ice40: add support for both 1364.1 and LSE RAM/ROM attributes.

This commit tries to carefully follow the documented behavior of LSE
and Synplify. It will use `syn_ramstyle` attribute if there are any
write ports, and `syn_romstyle` attribute otherwise.
  * LSE supports both `syn_ramstyle` and `syn_romstyle`.
  * Synplify only supports `syn_ramstyle`, with same values as LSE.
  * Synplify also supports `syn_rw_conflict_logic`, which is not
    documented as supported for LSE.

Limitations of the Yosys implementation:
  * LSE/Synplify appear to interpret attribute values insensitive
    to case. There is currently no way to do this in Yosys (attrmap
    can only change case of attribute names).
  * LSE/Synplify support `syn_ramstyle="block_ram,no_rw_check"`
    syntax to turn off insertion of transparency logic. There is
    currently no way to support multiple valued attributes in
    memory_bram. It is also not clear if that is a good idea, since
    it can cause sim/synth mismatches.
  * LSE/Synplify/1364.1 support block ROM inference from full case
    statements. Yosys does not currently perform this transformation.
  * LSE/Synplify propagate `syn_ramstyle`/`syn_romstyle` attributes
    from the module to the inner memories. There is currently no way
    to do this in Yosys (attrmvcp only works on cells and wires).

