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execute1: Use truth table embedded in instruction for CR logical ops

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It turns out that CR logical instructions have the truth table of
the operation embedded in the instruction word.  This means that we
can collect the two input operand bits into a 2-bit value and use
that as the index to select the appropriate bit from the instruction
word.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
jtag-port
Paul Mackerras 5 years ago
parent a2bf039a70
commit 441160d865
1 changed files with 5 additions and 21 deletions
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26
execute1.vhdl
Unescape Escape View File

@ -200,6 +200,7 @@ begin
variable bo, bi : std_ulogic_vector(4 downto 0); variable bo, bi : std_ulogic_vector(4 downto 0);
variable bf, bfa : std_ulogic_vector(2 downto 0); variable bf, bfa : std_ulogic_vector(2 downto 0);
variable cr_op : std_ulogic_vector(9 downto 0); variable cr_op : std_ulogic_vector(9 downto 0);
variable cr_operands : std_ulogic_vector(1 downto 0);
variable bt, ba, bb : std_ulogic_vector(4 downto 0); variable bt, ba, bb : std_ulogic_vector(4 downto 0);
variable btnum, banum, bbnum : integer range 0 to 31; variable btnum, banum, bbnum : integer range 0 to 31;
variable crresult : std_ulogic; variable crresult : std_ulogic;
@ -532,27 +533,10 @@ begin
btnum := 31 - to_integer(unsigned(bt)); btnum := 31 - to_integer(unsigned(bt));
banum := 31 - to_integer(unsigned(ba)); banum := 31 - to_integer(unsigned(ba));
bbnum := 31 - to_integer(unsigned(bb)); bbnum := 31 - to_integer(unsigned(bb));
case cr_op(8 downto 5) is -- Bits 5-8 of cr_op give the truth table of the requested
when "1001" => -- CREQV -- logical operation
crresult := not(e_in.cr(banum) xor e_in.cr(bbnum)); cr_operands := e_in.cr(banum) & e_in.cr(bbnum);
when "0111" => -- CRNAND crresult := cr_op(5 + to_integer(unsigned(cr_operands)));
crresult := not(e_in.cr(banum) and e_in.cr(bbnum));
when "0100" => -- CRANDC
crresult := (e_in.cr(banum) and not e_in.cr(bbnum));
when "1000" => -- CRAND
crresult := (e_in.cr(banum) and e_in.cr(bbnum));
when "0001" => -- CRNOR
crresult := not(e_in.cr(banum) or e_in.cr(bbnum));
when "1101" => -- CRORC
crresult := (e_in.cr(banum) or not e_in.cr(bbnum));
when "0110" => -- CRXOR
crresult := (e_in.cr(banum) xor e_in.cr(bbnum));
when "1110" => -- CROR
crresult := (e_in.cr(banum) or e_in.cr(bbnum));
when others =>
crresult := '0';
report "BAD CR?";
end case;
v.e.write_cr_mask := num_to_fxm((31-btnum) / 4); v.e.write_cr_mask := num_to_fxm((31-btnum) / 4);
for i in 0 to 31 loop for i in 0 to 31 loop
if i = btnum then if i = btnum then

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