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xilinx_mult: Prepare for doing signed multiplication

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This rearranges the way that partial products are generated and summed
so that the partial products that could be negative in a signed
multiplier are now sign-extended.  The inputs are still zero-extended,
however.

The overflow detection logic now only detects 64-bit overflow, since
32-bit multiplications are handled in a separate multiplier.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
This commit is contained in:
Paul Mackerras
2022-08-08 17:06:46 +10:00
parent 595a758400
commit af9fe3467c
1 changed files with 144 additions and 131 deletions
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275
xilinx-mult.vhdl
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@@ -19,22 +19,24 @@ end entity multiply;
architecture behaviour of multiply is
signal m00_p, m01_p, m02_p, m03_p : std_ulogic_vector(47 downto 0);
signal m00_pc : std_ulogic_vector(47 downto 0);
signal m00_pc, m02_pc : std_ulogic_vector(47 downto 0);
signal m10_p, m11_p, m12_p, m13_p : std_ulogic_vector(47 downto 0);
signal m11_pc, m12_pc, m13_pc : std_ulogic_vector(47 downto 0);
signal m10_pc, m12_pc : std_ulogic_vector(47 downto 0);
signal m20_p, m21_p, m22_p, m23_p : std_ulogic_vector(47 downto 0);
signal m20_pc, m22_pc : std_ulogic_vector(47 downto 0);
signal pp0, pp1 : std_ulogic_vector(127 downto 0);
signal pp23 : std_ulogic_vector(127 downto 0);
signal sumlo : std_ulogic_vector(8 downto 0);
signal s0_pc, s1_pc : std_ulogic_vector(47 downto 0);
signal s0_carry, p0_carry : std_ulogic_vector(3 downto 0);
signal product : std_ulogic_vector(127 downto 0);
signal addend : std_ulogic_vector(127 downto 0);
signal s0_carry, p0_carry : std_ulogic_vector(3 downto 0);
signal p0_mask : std_ulogic_vector(47 downto 0);
signal p0_pat, p0_patb : std_ulogic;
signal p1_pat, p1_patb : std_ulogic;
signal req_32bit, r32_1 : std_ulogic;
signal rnot_1 : std_ulogic;
signal valid_1 : std_ulogic;
signal overflow, ovf_in : std_ulogic;
signal overflow : std_ulogic;
begin
addend <= m_in.addend;
@@ -55,12 +57,12 @@ begin
PREG => 1
)
port map (
A => "0000000" & m_in.data1(22 downto 0),
A => 6x"0" & m_in.data1(23 downto 0),
ACIN => (others => '0'),
ALUMODE => "0000",
B => '0' & m_in.data2(16 downto 0),
BCIN => (others => '0'),
C => "00000000000000" & addend(33 downto 0),
C => 14x"0" & addend(33 downto 0),
CARRYCASCIN => '0',
CARRYIN => '0',
CARRYINSEL => "000",
@@ -106,12 +108,14 @@ begin
BREG => 0,
CARRYINREG => 0,
CARRYINSELREG => 0,
CREG => 0,
INMODEREG => 0,
MREG => 1,
OPMODEREG => 0,
