Keyboard shortcuts

Press ← or → to navigate between chapters

Press S or / to search in the book

Press ? to show this help

Press Esc to hide this help

vyges-hold-fix — post-route hold-fix ECO

Part of the Vyges Loom suite (optimizer). Install once with vyges install loom, then run vyges loom hold-fix. It’s also a standalone vyges-hold-fix binary on your PATH.

The hold counterpart to the Loom optimizers. Where vyges-resize, vyges-vt-swap, and vyges-buffer-insert all fix the late / setup corner, hold violations are the opposite problem — data reaches a capture flop too early on the min-delay path — and open place-and-route flows often leave a residue of them after detailed routing. vyges-hold-fix adds delay: it inserts a delay cell in series on the net feeding each hold-violating capture pin, lifting that pin’s earliest arrival until its hold constraint is met. Each round is scored by the vyges-sta-si timer, and an insertion is kept only if the worst hold slack improved and setup stays met — so a slow clock with ample setup slack trades a little of it for hold closure, never the reverse.

Run it

vyges install loom                                       # one-time: fetch the Loom suite
vyges loom hold-fix demo                                 # instant: close a two-flop hold violation
vyges loom hold-fix run  top.holdfix -o fixed.v          # delay → hold-fixed netlist
vyges loom hold-fix run  top.holdfix --json              # before/after WHS + WNS
vyges loom hold-fix run  top.holdfix --fail-on-violation # exit 3 if hold still negative (CI gate)
vyges loom hold-fix check top.holdfix                    # validate the job

A .holdfix job is a superset of a vyges-sta-si .sta job (same design/netlist/lib/ clock or sdc/spef keys) plus the hold knobs: the buffer: (delay cell to insert), hold_margin: (target hold slack), rounds: (low/medium/high), and dont_touch:.

See the full CLI reference (generated from --help).

Where it sits

routed netlist + .lib + .spef + constraints → hold-fixed netlist + before/after WHS and WNS. A post-route ECO — with spef: present it scores the fix against real routed parasitics. It decides which capture pins to delay and how deep a chain each needs; placement + routing of the inserted cells is handed back to the flow. See the data spine.

Domain coverage

vyges-hold-fix inserts standard-cell delay/buffer cells on data paths in a gate-level netlist, scored by the digital vyges-sta-si timer — it is digital optimization. It does not apply to analog / mixed-signal blocks. For analog / MS physical & integrity verification, see lvs, layout, em-ir, thermal, and extract.

Source & releases