[oharboe]

With SYNTH_MINIMUM_KEEP_SIZE, synthesis picks the modules to keep with keep_hierarchy -min_cost, which needs a cost for every instanced blackbox. convert_liberty_areas gives Liberty cells one, but an AUTO_MEMORIES macro is a blackbox made from the RTL's own module and has none. Any AUTO_MEMORIES design with a keep threshold stopped with "Missing cost information on instanced blackbox".

Each AUTO_MEMORIES blackbox now gets the gate equivalent of the area FakeRAM writes beside its name in blackboxes.txt, <module> <area> per line, the area its .lib states. The view is not read in the module's place: its pins need not be the module's (FakeRAM names its own).

A listed module that is in the design but not a blackbox is an error: its name did not match its definition (slang's --keep-hierarchy names each elaborated module <definition>$<instance path>, and --blackboxed-module matches only the definition), so its body was elaborated into flip-flops.

asap7/riscv32i hits this once its register file is a generated macro. The integration test is The-OpenROAD-Project/bazel-orfs#1187.

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request updates flow/scripts/synth_preamble.tcl to parse the area of AUTO_MEMORIES blackboxes from their generated Liberty files and assign their gate_cost_equivalent attribute. Feedback on this change highlights that the regular expression used to parse the .lib file is fragile because it can fail on nested groups or special characters in module names, and suggests a more robust regex pattern.

[openroad-ci]

🔍 QoR check

Metrics reflect the PR merge build — i.e. what will land on the target branch.

Commit 4a1c199 · Jenkins build #5 · Baseline: build · View build on dashboard

62 design(s) checked — 0 with regression(s), 0 without a comparable baseline.

[oharboe]

@vvbandeira please retrigger, CI snag

[maliberty]

Claude:
== Priority 1 (correctness) ==

• synth_preamble.tcl:+275 question: the catch around rtlil::set_attr swallows every
  failure, not just "module not in design". If a name is mangled differently between
  extract_memories and synthesis, or set_attr -uint rejects the value, the cost is
  silently skipped and keep_hierarchy -min_cost fails later with the same opaque
  "Missing cost information" error this PR is meant to fix. Could you check the module
  exists explicitly (e.g. select -list-mod =$m returning empty) and let any other
  error propagate?
• synth_preamble.tcl:+267 suggestion: getting the area by regex over Liberty text is
  fragile. [^\x7d]*? stops at the first }, and area has no word boundary, so
  foo_area : would match. In Tcl AREs the first quantifier (\s*, greedy) sets the
  whole RE's preference, so the *? doesn't make it shortest-match the way it reads.
  It works today only because FakeRAM writes area : as the first line of the cell
  group. gen_memories.py already drives FakeRAM and knows each macro's size. Could it
  write the area next to the name (e.g. a second column in blackboxes.txt, or in
  memories.json)? That removes the regex, the hex-escaped braces, and the
  metacharacter escaping, and makes the value testable in gen_memories_test.py.
• nit: if the regex stays, add \m before area.

[oharboe]

Thanks for running Claude: your seeding of Claude gives a different result than mine, obviously. Helpful. Also, it looks like you curated the output. 😌

[oharboe]

Both done.

• The name concern is real on slang. --keep-hierarchy names each elaborated module <definition>$<instance path>, one per instance, even with no parameters, and --blackboxed-module matches only the definition. Such a module is in the design with its body elaborated, so the catch never fired: set_attr succeeded and the memory became flip-flops. Now a listed module absent from the design is skipped (slang imports a blackboxed module only where it is instanced), one present but not a blackbox is an error naming it, and set_attr is not caught. The detector fix for those names is being upstreamed separately.
• FakeRAM writes the area beside the name, <module> <area> per line in blackboxes.txt. The regex is gone, a malformed line is an error, and gen_memories_test.py checks the area against the .lib.

Merged master for #4618.

[oharboe]

The detector fix for slang's per-instance names is #4658.

b59c1d1: the cost loop missed an escaped module. yosys lists \1d_ram, blackboxes.txt has 1d_ram (read_slang's spelling), and the Tcl list lookup read \1 as an escape, so the module was skipped and keep_hierarchy -min_cost stopped with "Missing cost information on instanced blackbox \1d_ram". Checked with read_slang on a design with ram and \1d_ram: both now get their cost.

[vvbandeira]

@oharboe Thanks. This PR has merged, so a retrigger is no longer needed.