cpu: Add a memory access predicate

This changeset introduces a new predicate to guard memory accesses.
The most immediate use for this is to allow proper handling of
predicated-false vector contiguous loads and predicated-false
micro-ops of vector gather loads (added in separate changesets).

Change-Id: Ice6894fe150faec2f2f7ab796a00c99ac843810a
Signed-off-by: Giacomo Gabrielli <giacomo.gabrielli@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17991
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Bradley Wang <radwang@ucdavis.edu>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/src/cpu/o3/lsq_unit_impl.hh b/src/cpu/o3/lsq_unit_impl.hh
index 62402bf4f..9323e8634 100644
--- a/src/cpu/o3/lsq_unit_impl.hh
+++ b/src/cpu/o3/lsq_unit_impl.hh
@@ -542,6 +542,16 @@ LSQUnit<Impl>::executeLoad(const DynInstPtr &inst)
 
     load_fault = inst->initiateAcc();
 
+    if (!inst->readMemAccPredicate()) {
+        assert(load_fault == NoFault);
+        assert(inst->readPredicate());
+        inst->setExecuted();
+        inst->completeAcc(nullptr);
+        iewStage->instToCommit(inst);
+        iewStage->activityThisCycle();
+        return NoFault;
+    }
+
     if (inst->isTranslationDelayed() && load_fault == NoFault)
         return load_fault;