PREG => 0
)
port map (
A => "0000000" & m_in.data1(22 downto 0),
A => 6x"0" & m_in.data1(23 downto 0),
ACIN => (others => '0'),
ALUMODE => "0000",
B => '0' & m_in.data2(33 downto 17),
@@ -126,7 +130,7 @@ begin
CEALUMODE => '0',
CEB1 => '0',
CEB2 => '0',
CEC => '1',
CEC => '0',
CECARRYIN => '0',
CECTRL => '0',
CED => '0',
@@ -168,12 +172,12 @@ begin
PREG => 1
)
port map (
A => "0000000" & m_in.data1(22 downto 0),
A => 6x"0" & m_in.data1(23 downto 0),
ACIN => (others => '0'),
ALUMODE => "0000",
B => '0' & m_in.data2(50 downto 34),
BCIN => (others => '0'),
C => x"0000000" & "000" & addend(50 downto 34),
C => 24x"0" & addend(57 downto 34),
CARRYCASCIN => '0',
CARRYIN => '0',
CARRYINSEL => "000",
@@ -197,6 +201,7 @@ begin
OPMODE => "0110101",
P => m02_p,
PCIN => (others => '0'),
PCOUT => m02_pc,
RSTA => '0',
RSTALLCARRYIN => '0',
RSTALUMODE => '0',
@@ -220,17 +225,17 @@ begin
CARRYINSELREG => 0,
CREG => 0,
INMODEREG => 0,
MREG => 0,
MREG => 1,
OPMODEREG => 0,
PREG => 1
PREG => 0
)
port map (
A => "0000000" & m_in.data1(22 downto 0),
A => 6x"0" & m_in.data1(23 downto 0),
ACIN => (others => '0'),
ALUMODE => "0000",
B => "00000" & m_in.data2(63 downto 51),
BCIN => (others => '0'),
C => x"000000" & '0' & addend(73 downto 51),
C => (others => '0'),
CARRYCASCIN => '0',
CARRYIN => '0',
CARRYINSEL => "000",
@@ -245,15 +250,15 @@ begin
CECTRL => '0',
CED => '0',
CEINMODE => '0',
CEM => '0',
CEP => m_in.valid,
CEM => m_in.valid,
CEP => '0',
CLK => clk,
D => (others => '0'),
INMODE => "00000",
MULTSIGNIN => '0',
OPMODE => "0110101",
OPMODE => "1010101",
P => m03_p,
PCIN => (others => '0'),
PCIN => m02_pc,
RSTA => '0',
RSTALLCARRYIN => '0',
RSTALUMODE => '0',
@@ -277,16 +282,17 @@ begin
CARRYINSELREG => 0,
CREG => 0,
INMODEREG => 0,
MREG => 0,
OPMODEREG => 0,
PREG => 0
PREG => 1
)
port map (
A => "0000000000000" & m_in.data1(39 downto 23),
A => 6x"0" & m_in.data1(47 downto 24),
ACIN => (others => '0'),
ALUMODE => "0000",
B => '0' & m_in.data2(16 downto 0),
BCIN => (others => '0'),
C => x"000" & "00" & m01_p(39 downto 6),
C => (others => '0'),
CARRYCASCIN => '0',
CARRYIN => '0',
CARRYINSEL => "000",
@@ -301,15 +307,16 @@ begin
CECTRL => '0',
CED => '0',
CEINMODE => '0',
CEM => m_in.valid,
CEP => '0',
CEM => '0',
CEP => m_in.valid,
CLK => clk,
D => (others => '0'),
INMODE => "00000",
MULTSIGNIN => '0',
OPMODE => "0110101",
OPMODE => "0000101",
P => m10_p,
PCIN => (others => '0'),
PCOUT => m10_pc,
RSTA => '0',
RSTALLCARRYIN => '0',
RSTALUMODE => '0',
@@ -333,16 +340,17 @@ begin
CARRYINSELREG => 0,
CREG => 0,
INMODEREG => 0,
MREG => 1,
OPMODEREG => 0,
PREG => 0
)
port map (
