rsz: detect cross-clock-domain hold violations on clock-as-data endpoints (#8075)#10718
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rsz: detect cross-clock-domain hold violations on clock-as-data endpoints (#8075)#10718saurav-fermions wants to merge 1 commit into
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…ints (The-OpenROAD-Project#8075) findHoldViolations excluded every endpoint for which Sta::isClock() is true. isClock() reports any pin in a clock network's combinational fanout, which also includes register data (D) pins that sample a signal sourced from a clock -- e.g. a clock used as data that crosses into a different sampling-clock domain. Those D pins are legitimate hold endpoints, so repair_timing -hold silently reported "No hold violations found" while a real hold violation remained (issue The-OpenROAD-Project#8075). Refine the exclusion to skip only true clock-tree pins: pins that are on the clock network AND carry no timing check (!Vertex::hasChecks()). Register data pins that hold a setup/hold check are kept, so cross-clock -domain hold violations are detected and repaired. Clock-tree pins are still excluded as before. Add regression test repair_hold_clock_as_data where clk1 is used both as a clock (for r1) and as data into r2/D (r2 clocked by clk2). On the unfixed code RSZ reports "No hold violations found" and r2/D stays at -0.59; with the fix the endpoint is detected and repaired to >= 0. Registered in both CMake and Bazel. Signed-off-by: Saurav Singh <saurav.singh@fermions.co>
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This pull request addresses OpenROAD issue #8075 by updating RepairHold::findHoldViolations to ensure that register data pins sampling a signal sourced from a clock (cross-clock-domain endpoints) are not incorrectly skipped during hold repair. This is achieved by only excluding clock tree endpoints that do not have timing checks. Additionally, a new integration test (repair_hold_clock_as_data) has been added to verify this behavior. I have no feedback to provide as there are no review comments.
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Summary
RepairHold::findHoldViolationsskipped endpoints whose pin is a clock pin, so a hold violation on a clock-as-data endpoint was never repaired. This detects cross-clock-domain hold violations on clock-as-data endpoints.Type of Change
Impact
Hold violations on clock-as-data endpoints are now detected and repaired.
Verification
ctest -R '^rsz\.'239/239; real fail/pass viarepair_hold_clock_as_data.Related Issues
Fixes #8075
Developed with SAIGE, Fermions' autonomous RTL/EDA debugging agent; root-caused, tested, and signed off by the submitter (@saurav-fermions).