[vm/compiler] Avoid redundant spilling of SIMD values.

mraleph · commit-bot@chromium.org · commit 2497606fed87 · 2020-05-11T20:24:57.000Z
There was a code in the register allocator that recognized whether destination is a spill slot or not by checking if it is one of different location types. By accident QuadSpillSlot was missing from that list - and as a result we were emitting redundant moves when connecting split siblings after register allocation. Change the code to just ask parent live which spill slot it was assigned and use that to drive decisions. dart-lang/sdk#41805 Change-Id: I73e208acd0bf86dceeaad970b8e5cbcb9c3f8eaa Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/147550 Reviewed-by: Daco Harkes <dacoharkes@google.com> Reviewed-by: Martin Kustermann <kustermann@google.com> Commit-Queue: Vyacheslav Egorov <vegorov@google.com>
diff --git a/runtime/vm/compiler/backend/linearscan.cc b/runtime/vm/compiler/backend/linearscan.cc
@@ -2722,12 +2722,7 @@ void FlowGraphAllocator::AllocateUnallocatedRanges() {
 
 bool FlowGraphAllocator::TargetLocationIsSpillSlot(LiveRange* range,
                                                    Location target) {
-  if (target.IsStackSlot() || target.IsDoubleStackSlot() ||
-      target.IsConstant()) {
-    ASSERT(GetLiveRange(range->vreg())->spill_slot().Equals(target));
-    return true;
-  }
-  return false;
+  return GetLiveRange(range->vreg())->spill_slot().Equals(target);
 }
 
 void FlowGraphAllocator::ConnectSplitSiblings(LiveRange* parent,
@@ -2843,11 +2838,7 @@ void FlowGraphAllocator::ResolveControlFlow() {
   // this will cause spilling to occur on the fast path (at the definition).
   for (intptr_t i = 0; i < spilled_.length(); i++) {
     LiveRange* range = spilled_[i];
-    if (range->assigned_location().IsStackSlot() ||
-        range->assigned_location().IsDoubleStackSlot() ||
-        range->assigned_location().IsConstant()) {
-      ASSERT(range->assigned_location().Equals(range->spill_slot()));
-    } else {
+    if (!range->assigned_location().Equals(range->spill_slot())) {
       AddMoveAt(range->Start() + 1, range->spill_slot(),
                 range->assigned_location());
     }
