tinyRocket: the asap7 design builds again, its cache memories modelled

[oharboe]

asap7/tinyRocket, ORFS's AUTO_MEMORIES design, builds again. It now serves as the fast-turnaround case for register files built through yosys's memlib + techmap, which come next and separately.

Why it was broken, and why nobody saw it

The Rocket Chip generator leaves its cache memories as black boxes: data_arrays_0_ext, data_arrays_0_0_ext and tag_array_ext. The generic tinyRocket sources define none of them.

• nangate45 maps them onto hand-made fakeram macros in a platform file.
• asap7 relied on AUTO_MEMORIES, which only detects a memory yosys infers as $mem_v2. Only tag_array got a macro, because a .memories override forced it. The two data arrays went undetected, and canonicalization stopped:

  ERROR: Module `\data_arrays_0_ext' referenced in module `\data_arrays_0' in cell `\data_arrays_0_ext' is not part of the design.
  

  Under slang, the default here since a851e62, memory extraction stopped earlier on the same unknown modules. The flow printed only "Compilation failed".

Nothing built the design:

• ORFS CI builds tinyRocket on nangate45 only.
• Here, auto_memories_outputs_test analyses tinyRocket's synthesis without running it.

The fix

ORFS patch 0092, carried and not upstreamed:

• designs/asap7/tinyRocket/memories.v has behavioural models of the three memories in firtool's read-write convention, with the read address registered as firtool writes it. yosys then infers each one as a clocked-read memory, and AUTO_MEMORIES decides:

  memory	words × bits	result
  data_arrays_0_ext	64 × 32, 4 mask lanes	FakeRAM macro
  data_arrays_0_0_ext	64 × 32	FakeRAM macro
  tag_array_ext	4 × 25	flip-flops (below the depth floor of 16)
  Rocket._T_288, the integer register file	31 × 32, 2R1W	flip-flops, unchanged

• tag_array.memories is deleted. With a behavioural model, the gate's own choice stands. The docs' override example no longer names it. schema_test's tag_array case, whose fixture it was, goes too; test_merge_new_entry_taken_whole still covers an override taken whole.

Patch 0092 skips 0089–0091, which #1187 uses.

In bazel-orfs

//test:tinyrocket_synth_build_test builds the synthesis, AUTO_MEMORIES detection and macro generation included. It is not manual, so CI runs it.

Tested

	result
//test:tinyrocket_synth_build_test, //test:auto_memories_outputs_test, //test:no_auto_memories_outputs_test	pass
tinyRocket to global route	floorplan through global route in 158 s; 2 macros placed; minimum-period estimate 1 243 ps on the 1 600 ps clock; 3 956 µm² at 41 %
ORFS schema_test.py	6 tests pass
fix_lint, public_surface, host_tools	pass

🤖 Generated with Claude Code