Gabe Black has uploaded this change for review. (
https://gem5-review.googlesource.com/7124
Change subject: cpu: Use the NotAnInst flag to avoid passing an inst to
fetch faults.
......................................................................
cpu: Use the NotAnInst flag to avoid passing an inst to fetch faults.
When a fault happens in fetch in O3, a dummy inst is created to carry
the fault through the pipeline to commit, but conceptually there isn't
actually any instruction since we failed to fetch one.
This change marks the dummy instruction as NotAnInst, and when any
such instruction gets to commit, the fault object associated with it
is invoked and passed a null static inst pointer instead of a pointer
to the dummy inst.
Change-Id: I18d993083406deb625402e06af4ba0d4772ca5a3
---
M src/cpu/o3/commit_impl.hh
M src/cpu/o3/fetch_impl.hh
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/src/cpu/o3/commit_impl.hh b/src/cpu/o3/commit_impl.hh
index b3a97ad..d32493c 100644
--- a/src/cpu/o3/commit_impl.hh
+++ b/src/cpu/o3/commit_impl.hh
@@ -1225,7 +1225,10 @@
// needed to update the state as soon as possible. This
// prevents external agents from changing any specific state
// that the trap need.
- cpu->trap(inst_fault, tid, head_inst->staticInst);
+ cpu->trap(inst_fault, tid,
+ head_inst->notAnInst() ?
+ StaticInst::nullStaticInstPtr :
+ head_inst->staticInst);
// Exit state update mode to avoid accidental updating.
thread[tid]->noSquashFromTC = false;
diff --git a/src/cpu/o3/fetch_impl.hh b/src/cpu/o3/fetch_impl.hh
index 6cca77a..d879342 100644
--- a/src/cpu/o3/fetch_impl.hh
+++ b/src/cpu/o3/fetch_impl.hh
@@ -729,6 +729,7 @@
// We will use a nop in ordier to carry the fault.
DynInstPtr instruction = buildInst(tid,
StaticInst::nopStaticInstPtr,
NULL, fetchPC, fetchPC, false);
+ instruction->setNotAnInst();
instruction->setPredTarg(fetchPC);
instruction->fault = fault;
--
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Gerrit-Project: public/gem5
Gerrit-Branch: master
Gerrit-MessageType: newchange
Gerrit-Change-Id: I18d993083406deb625402e06af4ba0d4772ca5a3
Gerrit-Change-Number: 7124
Gerrit-PatchSet: 1
Gerrit-Owner: Gabe Black <[email protected]>
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