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cpu: fix how branching is handled when a thread is suspended in MinorCPU

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When a thread is suspended, all instructions after the suspension need
to be discarded since the thread will take a different execution stream
when it wakes up.

To do that, in MinorCPU, whenever a thread gets suspended, we change the
current execution stream by updating the current branch with
BranchData::SuspendThread reason.

Change-Id: I7cdcda22c1cf6e8ac8db8800b7d9ec052433fdf3
Reviewed-on: https://gem5-review.googlesource.com/c/9626
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Giacomo Gabrielli <giacomo.gabrielli@gmail.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
This commit is contained in:
Tuan Ta
2018-04-02 16:22:16 -04:00
parent 6a6668bbc4
commit e437086341
1 changed files with 9 additions and 3 deletions
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12
src/cpu/minor/execute.cc
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@@ -248,7 +248,14 @@ Execute::tryToBranch(MinorDynInstPtr inst, Fault fault, BranchData &branch)
pc_before, target);
}
if (inst->predictedTaken && !force_branch) {
if (thread->status() == ThreadContext::Suspended) {
/* Thread got suspended */
DPRINTF(Branch, "Thread got suspended: branch from 0x%x to 0x%x "
"inst: %s\n",
inst->pc.instAddr(), target.instAddr(), *inst);
reason = BranchData::SuspendThread;
} else if (inst->predictedTaken && !force_branch) {
/* Predicted to branch */
if (!must_branch) {
/* No branch was taken, change stream to get us back to the
@@ -1054,8 +1061,7 @@ Execute::commit(ThreadID thread_id, bool only_commit_microops, bool discard,
!branch.isStreamChange() && /* No real branch */
fault == NoFault && /* No faults */
completed_inst && /* Still finding instructions to execute */
num_insts_committed != commitLimit && /* Not reached commit limit */
cpu.getContext(thread_id)->status() != ThreadContext::Suspended
num_insts_committed != commitLimit /* Not reached commit limit */
)
{
if (only_commit_microops) {