synth: strip src attributes again after techmap under SYNTH_REPEATABLE_BUILD - #4543
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maliberty merged 1 commit intoSep 19, 2026
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…E_BUILD SYNTH_REPEATABLE_BUILD strips src attributes in synth_canonicalize.tcl so source paths and line numbers cannot perturb the canonical RTLIL hash. The techmap passes that follow in synth.tcl re-attach src attributes, now pointing into the techmap library files (ADDER_MAP_FILE, LATCH_MAP_FILE, DFF_MAP_FILE and yosys' own techmap.v). Under Bazel those live below the output base, so 1_2_yosys.v carries absolute build paths: the same design synthesised in two output bases produced netlists that differed only in those strings, defeating the knob's purpose. Strip src again, under the same guard, right before 1_2_yosys.v is written. Verified on a hierarchical design synthesised in two Bazel output bases: the netlists become byte-identical where they previously differed only in src paths. Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>
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This pull request introduces a check for the SYNTH_REPEATABLE_BUILD environment variable in flow/scripts/synth.tcl to strip src attributes and ensure repeatable builds. The review feedback correctly identifies that directly accessing the environment variable will cause a Tcl error if it is not defined, and suggests using the env_var_equals helper function to safely check its value.
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🔍 QoR checkMetrics reflect the PR merge build — i.e. what will land on the target branch. Commit 62 design(s) checked — 0 with regression(s), 1 without a comparable baseline. |
maliberty
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Sep 19, 2026
maliberty
merged commit Sep 19, 2026
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SYNTH_REPEATABLE_BUILD (#3797) strips
srcattributes insynth_canonicalize.tcl, but thetechmappasses insynth.tclre-attach them pointing into the techmap library, so1_2_yosys.vstill carries absolute build paths.Strip them again before
1_2_yosys.vis written, under the same guard. Netlists from two Bazel output bases are now byte-identical.