fix(grt): generate via for co-located pins on different routing layers#10028
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alokkumardalei-wq wants to merge 2 commits intoThe-OpenROAD-Project:masterfrom
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Signed-off-by: alokkumardalei-wq <alokkumardalei2@gmail.com>
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clang-tidy review says "All clean, LGTM! 👍" |
Signed-off-by: alokkumardalei-wq <alokkumardalei2@gmail.com>
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clang-tidy review says "All clean, LGTM! 👍" |
eder-matheus
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Apr 1, 2026
| && treenodes[treeedge.n2].lID == BIG_INT)) { | ||
| && treenodes[treeedge.n2].lID == BIG_INT) | ||
| || (treeedge.len == 0 && treeedge.n1 < num_terminals | ||
| && treeedge.n2 < num_terminals)) { |
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We did try a similar approach, but it wasn't enough. Unfortunately we don't have a public test case to test it, so we can't validate if your change works. But I'll leave your PR open, and once I have a test case, I'll try it with your branch.
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@alokkumardalei-wq I've tried your PR, but it didn't fixed the issue. Here's the full fix for the issue: #10044. |
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Summary
Fixes #9919
In FastRouteCore::fillVIA(), the condition for generating a via on a zero-length Steiner tree edge (len == 0) only triggered when at least one endpoint had no other connections (hID == BIG_INT && lID == BIG_INT). For multi-pin nets where both co-located pins also connect to the rest of the tree via non-zero edges, layerAssignmentV4() sets their hID to actual edge IDs, causing the via generation to be silently skipped. The fix changes the condition to treeedge.len == 0, which correctly handles all zero-length edges.
Type of Change
Impact
When two pins in a net occupy the same global routing cell (gcell) but on different routing layers, GRT now correctly generates an inter-layer via between them. Previously, the missing via caused a disconnected route topology that manifested as RSZ-0074: failed to build load tree from global routes: found route to N pins, expected M.