synth: Add sort before ABC to avoid nondeterminism (workaround)#4058
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openroad-ci wants to merge 8 commits intoThe-OpenROAD-Project:masterfrom
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synth: Add sort before ABC to avoid nondeterminism (workaround)#4058openroad-ci wants to merge 8 commits intoThe-OpenROAD-Project:masterfrom
openroad-ci wants to merge 8 commits intoThe-OpenROAD-Project:masterfrom
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Insert a `sort` command before abc execution in synth.tcl to stabilize module iteration order. Without this, abc_new visits modules in dict insertion order which can vary between runs, producing different netlists from the same RTL input. The sort is enabled by default and can be disabled by setting SYNTH_SORT_BEFORE_ABC=-1. Closes The-OpenROAD-Project#4056 Signed-off-by: Jaehyun Kim <jhkim@precisioninno.com>
oharboe
reviewed
Mar 26, 2026
flow/scripts/synth.tcl
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| # 2025-03-26: Temporary workaround before yosys fix. | ||
| # Sort design objects before abc execution to avoid non-deterministic result. | ||
| # Enabled by default and can be disabled with SYNTH_SORT_BEFORE_ABC=-1. | ||
| if { ![env_var_equals SYNTH_SORT_BEFORE_ABC -1] } { |
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add to variables.yaml and use POLA 0/1 as boolean and 0 default
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@oharboe
Oops. Weird value '-1' was there. I'll fix it.
By the way, I intended to make the sorting on-by-default to avoid the ND issue. The sorting runtime is trivial.
Please let me know if you disagree to the sorting on-by-default.
Address review feedback: use standard ORFS 0/1 boolean convention with $::env() instead of env_var_equals with -1. The variable default is set in variables.yaml (separate commit). Signed-off-by: Jaehyun Kim <jhkim@precisioninno.com>
Print an informational message when the sort workaround is active so users can confirm it is being applied. Signed-off-by: Jaehyun Kim <jhkim@precisioninno.com>
Add the variable definition with default: 1 (on-by-default) following the standard ORFS 0/1 boolean convention. Signed-off-by: Jaehyun Kim <jhkim@precisioninno.com>
Regenerate FlowVariables.md from variables.yaml to include the new SYNTH_SORT_BEFORE_ABC variable. Signed-off-by: Jaehyun Kim <jhkim@precisioninno.com>
…ate/OpenROAD-flow-scripts into secure-workaround-yosys-nd Signed-off-by: Jaehyun Kim <jhkim@precisioninno.com>
Update metrics from CI run after master merge. Fix nangate45/swerv_wrapper GRT congestion by reducing PLACE_DENSITY_LB_ADDON from 0.08 to 0.05. designs/asap7/aes-block/rules-base.json updates: | Metric | Old | New | Type | | ------ | --- | --- | ---- | | cts__timing__setup__tns | -2890.0 | -3330.0 | Failing | | cts__timing__hold__tns | -5670.0 | -4970.0 | Tighten | | globalroute__timing__setup__tns | -3020.0 | -2880.0 | Tighten | | globalroute__timing__hold__ws | -25.9 | -49.0 | Failing | | globalroute__timing__hold__tns | -1080.0 | -1360.0 | Failing | | finish__timing__setup__ws | -58.1 | -56.7 | Tighten | | finish__timing__setup__tns | -897.0 | -614.0 | Tighten | | finish__timing__hold__tns | -90.0 | -201.0 | Failing | See metric_update_table.md for full metric update details. Signed-off-by: Jaehyun Kim <jhkim@precisioninno.com>
designs/rapidus2hp/hercules_idecode/rules-verific.json updates: | Metric | Old | New | Type | | ------ | --- | --- | ---- | | placeopt__design__instance__count__stdcell | 232846 | 232170 | Tighten | | cts__design__instance__count__setup_buffer | 20248 | 20189 | Tighten | | cts__design__instance__count__hold_buffer | 20248 | 20189 | Tighten | | globalroute__antenna_diodes_count | 202 | 201 | Tighten | | globalroute__timing__setup__tns | -0.0993 | -0.295 | Failing | | finish__timing__setup__tns | -0.0993 | -0.296 | Failing | designs/rapidus2hp/gcd/rules-verific.json updates: | Metric | Old | New | Type | | ------ | --- | --- | ---- | | placeopt__design__instance__count__stdcell | 688 | 677 | Tighten | | cts__timing__setup__ws | -0.0221 | -0.0275 | Failing | | cts__timing__setup__tns | -0.475 | -0.19 | Tighten | | globalroute__timing__setup__ws | -0.0302 | -0.0378 | Failing | | globalroute__timing__setup__tns | -0.753 | -0.616 | Tighten | | finish__timing__setup__ws | -0.0302 | -0.0378 | Failing | | finish__timing__setup__tns | -0.753 | -0.616 | Tighten | designs/rapidus2hp/hercules_is_int/rules-verific.json updates: | Metric | Old | New | Type | | ------ | --- | --- | ---- | | placeopt__design__instance__count__stdcell | 646997 | 642088 | Tighten | | cts__design__instance__count__setup_buffer | 56261 | 55834 | Tighten | | cts__design__instance__count__hold_buffer | 56261 | 55834 | Tighten | | globalroute__antenna_diodes_count | 567 | 562 | Tighten | | globalroute__timing__setup__tns | -107.0 | -145.0 | Failing | | finish__timing__setup__tns | -107.0 | -145.0 | Failing | designs/rapidus2hp/ibex/rules-verific.json updates: | Metric | Old | New | Type | | ------ | --- | --- | ---- | | globalroute__timing__setup__tns | -0.152 | -2.78 | Failing | | finish__timing__setup__tns | -0.152 | -2.86 | Failing | Signed-off-by: Jaehyun Kim <jhkim@precisioninno.com>
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Summary
sortcommand before abc execution insynth.tclto stabilize module iteration orderabc_newvisits modules indictinsertion order which can vary between runs, producing different netlists from the same RTL inputnangate45/swerv_wrapper)SYNTH_SORT_BEFORE_ABC=-1Closes #4056