yosys/docs/source/code_examples/fifo/fifo.libmap

yosys> debug memory_libmap -lib +/ice40/brams.txt -lib +/ice40/spram.txt -no-auto-huge

yosys> memory_libmap -lib +/ice40/brams.txt -lib +/ice40/spram.txt -no-auto-huge

4. Executing MEMORY_LIBMAP pass (mapping memories to cells).
Memory fifo.data mapping candidates (post-geometry):
- logic fallback
  - cost: 2048.000000
- $__ICE40_RAM4K_:
  - option HAS_BE 0
  - emulation score: 7
  - replicates (for ports): 1
  - replicates (for data): 1
  - mux score: 0
  - demux score: 0
  - cost: 78.000000
  - abits 11 dbits 2 4 8 16
  - chosen base width 8
  - swizzle 0 1 2 3 4 5 6 7
  - emulate read-first behavior
  - write port 0: port group W
    - widths 2 4 8
  - read port 0: port group R
    - widths 2 4 8 16
    - emulate transparency with write port 0
- $__ICE40_RAM4K_:
  - option HAS_BE 1
  - emulation score: 7
  - replicates (for ports): 1
  - replicates (for data): 1
  - mux score: 0
  - demux score: 0
  - cost: 78.000000
  - abits 11 dbits 2 4 8 16
  - byte width 1
  - chosen base width 8
  - swizzle 0 1 2 3 4 5 6 7
  - emulate read-first behavior
  - write port 0: port group W
    - widths 16
  - read port 0: port group R
    - widths 2 4 8 16
    - emulate transparency with write port 0
Memory fifo.data mapping candidates (after post-geometry prune):
- logic fallback
  - cost: 2048.000000
- $__ICE40_RAM4K_:
  - option HAS_BE 0
  - emulation score: 7
  - replicates (for ports): 1
  - replicates (for data): 1
  - mux score: 0
  - demux score: 0
  - cost: 78.000000
  - abits 11 dbits 2 4 8 16
  - chosen base width 8
  - swizzle 0 1 2 3 4 5 6 7
  - emulate read-first behavior
  - write port 0: port group W
    - widths 2 4 8
  - read port 0: port group R
    - widths 2 4 8 16
    - emulate transparency with write port 0
mapping memory fifo.data via $__ICE40_RAM4K_