A => "0000000000000" & m_in.data1(39 downto 23),
A => 6x"0" & m_in.data1(47 downto 24),
ACIN => (others => '0'),
ALUMODE => "0000",
B => '0' & m_in.data2(33 downto 17),
BCIN => (others => '0'),
C => x"000" & "00" & m02_p(39 downto 6),
C => (others => '0'),
CARRYCASCIN => '0',
CARRYIN => '0',
CARRYINSEL => "000",
@@ -363,10 +371,9 @@ begin
D => (others => '0'),
INMODE => "00000",
MULTSIGNIN => '0',
OPMODE => "0110101",
OPMODE => "1010101",
P => m11_p,
PCIN => (others => '0'),
PCOUT => m11_pc,
PCIN => m10_pc,
RSTA => '0',
RSTALLCARRYIN => '0',
RSTALUMODE => '0',
@@ -390,16 +397,17 @@ begin
CARRYINSELREG => 0,
CREG => 0,
INMODEREG => 0,
MREG => 0,
OPMODEREG => 0,
PREG => 0
PREG => 1
)
port map (
A => "0000000000000" & m_in.data1(39 downto 23),
A => 6x"0" & m_in.data1(47 downto 24),
ACIN => (others => '0'),
ALUMODE => "0000",
B => '0' & m_in.data2(50 downto 34),
BCIN => (others => '0'),
C => x"0000" & '0' & m03_p(36 downto 6),
C => 24x"0" & addend(81 downto 58),
CARRYCASCIN => '0',
CARRYIN => '0',
CARRYINSEL => "000",
@@ -414,8 +422,8 @@ begin
CECTRL => '0',
CED => '0',
CEINMODE => '0',
CEM => m_in.valid,
CEP => '0',
CEM => '0',
CEP => m_in.valid,
CLK => clk,
D => (others => '0'),
INMODE => "00000",
@@ -445,17 +453,19 @@ begin
BREG => 0,
CARRYINREG => 0,
CARRYINSELREG => 0,
CREG => 0,
INMODEREG => 0,
MREG => 1,
OPMODEREG => 0,
PREG => 0
)
port map (
A => "0000000000000" & m_in.data1(39 downto 23),
A => 6x"0" & m_in.data1(47 downto 24),
ACIN => (others => '0'),
ALUMODE => "0000",
B => "00000" & m_in.data2(63 downto 51),
BCIN => (others => '0'),
C => x"0000000" & "000" & addend(90 downto 74),
C => (others => '0'),
CARRYCASCIN => '0',
CARRYIN => '0',
CARRYINSEL => "000",
@@ -465,7 +475,7 @@ begin
CEALUMODE => '0',
CEB1 => '0',
CEB2 => '0',
CEC => '1',
CEC => '0',
CECARRYIN => '0',
CECTRL => '0',
CED => '0',
@@ -476,10 +486,9 @@ begin
D => (others => '0'),
INMODE => "00000",
MULTSIGNIN => '0',
OPMODE => "0110101",
OPMODE => "1010101",
P => m13_p,
PCIN => (others => '0'),
PCOUT => m13_pc,
PCIN => m12_pc,
RSTA => '0',
RSTALLCARRYIN => '0',
RSTALUMODE => '0',
@@ -501,12 +510,14 @@ begin
BREG => 0,
CARRYINREG => 0,
CARRYINSELREG => 0,
CREG => 0,
INMODEREG => 0,
MREG => 0,
OPMODEREG => 0,
PREG => 0
PREG => 1
)
port map (
A => "000000" & m_in.data1(63 downto 40),
A => 14x"0" & m_in.data1(63 downto 48),
ACIN => (others => '0'),
ALUMODE => "0000",
B => '0' & m_in.data2(16 downto 0),
@@ -521,20 +532,21 @@ begin
CEALUMODE => '0',
CEB1 => '0',
CEB2 => '0',
CEC => '1',
CEC => '0',
CECARRYIN => '0',
CECTRL => '0',
CED => '0',
CEINMODE => '0',
CEM => m_in.valid,
CEP => '0',
CEM => '0',
CEP => m_in.valid,
CLK => clk,
D => (others => '0'),
