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https://github.com/antonblanchard/microwatt.git
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39ca675ce3
This adds logic to do basic decoding of the prefixed instructions defined in PowerISA v3.1B which are in the SFFS (Scalar Fixed plus Floating-Point Subset) compliancy subset. In PowerISA v3.1B SFFS, there are 14 prefixed load/store instructions plus the prefixed no-op instruction (pnop). The prefixed load/store instructions all use an extended version of D-form, which has an extra 18 bits of displacement in the prefix, plus an 'R' bit which enables PC-relative addressing. When decode1 sees an instruction word where the insn_code is INSN_prefix (i.e. the primary opcode was 1), it stores the prefix word and sends nothing down to decode2 in that cycle. When the next valid instruction word arrives, it is interpreted as a suffix, meaning that its insn_code gets modified before being used to look up the decode table. The insn_code values are rearranged so that the values for instructions which are the suffix of a valid prefixed instruction are all at even indexes, and the corresponding prefixed instructions follow immediately, so that an insn_code value can be converted to the corresponding prefixed value by setting the LSB of the insn_code value. There are two prefixed instructions, pld and pstd, for which the suffix is not a valid SFFS instruction by itself, so these have been given dummy insn_code values which decode as illegal (INSN_op57 and INSN_op61). For a prefixed instruction, decode1 examines the type and subtype fields of the prefix and checks that the suffix is valid for the type and subtype. This check doesn't affect which entry of the decode table is used; the result is passed down to decode2, and will in future be acted upon in execute1. The instruction address passed down to decode2 is the address of the prefix. To enable this, part of the instruction address is saved when the prefix is seen, and then the instruction address received from icache is partly overlaid by the saved prefix address. Because prefixed instructions are not permitted to cross 64-byte boundaries, we only need to save bits 5:2 of the instruction to do this. If the alignment restriction ever gets relaxed, we will then need to save more bits of the address. Decode2 has been extended to handle the R bit of the prefix (in 8LS and MLS forms) and to be able to generate the 34-bit immediate value from the prefix and suffix. Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
269 lines
9.2 KiB
VHDL
269 lines
9.2 KiB
VHDL
library ieee;
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use ieee.std_logic_1164.all;
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package insn_helpers is
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function insn_rs (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_rt (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_ra (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_rb (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_rcreg (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_si (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_ui (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_l (insn_in : std_ulogic_vector) return std_ulogic;
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function insn_sh32 (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_mb32 (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_me32 (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_li (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_lk (insn_in : std_ulogic_vector) return std_ulogic;
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function insn_aa (insn_in : std_ulogic_vector) return std_ulogic;
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function insn_rc (insn_in : std_ulogic_vector) return std_ulogic;
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function insn_oe (insn_in : std_ulogic_vector) return std_ulogic;
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function insn_bd (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_bf (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_bfa (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_cr (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_bt (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_ba (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_bb (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_fxm (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_bo (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_bi (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_bh (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_d (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_ds (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_dq (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_dx (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_to (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_bc (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_sh (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_me (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_mb (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_frt (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_fra (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_frb (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_frc (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_u (insn_in : std_ulogic_vector) return std_ulogic_vector;
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function insn_prefix_r(prefix : std_ulogic_vector) return std_ulogic;
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function insn_prefixed_si(prefix : std_ulogic_vector; suffix : std_ulogic_vector)
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return std_ulogic_vector;
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end package insn_helpers;
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package body insn_helpers is
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function insn_rs (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(25 downto 21);
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end;
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function insn_rt (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(25 downto 21);
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end;
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function insn_ra (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(20 downto 16);
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end;
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function insn_rb (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(15 downto 11);
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end;
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function insn_rcreg (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(10 downto 6);
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end;
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function insn_si (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(15 downto 0);
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end;
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function insn_ui (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(15 downto 0);
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end;
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function insn_l (insn_in : std_ulogic_vector) return std_ulogic is
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begin
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return insn_in(21);
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end;
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function insn_sh32 (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(15 downto 11);
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end;
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function insn_mb32 (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(10 downto 6);
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end;
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function insn_me32 (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(5 downto 1);
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end;
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function insn_li (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(25 downto 2);
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end;
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function insn_lk (insn_in : std_ulogic_vector) return std_ulogic is
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begin
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return insn_in(0);
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end;
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function insn_aa (insn_in : std_ulogic_vector) return std_ulogic is
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begin
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return insn_in(1);
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end;
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function insn_rc (insn_in : std_ulogic_vector) return std_ulogic is
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begin
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return insn_in(0);
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end;
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function insn_oe (insn_in : std_ulogic_vector) return std_ulogic is
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begin
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return insn_in(10);
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end;
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function insn_bd (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(15 downto 2);
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end;
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function insn_bf (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(25 downto 23);
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end;
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function insn_bfa (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(20 downto 18);
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end;
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function insn_cr (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(10 downto 1);
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end;
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function insn_bb (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(15 downto 11);
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end;
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function insn_ba (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(20 downto 16);
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end;
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function insn_bt (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(25 downto 21);
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end;
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function insn_fxm (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(19 downto 12);
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end;
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function insn_bo (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(25 downto 21);
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end;
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function insn_bi (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(20 downto 16);
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end;
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function insn_bh (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(12 downto 11);
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end;
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function insn_d (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(15 downto 0);
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end;
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function insn_ds (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(15 downto 2);
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end;
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function insn_dq (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(15 downto 4);
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end;
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function insn_dx (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(15 downto 6) & insn_in(20 downto 16) & insn_in(0);
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end;
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function insn_to (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(25 downto 21);
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end;
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function insn_bc (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(10 downto 6);
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end;
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function insn_sh (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(1) & insn_in(15 downto 11);
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end;
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function insn_me (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(5) & insn_in(10 downto 6);
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end;
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function insn_mb (insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(5) & insn_in(10 downto 6);
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end;
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function insn_frt(insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(25 downto 21);
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end;
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function insn_fra(insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(20 downto 16);
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end;
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function insn_frb(insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(15 downto 11);
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end;
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function insn_frc(insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(10 downto 6);
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end;
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function insn_u(insn_in : std_ulogic_vector) return std_ulogic_vector is
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begin
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return insn_in(15 downto 12);
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end;
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function insn_prefix_r(prefix : std_ulogic_vector) return std_ulogic is
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begin
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return prefix(20);
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end;
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function insn_prefixed_si(prefix : std_ulogic_vector; suffix : std_ulogic_vector)
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return std_ulogic_vector is
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begin
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return prefix(17 downto 0) & suffix(15 downto 0);
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end;
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end package body insn_helpers;
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