[jhkim-pii]

Summary

• Adds flow knobs for a lowest-VT-only flow (LOWEST_VT_ONLY) and for power recovery with repair_power (REPAIR_POWER, REPAIR_POWER_VT_BUDGET).

Why this PR is needed

• Use case: A design team wants the best timing first, so the flow should build and repair the design with the lowest (fastest) VT only, and then move the cells that have slack back to the higher VTs to save power.
• Today: This takes a hand-written dont use list in the design config and a Tcl hook that lifts the list before the power recovery and restores it after.
• With this PR: The platform lists the cells of the other VTs once, and a design turns the flow on with one variable.

Problem

• No flow variable selects the VTs a design may use, and repair_power is not called by the flow.

# Before: per design, by hand
export DONT_USE_CELLS += <every cell of the other VTs>
export POST_GLOBAL_ROUTE_TCL = <hook: reset_dont_use, set_dont_use, repair_power, restore>

Changes

Area	Before	After
Dont use list	DONT_USE_CELLS only	dont_use_cells in util.tcl: DONT_USE_CELLS plus NON_LOWEST_VT_CELLS when LOWEST_VT_ONLY=1; used by the seven set_dont_use and ABC -dont_use sites
Power recovery after the global route repair	RECOVER_POWER (repair_timing -recover_power)	Also REPAIR_POWER=1: repair_power inside an incremental global route; with LOWEST_VT_ONLY the higher VTs are lifted before it and restored after
VT budget	None	REPAIR_POWER_VT_BUDGET is passed as repair_power -vt_budget
Platforms	No VT cell list	NON_LOWEST_VT_CELLS ?= in asap7 (from ASAP7_USE_VT) and gt2n (from GT2N_USE_VT); empty on single-VT platforms

flowchart LR
  A[Synthesis] --> B[Floorplan, place, CTS] --> C[Global route + timing repair] --> D[repair_power] --> E[Detailed route]
  A -. lowest VT only .- C
  D -. every VT usable .- D

Loading

UI Changes

# design config.mk
export LOWEST_VT_ONLY = 1
export REPAIR_POWER = 1
export REPAIR_POWER_VT_BUDGET = *_ASAP7_75t_SL 50   # optional

Variable	Default	Meaning
LOWEST_VT_ONLY	0	Add NON_LOWEST_VT_CELLS to the dont use cells from synthesis to the global route timing repair
NON_LOWEST_VT_CELLS	empty	Cell patterns of every VT but the lowest; set by the platform
REPAIR_POWER	0	Run repair_power after the global route timing repair
REPAIR_POWER_VT_BUDGET	unset	-vt_budget of repair_power: pairs of cell patterns and a percent

Impact

• All knobs are off by default; flows that do not set them run the same commands as before.
• On a single-VT platform LOWEST_VT_ONLY=1 changes nothing, since NON_LOWEST_VT_CELLS is empty.
• Dependency: repair_power and the VT swap fixes for dont use changes are OpenROAD changes that are not in tools/OpenROAD yet. This PR does not bump the submodule, so REPAIR_POWER = 1 fails until they land. The default flow is not affected.

Details

Flow

• Synthesis: Both the Yosys/ABC path and the OpenROAD synthesis path take the same list from dont_use_cells.
• Floorplan to global route repair: set_dont_use [dont_use_cells].
• Power recovery: repair_power_helper runs reset_dont_use, set_dont_use with DONT_USE_CELLS only, repair_power -verbose [-setup_margin] [-vt_budget], then restores the full list. SETUP_SLACK_MARGIN is passed when it is not 0.
• Clock buffers: CTS_BUF_LIST is not changed by the knobs.

Testing

• Run locally with an OpenROAD build that has repair_power and the VT swap fixes.
• asap7 gcd with ASAP7_USE_VT = RVT LVT SLVT, LOWEST_VT_ONLY = 1, REPAIR_POWER = 1 (local config, not in this PR): Completes; the synthesized netlist is SLVT only (304 cells, 0 RVT, 0 LVT); repair_power brings SLVT from 100% to 4.3% of the logic cells (budget 50%) and total power from 711 to 603 uW; final setup WS +5.4 ps, no slew or capacitance violation.
• Knobs through a private multi-VT platform: The four combinations (off, REPAIR_POWER, LOWEST_VT_ONLY + REPAIR_POWER, plus a VT budget) give the same final metrics as the hand-written hook flow.
• Knobs off: The same design gives identical final metrics on this branch and on master.
• tclfmt, tclint, yamlfix and generate-variables-docs.py pass.

[gemini-code-assist]

Code Review

This pull request introduces support for a lowest-VT-only flow (LOWEST_VT_ONLY) in OpenROAD-flow-scripts, allowing synthesis, placement, and timing repair using only the fastest VT cells, followed by power recovery (REPAIR_POWER) after global routing. It also updates the metadata upload script (uploadMetadata.py) and its tests to parse and report detailed flow outcomes (such as timeouts, crashes, and errors) from stage logs. All provided review comments were filtered out as they suggested one-off encoding cleanups, which is discouraged by the repository's style guide. Consequently, there is no additional feedback to provide.

[openroad-ci]

🔍 QoR check

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

Commit b353340 · Jenkins build #1 · Baseline: build · View build on dashboard

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