INMODE => "00000",
MULTSIGNIN => '0',
OPMODE => "0010101",
OPMODE => "0000101",
P => m20_p,
PCIN => m11_pc,
PCIN => (others => '0'),
PCOUT => m20_pc,
RSTA => '0',
RSTALLCARRYIN => '0',
RSTALUMODE => '0',
@@ -556,12 +568,14 @@ begin
BREG => 0,
CARRYINREG => 0,
CARRYINSELREG => 0,
CREG => 0,
INMODEREG => 0,
MREG => 1,
OPMODEREG => 0,
PREG => 0
)
port map (
A => "000000" & m_in.data1(63 downto 40),
A => 14x"0" & m_in.data1(63 downto 48),
ACIN => (others => '0'),
ALUMODE => "0000",
B => '0' & m_in.data2(33 downto 17),
@@ -576,7 +590,7 @@ begin
CEALUMODE => '0',
CEB1 => '0',
CEB2 => '0',
CEC => '1',
CEC => '0',
CECARRYIN => '0',
CECTRL => '0',
CED => '0',
@@ -587,9 +601,9 @@ begin
D => (others => '0'),
INMODE => "00000",
MULTSIGNIN => '0',
OPMODE => "0010101",
OPMODE => "1010101",
P => m21_p,
PCIN => m12_pc,
PCIN => m20_pc,
RSTA => '0',
RSTALLCARRYIN => '0',
RSTALUMODE => '0',
@@ -611,17 +625,19 @@ begin
BREG => 0,
CARRYINREG => 0,
CARRYINSELREG => 0,
CREG => 0,
INMODEREG => 0,
MREG => 0,
OPMODEREG => 0,
PREG => 0
PREG => 1
)
port map (
A => "000000" & m_in.data1(63 downto 40),
A => 14x"0" & m_in.data1(63 downto 48),
ACIN => (others => '0'),
ALUMODE => "0000",
B => '0' & m_in.data2(50 downto 34),
BCIN => (others => '0'),
C => (others => '0'),
C => "00" & addend(127 downto 82),
CARRYCASCIN => '0',
CARRYIN => '0',
CARRYINSEL => "000",
@@ -631,20 +647,21 @@ begin
CEALUMODE => '0',
CEB1 => '0',
CEB2 => '0',
CEC => '1',
CEC => '0',
CECARRYIN => '0',
CECTRL => '0',
CED => '0',
CEINMODE => '0',
CEM => m_in.valid,
CEP => '0',
CEM => '0',
CEP => m_in.valid,
CLK => clk,
D => (others => '0'),
INMODE => "00000",
MULTSIGNIN => '0',
OPMODE => "0010101",
OPMODE => "0110101",
P => m22_p,
PCIN => m13_pc,
PCIN => (others => '0'),
PCOUT => m22_pc,
RSTA => '0',
RSTALLCARRYIN => '0',
RSTALUMODE => '0',
@@ -666,17 +683,19 @@ begin
BREG => 0,
CARRYINREG => 0,
CARRYINSELREG => 0,
CREG => 0,
INMODEREG => 0,
MREG => 1,
OPMODEREG => 0,
PREG => 0
)
port map (
A => "000000" & m_in.data1(63 downto 40),
A => 14x"0" & m_in.data1(63 downto 48),
ACIN => (others => '0'),
ALUMODE => "0000",
B => "00000" & m_in.data2(63 downto 51),
BCIN => (others => '0'),
C => x"00" & "000" & addend(127 downto 91),
C => (others => '0'),
CARRYCASCIN => '0',
CARRYIN => '0',
CARRYINSEL => "000",
@@ -686,7 +705,7 @@ begin
CEALUMODE => '0',
CEB1 => '0',
CEB2 => '0',
CEC => '1',
CEC => '0',
CECARRYIN => '0',
CECTRL => '0',
CED => '0',
@@ -697,9 +716,9 @@ begin
D => (others => '0'),
INMODE => "00000",
MULTSIGNIN => '0',
OPMODE => "0110101",
OPMODE => "1010101",
P => m23_p,
PCIN => (others => '0'),
PCIN => m22_pc,
RSTA => '0',
RSTALLCARRYIN => '0',
