Fixed bug in LICM

Rationale:
We should stop hoisting anything that can throw
as soon as something else that can do something
visible (either throw or write something) is *not*
hoisted (used to be just throw test on second part).

Bug: 32810295
Test: test-art-host
Change-Id: Id88b712a5d9e37598d0bebbd4ecf4b1d8ee787b5

1 files changed, 10 insertions, 10 deletions

diff --git a/compiler/optimizing/licm.cc b/compiler/optimizing/licm.cc
index eb2d18dd88..f0086fb202 100644
--- a/compiler/optimizing/licm.cc
+++ b/compiler/optimizing/licm.cc
@@ -120,17 +120,17 @@ void LICM::Run() {
       }
       DCHECK(!loop_info->IsIrreducible());
 
-      // We can move an instruction that can throw only if it is the first
-      // throwing instruction in the loop. Note that the first potentially
-      // throwing instruction encountered that is not hoisted stops this
-      // optimization. Non-throwing instruction can still be hoisted.
-      bool found_first_non_hoisted_throwing_instruction_in_loop = !inner->IsLoopHeader();
+      // We can move an instruction that can throw only as long as it is the first visible
+      // instruction (throw or write) in the loop. Note that the first potentially visible
+      // instruction that is not hoisted stops this optimization. Non-throwing instructions,
+      // on the other hand, can still be hoisted.
+      bool found_first_non_hoisted_visible_instruction_in_loop = !inner->IsLoopHeader();
       for (HInstructionIterator inst_it(inner->GetInstructions());
            !inst_it.Done();
            inst_it.Advance()) {
         HInstruction* instruction = inst_it.Current();
         if (instruction->CanBeMoved()
-            && (!instruction->CanThrow() || !found_first_non_hoisted_throwing_instruction_in_loop)
+            && (!instruction->CanThrow() || !found_first_non_hoisted_visible_instruction_in_loop)
             && !instruction->GetSideEffects().MayDependOn(loop_effects)
             && InputsAreDefinedBeforeLoop(instruction)) {
           // We need to update the environment if the instruction has a loop header
@@ -142,10 +142,10 @@ void LICM::Run() {
           }
           instruction->MoveBefore(pre_header->GetLastInstruction());
           MaybeRecordStat(MethodCompilationStat::kLoopInvariantMoved);
-        } else if (instruction->CanThrow()) {
-          // If `instruction` can throw, we cannot move further instructions
-          // that can throw as well.
-          found_first_non_hoisted_throwing_instruction_in_loop = true;
+        } else if (instruction->CanThrow() || instruction->DoesAnyWrite()) {
+          // If `instruction` can do something visible (throw or write),
+          // we cannot move further instructions that can throw.
+          found_first_non_hoisted_visible_instruction_in_loop = true;
         }
       }
     }