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374f4c536d
This adds code to writeback to format data and test the result against zero for the purpose of setting CR0. The data formatter is able to shift and mask by bytes and do byte reversal and sign extension. It can also put together bytes from two input doublewords to support unaligned loads (including unaligned byte-reversed loads). The data formatter starts with an 8:1 multiplexer that is able to direct any byte of the input to any byte of the output. This lets us rotate the data and simultaneously byte-reverse it. The rotated/reversed data goes to a register for the unaligned cases that overlap two doublewords. Then there is per-byte logic that does trimming, sign extension, and splicing together bytes from a previous input doubleword (stored in data_latched) and the current doubleword. Finally the 64-bit result is tested to set CR0 if rc = 1. This removes the RC logic from the execute2, multiply and divide units, and the shift/mask/byte-reverse/sign-extend logic from loadstore2. Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
51 lines
1.1 KiB
VHDL
51 lines
1.1 KiB
VHDL
library ieee;
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use ieee.std_logic_1164.all;
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use ieee.numeric_std.all;
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library work;
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use work.common.all;
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-- 2 cycle ALU
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-- We handle rc form instructions here
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entity execute2 is
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port (
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clk : in std_ulogic;
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e_in : in Execute1ToExecute2Type;
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e_out : out Execute2ToWritebackType
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);
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end execute2;
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architecture behave of execute2 is
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signal r, rin : Execute2ToWritebackType;
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begin
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execute2_0: process(clk)
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begin
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if rising_edge(clk) then
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r <= rin;
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end if;
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end process;
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execute2_1: process(all)
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variable v : Execute2ToWritebackType;
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begin
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v := rin;
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v.valid := e_in.valid;
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v.write_enable := e_in.write_enable;
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v.write_reg := e_in.write_reg;
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v.write_data := e_in.write_data;
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v.write_cr_enable := e_in.write_cr_enable;
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v.write_cr_mask := e_in.write_cr_mask;
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v.write_cr_data := e_in.write_cr_data;
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v.rc := e_in.rc;
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-- Update registers
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rin <= v;
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-- Update outputs
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e_out <= r;
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end process;
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end;
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