RSTALUMODE => '0',
@@ -712,6 +731,17 @@ begin
RSTP => '0'
);
pp0 <= std_ulogic_vector(resize(signed(m13_p(37 downto 0) & m12_p(16 downto 0) &
m01_p(40 downto 0) & m00_p(16 downto 0)), 128));
pp1 <= m23_p(28 downto 0) & m22_p(16 downto 0) & m11_p(40 downto 0) & m10_p(16 downto 0) & 24x"0";
-- pp2 <= std_ulogic_vector(resize(signed(m03_p(37 downto 0) & m02_p(16 downto 0) & 34x"0"), 128));
-- pp3 <= std_ulogic_vector(resize(signed(m21_p(34 downto 0) & m20_p(16 downto 0) & 48x"0"), 128));
pp23 <= std_ulogic_vector(resize(resize(signed(m03_p(37 downto 0) & m02_p(16 downto 0) & 34x"0"), 100) +
signed(m21_p(34 downto 0) & m20_p(16 downto 0) & 48x"0"), 128));
sumlo <= std_ulogic_vector(unsigned('0' & pp0(31 downto 24)) + unsigned('0' & pp1(31 downto 24)));
s0: DSP48E1
generic map (
ACASCREG => 0,
@@ -725,16 +755,16 @@ begin
INMODEREG => 0,
MREG => 0,
OPMODEREG => 0,
PREG => 1,
PREG => 0,
USE_MULT => "none"
)
port map (
A => m22_p(5 downto 0) & x"0000" & m10_p(34 downto 27),
A => pp0(79 downto 50),
ACIN => (others => '0'),
ALUMODE => "0000",
B => m10_p(26 downto 9),
B => pp0(49 downto 32),
BCIN => (others => '0'),
C => m20_p(39 downto 0) & m02_p(5 downto 0) & "00",
C => pp1(79 downto 32),
CARRYCASCIN => '0',
CARRYIN => '0',
CARRYINSEL => "000",
@@ -751,7 +781,7 @@ begin
CED => '0',
CEINMODE => '0',
CEM => '0',
CEP => valid_1,
CEP => '0',
CLK => clk,
D => (others => '0'),
INMODE => "00000",
@@ -773,43 +803,43 @@ begin
s1: DSP48E1
generic map (
ACASCREG => 1,
ACASCREG => 0,
ALUMODEREG => 0,
AREG => 1,
BCASCREG => 1,
BREG => 1,
AREG => 0,
BCASCREG => 0,
BREG => 0,
CARRYINREG => 0,
CARRYINSELREG => 0,
CREG => 1,
CREG => 0,
INMODEREG => 0,
MREG => 0,
OPMODEREG => 0,
PREG => 0,
PREG => 1,
USE_MULT => "none"
)
port map (
A => x"000" & m22_p(41 downto 24),
A => pp0(127 downto 98),
ACIN => (others => '0'),
ALUMODE => "0000",
B => m22_p(23 downto 6),
B => pp0(97 downto 80),
BCIN => (others => '0'),
C => m23_p(36 downto 0) & x"00" & "0" & m20_p(41 downto 40),
C => pp1(127 downto 80),
CARRYCASCIN => '0',
CARRYIN => s0_carry(3),
CARRYINSEL => "000",
CEA1 => '0',
CEA2 => valid_1,
CEA2 => '0',
CEAD => '0',
CEALUMODE => '0',
CEB1 => '0',
CEB2 => valid_1,
CEC => valid_1,
CEB2 => '0',
CEC => '0',
CECARRYIN => '0',
CECTRL => '0',
CED => '0',
CEINMODE => '0',
CEM => '0',
CEP => '0',
CEP => valid_1,
CLK => clk,
D => (others => '0'),
INMODE => "00000",
@@ -829,52 +859,48 @@ begin
RSTP => '0'
);
-- mask is 0 for 32-bit ops, 0x0000ffffffff for 64-bit
p0_mask(47 downto 31) <= (others => '0');
p0_mask(30 downto 0) <= (others => not r32_1);
p0: DSP48E1
generic map (
ACASCREG => 1,
ALUMODEREG => 1,
AREG => 1,
