Don't try to hoist an instruction out of a loop it belongs in

We can improve our code sinking heuristics to not try to hoist
an instruction out of a loop it was already in. In some cases,
we were successful in removing the instruction from the loop,
breaking the domination.

Bug: 269927803
Fixes: 269927803
Test: art/test/testrunner/testrunner.py --host --64 --optimizing -b
Test: dex2oat compiling the app in the bug
Change-Id: Id563a2e87798d74833081e254b2856937bdf7e2c

1 files changed, 4 insertions, 3 deletions

diff --git a/compiler/optimizing/code_sinking.cc b/compiler/optimizing/code_sinking.cc
index 42679337b7..e7a4389ed2 100644
--- a/compiler/optimizing/code_sinking.cc
+++ b/compiler/optimizing/code_sinking.cc
@@ -171,7 +171,6 @@ static bool ShouldFilterUse(HInstruction* instruction,
   return false;
 }
 
-
 // Find the ideal position for moving `instruction`. If `filter` is true,
 // we filter out store instructions to that instruction, which are processed
 // first in the step (3) of the sinking algorithm.
@@ -210,8 +209,10 @@ static HInstruction* FindIdealPosition(HInstruction* instruction,
     return nullptr;
   }
 
-  // Move to the first dominator not in a loop, if we can.
-  while (target_block->IsInLoop()) {
+  // Move to the first dominator not in a loop, if we can. We only do this if we are trying to hoist
+  // `instruction` out of a loop it wasn't a part of.
+  const HLoopInformation* loop_info = instruction->GetBlock()->GetLoopInformation();
+  while (target_block->IsInLoop() && target_block->GetLoopInformation() != loop_info) {
     if (!post_dominated.IsBitSet(target_block->GetDominator()->GetBlockId())) {
       break;
     }