global_route.tcl: carry -allow_congestion into the incremental reroutes

[oharboe]

Draft: depends on The-OpenROAD-Project/OpenROAD#11525. It stays a draft until that PR is merged and ORFS's OpenROAD is bumped past it. On today's OpenROAD it fails later in the same stage (EST-0005 after repair_antennas, see the table).

A flow that accepts congestion says so once, with -allow_congestion in GLOBAL_ROUTE_ARGS, but every global_route call decides for itself. The -start_incremental/-end_incremental brackets around repair_design, repair_timing and recover_power ran without the flag. So the reroute after repair_design treated the accepted congested route as unaccepted, rerouted it harder, and failed on GRT-0232. This PR passes the flow's choice to every bracket.

Tested locally

The grt stage of a small design, with the route congested on purpose: a PRE_GLOBAL_ROUTE_TCL sets set_global_routing_layer_adjustment M2-M7 0.97. It is accepted with GLOBAL_ROUTE_ARGS=-congestion_iterations 0 -allow_congestion -verbose, with incremental repair and antenna repair on. Both OpenROAD binaries are built from the same master commit, with and without #11525.

OpenROAD \ global_route.tcl	master	this PR
master	GRT-0232 at the first -end_incremental	EST-0005 after repair_antennas
with #11525	GRT-0232 at the first -end_incremental	finishes: route, both repairs, antennas, parasitics

Each change is needed:

• This PR: the incremental reroutes decide from their own call.
• #11525: repair_antennas no longer withdraws the accepted route that estimate_parasitics needs.

No ORFS design routes with -allow_congestion today, which is why CI has not seen either failure.

tclfmt and tclint are clean.

[gemini-code-assist]

Code Review

This pull request updates the global routing flow to conditionally include the -allow_congestion flag based on the GLOBAL_ROUTE_ARGS environment variable. The reviewer suggests using the existing env_var_exists_and_non_empty helper function to make the environment variable check more robust and prevent potential runtime errors.

[openroad-ci]

🔍 QoR check

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

Commit 985039d · Jenkins build #4 · Baseline: build · View build on dashboard

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

[eder-matheus]

@oharboe repair_antennas also needs the {*}$allow_congestion flag to be consistent with the other calls.

[oharboe]

@maliberty @eder-matheus ORFS origin/master went red due to a rules-base.json update needed after tools/OpenROAD update, nothing to do on this PR.

[eder-matheus]

@maliberty @eder-matheus ORFS origin/master went red due to a rules-base.json update needed after tools/OpenROAD update, nothing to do on this PR.

I've restarted the pipeline, I believe it will get the correct metric limits now. If it still doesn't work, could you merge latest master on your branch?