BCASCREG => 1,
BREG => 1,
ACASCREG => 0,
ALUMODEREG => 0,
AREG => 0,
BCASCREG => 0,
BREG => 0,
CARRYINREG => 0,
CARRYINSELREG => 0,
CREG => 1,
CREG => 0,
INMODEREG => 0,
MASK => x"00007fffffff",
MREG => 0,
OPMODEREG => 0,
PREG => 0,
SEL_MASK => "C",
PREG => 1,
USE_MULT => "none",
USE_PATTERN_DETECT => "PATDET"
)
port map (
A => m21_p(22 downto 0) & m03_p(5 downto 0) & '0',
A => pp23(79 downto 50),
ACIN => (others => '0'),
ALUMODE => "00" & rnot_1 & '0',
B => (others => '0'),
B => pp23(49 downto 32),
BCIN => (others => '0'),
C => p0_mask,
C => (others => '0'),
CARRYCASCIN => '0',
CARRYIN => '0',
CARRYIN => sumlo(8),
CARRYINSEL => "000",
CARRYOUT => p0_carry,
CEA1 => '0',
CEA2 => valid_1,
CEA2 => '0',
CEAD => '0',
CEALUMODE => valid_1,
CEALUMODE => '0',
CEB1 => '0',
CEB2 => valid_1,
CEC => valid_1,
CEB2 => '0',
CEC => '0',
CECARRYIN => '0',
CECTRL => '0',
CED => '0',
CEINMODE => '0',
CEM => '0',
CEP => '0',
CEP => valid_1,
CLK => clk,
D => (others => '0'),
INMODE => "00000",
@@ -915,10 +941,10 @@ begin
USE_PATTERN_DETECT => "PATDET"
)
port map (
A => x"0000000" & '0' & m21_p(41),
A => pp23(127 downto 98),
ACIN => (others => '0'),
ALUMODE => "00" & rnot_1 & '0',
B => m21_p(40 downto 23),
B => pp23(97 downto 80),
BCIN => (others => '0'),
C => (others => '0'),
CARRYCASCIN => '0',
@@ -930,7 +956,7 @@ begin
CEALUMODE => valid_1,
CEB1 => '0',
CEB2 => valid_1,
CEC => '0',
CEC => valid_1,
CECARRYIN => '0',
CECTRL => '0',
CED => '0',
@@ -958,39 +984,26 @@ begin
RSTP => '0'
);
mult_out: process(all)
variable ov : std_ulogic;
begin
-- set overflow if the high bits are neither all zeroes nor all ones
if req_32bit = '0' then
ov := not ((p1_pat and p0_pat) or (p1_patb and p0_patb));
else
ov := not ((p1_pat and p0_pat and not product(31)) or
(p1_patb and p0_patb and product(31)));
end if;
ovf_in <= ov;
m_out.result <= product;
m_out.overflow <= overflow;
end process;
process(clk)
begin
if rising_edge(clk) then
if rnot_1 = '0' then
product(31 downto 0) <= m10_p(8 downto 0) & m01_p(5 downto 0) & m00_p(16 downto 0);
else
product(31 downto 0) <= not (m10_p(8 downto 0) & m01_p(5 downto 0) & m00_p(16 downto 0));
if valid_1 = '1' then
if rnot_1 = '0' then
product(31 downto 0) <= sumlo(7 downto 0) & pp0(23 downto 0);
else
product(31 downto 0) <= not (sumlo(7 downto 0) & pp0(23 downto 0));
end if;
end if;
m_out.valid <= valid_1;
valid_1 <= m_in.valid;
req_32bit <= r32_1;
r32_1 <= m_in.is_32bit;
rnot_1 <= m_in.not_result;
overflow <= ovf_in;
overflow <= not ((p1_pat and p0_pat) or (p1_patb and p0_patb));
end if;
end process;
m_out.result <= product;
m_out.overflow <= overflow;
end architecture behaviour;
library ieee;