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loadstore1: Simplify address generation in OP_FETCH_FAILED case

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Instead of having a multiplexer in loadstore1 in order to be able to
put the instruction address into v.addr, we now set decode.input_reg_a
to CIA in the decode table entry for OP_FETCH_FAILED.  That means that
the operand selection machinery in decode2 will supply the instruction
address to loadstore1 on the lv.addr1 input and no special case is
needed in loadstore1.  This saves a few LUTs (~40 on the Artix-7).

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
This commit is contained in:
Paul Mackerras
2022-07-29 08:27:10 +10:00
parent 795b6e2a6b
commit 7a60c118ed
4 changed files with 2 additions and 5 deletions
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3
common.vhdl
View File

@@ -476,7 +476,6 @@ package common is
type Execute1ToLoadstore1Type is record
valid : std_ulogic;
op : insn_type_t; -- what ld/st or m[tf]spr or TLB op to do
nia : std_ulogic_vector(63 downto 0);
insn : std_ulogic_vector(31 downto 0);
instr_tag : instr_tag_t;
addr1 : std_ulogic_vector(63 downto 0);
@@ -504,7 +503,7 @@ package common is
(valid => '0', op => OP_ILLEGAL, ci => '0', byte_reverse => '0',
sign_extend => '0', update => '0', xerc => xerc_init,
reserve => '0', rc => '0', virt_mode => '0', priv_mode => '0',
nia => (others => '0'), insn => (others => '0'),
insn => (others => '0'),
instr_tag => instr_tag_init,
addr1 => (others => '0'), addr2 => (others => '0'), data => (others => '0'),
write_reg => (others => '0'),

2
decode1.vhdl
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@@ -527,7 +527,7 @@ architecture behaviour of decode1 is
-- unit fac internal in1 in2 in3 out CR CR inv inv cry cry ldst BR sgn upd rsrv 32b sgn rc lk sgl rpt
-- op in out A out in out len ext pipe
constant nop_instr : decode_rom_t := (ALU, NONE, OP_NOP, NONE, NONE, NONE, NONE, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0', '0', NONE);
constant fetch_fail_inst: decode_rom_t := (LDST, NONE, OP_FETCH_FAILED, NONE, NONE, NONE, NONE, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0', '0', NONE);
constant fetch_fail_inst: decode_rom_t := (LDST, NONE, OP_FETCH_FAILED, CIA, NONE, NONE, NONE, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0', '0', NONE);
function decode_ram_spr(sprn : spr_num_t) return ram_spr_info is
variable ret : ram_spr_info;

1
execute1.vhdl
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@@ -1554,7 +1554,6 @@ begin
-- Outputs to loadstore1 (async)
lv.op := e_in.insn_type;
lv.nia := e_in.nia;
lv.instr_tag := e_in.instr_tag;
lv.addr1 := a_in;
lv.addr2 := b_in;

1
loadstore1.vhdl
View File

@@ -497,7 +497,6 @@ begin
when OP_FETCH_FAILED =>
-- send it to the MMU to do the radix walk
v.instr_fault := '1';
v.addr := l_in.nia;
v.mmu_op := '1';
when others =>
end case;