Review Board 2.0.15


o3: Fix front-end pipeline interlock behavior

Review Request #2296 - Created June 12, 2014 and submitted

Information
Ali Saidi
gem5
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Reviewers
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Changeset 10251:faaade247267
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o3: Fix front-end pipeline interlock behavior

The o3 pipeline interlock/stall logic is incorrect.  o3 unnecessicarily stalled
fetch and decode due to later stages in the pipeline.  In general, a stage
should usually only consider if it is stalled by the adjacent, downstream stage.
Forcing stalls due to later stages creates and results in bubbles in the
pipeline.  Additionally, o3 stalled the entire frontend (fetch, decode, rename)
on a branch mispredict while the ROB is being serially walked to update the
RAT (robSquashing). Only should have stalled @ rename.

   
Review request changed
Updated (Sept. 3, 2014, 4:40 a.m.)

Status: Closed (submitted)