rsz: stage delay implementation for the Legacy policy

[jfgava]

Summary

Stage_delay = load_delay + wire_delay

OptimizerTypes.hh — added bool use_stage_delay_ranking{false} to OptimizerRunConfig.

SetupLegacyBase.cc — rankPathDrivers() now optionally looks one step ahead in the expanded path to fetch the wire edge after each driver, computes wire_delay = arcDelay(net_edge, ...), and uses load_delay + wire_delay as the ranking key. When the flag is off, wire_delay is 0.0, so the behavior is identical to before.

Resizer.hh — added bool use_stage_delay_ranking = false (with default) to repairSetup().

Resizer.cc — accepts the new param and assigns config.use_stage_delay_ranking.

Resizer.i / Resizer-py.i — forwarded the new bool through the SWIG Tcl and Python bindings.

Resizer.tcl — added -use_stage_delay flag to define_cmd_args, parse_key_args, and the rsz::repair_setup call.

Usage: repair_timing -setup -use_stage_delay

Tests for repair_timing -use_stage_delay

C++ Unit Tests — Tier 1
File: src/rsz/test/cpp/TestSetupLegacyBase.cc

Design under test: src/rsz/test/cpp/TestSetupLegacyBase_StageDelay.v — a minimal 2-stage combinational chain (Nangate45, 2 DFF registers with a 2-inverter path in between).

Fixture: tst::IntegratedFixture (kNangate45). Placement uses compact coordinates (stage1 at origin, stage2 at 4000 dbu / 2 µm) so HPWL estimation runs without requiring SPEF.

StageDelayEqualsLoadPlusWireDelay
Verifies the core formula introduced in SetupLegacyBase::rankPathDrivers():

stage_delay[i] == load_delay[i] + wire_delay_after_driver[i]
For every driver stage on the worst-slack path to endpoint out, the test independently re-derives wire_delay by walking the STA graph edge following the gate arc and checking Edge::isWire(). Asserts stage_delay >= load_delay (wire delay is non-negative).

BothModesReturnResultsSortedDescending
Verifies the sort invariant that rankPathDrivers() guarantees for both modes: results must be in descending order by delay (primary key), with ties broken by descending path index (secondary key). Passes the same expanded path through both use_stage_delay=false and use_stage_delay=true and checks the ordering independently for each.

Tcl Integration Test — Tier 2 (PASSFAIL)
File: src/rsz/test/repair_setup_stage_delay.tcl
Golden file: src/rsz/test/repair_setup_stage_delay.ok

Smoke test that repair_timing -setup -use_stage_delay is accepted as a valid flag, the command completes without error, and produces the expected repair output.

Type of Change

• New feature

Impact

Instead of focusing just on the load_delays, now we also consider wire_delays when ranking the drivers to optimize first.

Verification

• I have verified that the local build succeeds (./etc/Build.sh).
• I have run the relevant tests and they pass.
• My code follows the repository's formatting guidelines.
• I have included tests to prevent regressions.
• I have signed my commits (DCO).

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[jfgava]

@codex review

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[maliberty]

@codex review

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Codex Review: Didn't find any major issues. Swish!

Reviewed commit: da7aaba3bb

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