1 files changed, 126 insertions, 0 deletions

diff --git a/tests/arch/ice40/memories.ys b/tests/arch/ice40/memories.ys
new file mode 100644
index 000000000..83386f0ec
--- /dev/null
+++ b/tests/arch/ice40/memories.ys
@@ -0,0 +1,126 @@
+# RAM bits <= 4K; Data width <= 16; Address width <= 11: -> SB_RAM40_4K
+
+design -reset; read_verilog ../common/blockram.v
+chparam -set ADDRESS_WIDTH 11 -set DATA_WIDTH 2 sync_ram_sdp
+synth_ice40 -top sync_ram_sdp; cd sync_ram_sdp
+select -assert-count 1 t:SB_RAM40_4K
+
+design -reset; read_verilog ../common/blockram.v
+chparam -set ADDRESS_WIDTH 10 -set DATA_WIDTH 4 sync_ram_sdp
+synth_ice40 -top sync_ram_sdp; cd sync_ram_sdp
+select -assert-count 1 t:SB_RAM40_4K
+
+design -reset; read_verilog ../common/blockram.v
+chparam -set ADDRESS_WIDTH 9 -set DATA_WIDTH 8 sync_ram_sdp
+synth_ice40 -top sync_ram_sdp; cd sync_ram_sdp
+select -assert-count 1 t:SB_RAM40_4K
+
+design -reset; read_verilog ../common/blockram.v
+chparam -set ADDRESS_WIDTH 8 -set DATA_WIDTH 16 sync_ram_sdp
+synth_ice40 -top sync_ram_sdp; cd sync_ram_sdp
+select -assert-count 1 t:SB_RAM40_4K
+
+## With parameters
+
+design -reset; read_verilog ../common/blockram.v
+chparam -set ADDRESS_WIDTH 2 -set DATA_WIDTH 8 sync_ram_sdp
+synth_ice40 -top sync_ram_sdp; cd sync_ram_sdp
+select -assert-count 0 t:SB_RAM40_4K # too inefficient
+select -assert-min 1 t:SB_DFFE
+
+design -reset; read_verilog ../common/blockram.v
+chparam -set ADDRESS_WIDTH 2 -set DATA_WIDTH 8 sync_ram_sdp
+setattr -set syn_ramstyle "block_ram" m:memory
+synth_ice40 -top sync_ram_sdp; cd sync_ram_sdp
+select -assert-count 1 t:SB_RAM40_4K
+
+design -reset; read_verilog ../common/blockram.v
+chparam -set ADDRESS_WIDTH 2 -set DATA_WIDTH 8 sync_ram_sdp
+setattr -set ram_block 1 m:memory
+synth_ice40 -top sync_ram_sdp; cd sync_ram_sdp
+select -assert-count 1 t:SB_RAM40_4K
+
+design -reset; read_verilog ../common/blockram.v
+chparam -set ADDRESS_WIDTH 2 -set DATA_WIDTH 8 sync_ram_sdp
+setattr -set logic_block 1 m:memory
+synth_ice40 -top sync_ram_sdp; cd sync_ram_sdp
+select -assert-count 0 t:SB_RAM40_4K # requested FFRAM explicitly
+select -assert-min 1 t:SB_DFFE
+
+design -reset; read_verilog ../common/blockram.v
+chparam -set ADDRESS_WIDTH 2 -set DATA_WIDTH 8 sync_ram_sdp
+setattr -set syn_romstyle "ebr" m:memory
+synth_ice40 -top sync_ram_sdp; cd sync_ram_sdp
+select -assert-count 0 t:SB_RAM40_4K # requested BROM but this is a RAM
+select -assert-min 1 t:SB_DFFE
+
+design -reset; read_verilog ../common/blockram.v
+chparam -set ADDRESS_WIDTH 2 -set DATA_WIDTH 8 sync_ram_sdp
+setattr -set rom_block 1 m:memory
+synth_ice40 -top sync_ram_sdp; cd sync_ram_sdp
+select -assert-count 0 t:SB_RAM40_4K # requested BROM but this is a RAM
+select -assert-min 1 t:SB_DFFE
+
+# ROM bits <= 4K; Data width <= 16; Address width <= 11: -> SB_RAM40_4K
+
+design -reset; read_verilog ../common/blockrom.v
+chparam -set ADDRESS_WIDTH 11 -set DATA_WIDTH 2 sync_rom
+synth_ice40 -top sync_rom; cd sync_rom
+select -assert-count 1 t:SB_RAM40_4K
+
+design -reset; read_verilog ../common/blockrom.v
+chparam -set ADDRESS_WIDTH 10 -set DATA_WIDTH 4 sync_rom
+synth_ice40 -top sync_rom; cd sync_rom
+select -assert-count 1 t:SB_RAM40_4K
+
+design -reset; read_verilog ../common/blockrom.v
+chparam -set ADDRESS_WIDTH 9 -set DATA_WIDTH 8 sync_rom
+synth_ice40 -top sync_rom; cd sync_rom
+select -assert-count 1 t:SB_RAM40_4K
+
+design -reset; read_verilog ../common/blockrom.v
+chparam -set ADDRESS_WIDTH 8 -set DATA_WIDTH 16 sync_rom
+synth_ice40 -top sync_rom; cd sync_rom
+select -assert-count 1 t:SB_RAM40_4K
+
+## With parameters
+
+design -reset; read_verilog ../common/blockrom.v
+chparam -set ADDRESS_WIDTH 2 -set DATA_WIDTH 8 sync_rom
+write_ilang
+synth_ice40 -top sync_rom; cd sync_rom
+select -assert-count 0 t:SB_RAM40_4K # too inefficient
+select -assert-min 1 t:SB_LUT4
+
+design -reset; read_verilog ../common/blockrom.v
+chparam -set ADDRESS_WIDTH 2 -set DATA_WIDTH 8 sync_rom
+setattr -set syn_romstyle "ebr" m:memory
+synth_ice40 -top sync_rom; cd sync_rom
+select -assert-count 1 t:SB_RAM40_4K
+
+design -reset; read_verilog ../common/blockrom.v
+chparam -set ADDRESS_WIDTH 2 -set DATA_WIDTH 8 sync_rom
+setattr -set rom_block 1 m:memory
+synth_ice40 -top sync_rom; cd sync_rom
+select -assert-count 1 t:SB_RAM40_4K
+
+design -reset; read_verilog ../common/blockrom.v
+chparam -set ADDRESS_WIDTH 2 -set DATA_WIDTH 8 sync_rom
+setattr -set logic_block 1 m:memory
+synth_ice40 -top sync_rom; cd sync_rom
+select -assert-count 0 t:SB_RAM40_4K # requested LUTROM explicitly
+select -assert-min 1 t:SB_LUT4
+
+design -reset; read_verilog ../common/blockrom.v
+chparam -set ADDRESS_WIDTH 2 -set DATA_WIDTH 8 sync_rom
+setattr -set syn_ramstyle "block_ram" m:memory
+synth_ice40 -top sync_rom; cd sync_rom
+select -assert-count 0 t:SB_RAM40_4K # requested BRAM but this is a ROM
+select -assert-min 1 t:SB_LUT4
+
+design -reset; read_verilog ../common/blockrom.v
+chparam -set ADDRESS_WIDTH 2 -set DATA_WIDTH 8 sync_rom
+setattr -set ram_block 1 m:memory
+synth_ice40 -top sync_rom; cd sync_rom
+select -assert-count 0 t:SB_RAM40_4K # requested BRAM but this is a ROM
+select -assert-min 1 t:SB_LUT4