Forward exceptions from segment micro-ops - #490
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Pull request overview
This PR fixes a hang scenario in the segment memory micro-op sequencer where backend exceptions could be dropped while response forwarding is suppressed during sequencing, potentially leaving the dispatcher waiting indefinitely.
Changes:
- Capture and forward exception responses from
SEGMENT_MICRO_OPSby latchingara_resp_iand terminating sequencing early. - Continue monitoring backend responses while draining outstanding micro-ops in
SEGMENT_MICRO_OPS_WAIT_ENDso late exceptions are not lost.
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A backend exception from a segment micro-op was discarded because response forwarding is suppressed while sequencing, while the exception arm was empty. This could leave the dispatcher waiting indefinitely after the backend stopped accepting work.
Capture the exception response and end segment sequencing immediately. Also monitor responses while draining previously issued micro-ops so an exception from the last outstanding operation is not lost.
Verification: a standalone Verilator testbench covers nf=2/3/8, exceptions on the first/middle/last micro-op, a backend that stops responding after the fault, plus a backend that deasserts ready. All 11 scenarios complete with the expected response.