cpu: Fix o3 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 at rename.

1 files changed, 0 insertions, 3 deletions

diff --git a/src/cpu/o3/fetch.hh b/src/cpu/o3/fetch.hh
index eba4469c0..0c1b81d86 100644
--- a/src/cpu/o3/fetch.hh
+++ b/src/cpu/o3/fetch.hh
@@ -434,9 +434,6 @@ class DefaultFetch
     /** Source of possible stalls. */
     struct Stalls {
         bool decode;
-        bool rename;
-        bool iew;
-        bool commit;
         bool drain;
     };