[gem5-dev] changeset in gem5: cpu: Fix o3 quiesce fetch bug

[Mitch Hayenga via gem5-dev]

changeset 1ba825974ee6 in /z/repo/gem5
details: http://repo.gem5.org/gem5?cmd=changeset;node=1ba825974ee6
description:
        cpu: Fix o3 quiesce fetch bug

        O3 is supposed to stop fetching instructions once a quiesce is 
encountered.
        However due to a bug, it would continue fetching instructions from the 
current
        fetch buffer.  This is because of a break statment that only broke out 
of the
        first of 2 nested loops.  It should have broken out of both.

diffstat:

 src/cpu/o3/fetch_impl.hh |  8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diffs (34 lines):

diff -r ed05298e8566 -r 1ba825974ee6 src/cpu/o3/fetch_impl.hh
--- a/src/cpu/o3/fetch_impl.hh  Wed Sep 03 07:42:37 2014 -0400
+++ b/src/cpu/o3/fetch_impl.hh  Wed Sep 03 07:42:38 2014 -0400
@@ -1236,6 +1236,9 @@
     // ended this fetch block.
     bool predictedBranch = false;
 
+    // Need to halt fetch if quiesce instruction detected
+    bool quiesce = false;
+
     TheISA::MachInst *cacheInsts =
         reinterpret_cast<TheISA::MachInst *>(fetchBuffer[tid]);
 
@@ -1246,7 +1249,7 @@
     // Keep issuing while fetchWidth is available and branch is not
     // predicted taken
     while (numInst < fetchWidth && fetchQueue[tid].size() < fetchQueueSize
-           && !predictedBranch) {
+           && !predictedBranch && !quiesce) {
         // We need to process more memory if we aren't going to get a
         // StaticInst from the rom, the current macroop, or what's already
         // in the decoder.
@@ -1363,9 +1366,10 @@
 
             if (instruction->isQuiesce()) {
                 DPRINTF(Fetch,
-                        "Quiesce instruction encountered, halting fetch!");
+                        "Quiesce instruction encountered, halting fetch!\n");
                 fetchStatus[tid] = QuiescePending;
                 status_change = true;
+                quiesce = true;
                 break;
             }
         } while ((curMacroop || decoder[tid]->instReady()) &&
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