class := NAN;
rsign := '0';
misc_sel <= "0001";
misc_sel <= "001";
opsel_r <= RES_MISC;
arith_done := '1';
end if;
@ -3342,50 +3340,41 @@ begin
when others =>
misc := (others => '0');
case misc_sel is
when "0000" =>
misc := x"00000000" & (r.fpscr and fpscr_mask);
when "0001" =>
-- generated QNaN mantissa
when "000" =>
-- zero result, used in idiv logic
when "001" =>
-- generated QNaN mantissa; also used for 0.5 in idiv logic
misc(QNAN_BIT) := '1';
when "0010" =>
-- mantissa of max representable DP number
misc(UNIT_BIT downto DP_LSB) := (others => '1');
when "0011" =>
-- mantissa of max representable SP number
when "010" =>
-- mantissa of max representable number, DP or SP
misc(UNIT_BIT downto SP_LSB) := (others => '1');
when "0100" =>
-- fmrgow result
misc := r.a.mantissa(31 downto 0) & r.b.mantissa(31 downto 0);
when "0110" =>
-- fmrgew result
misc := r.a.mantissa(63 downto 32) & r.b.mantissa(63 downto 32);
when "0111" =>
misc(SP_LSB-1 downto DP_LSB) := (others => not r.single_prec);
when "011" =>
-- read FPSCR
misc := x"00000000" & (r.fpscr and fpscr_mask);
when "100" =>
-- fmrgow/fmrgew result
if r.insn(8) = '0' then
misc := r.a.mantissa(31 downto 0) & r.b.mantissa(31 downto 0);
else
misc := r.a.mantissa(63 downto 32) & r.b.mantissa(63 downto 32);
end if;
when "101" =>
misc := std_ulogic_vector(shift_left(resize(unsigned(inverse_est), 64),
UNIT_BIT - 19));
when "1000" =>
-- max positive result for fctiw[z]
misc := x"000000007fffffff";
when "1001" =>
-- max negative result for fctiw[z]
misc := x"ffffffff80000000";
when "1010" =>
-- max positive result for fctiwu[z]
misc := x"00000000ffffffff";
when "1011" =>
-- max negative result for fctiwu[z]
misc := x"0000000000000000";
when "1100" =>
-- max positive result for fctid[z]
misc := x"7fffffffffffffff";
when "1101" =>
-- max negative result for fctid[z]
misc := x"8000000000000000";
when "1110" =>
-- max positive result for fctidu[z]
misc := x"ffffffffffffffff";
when "1111" =>
-- max negative result for fctidu[z]
misc := x"0000000000000000";
when "110" =>
-- max positive or negative result for fcti*
if r.result_sign = '0' and r.b.class /= NAN then
misc := x"000000007fffffff";
misc(31) := r.insn(8) or r.insn(9); -- unsigned or dword
misc(62 downto 32) := (others => r.insn(9)); -- dword
misc(63) := r.insn(8) and r.insn(8);
elsif r.insn(8) = '0' then
misc(63) := '1';
if r.insn(9) = '0' then
misc(62 downto 31) := (others => '1');
end if;
end if;
when others =>
end case;
result <= misc;

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