Adjust safepoint position of implicit null checks.

The safepoint records stack masks and register masks. For implicit
null checks, they need to have their position to the instruction
doing the null check (the next one).

Test: org.apache.harmony.tests.java.io.BufferedWriterTest#test_write_LStringII_Exception
Change-Id: I347d9fe38fb9df23fbc00f9aa36f1ee9c54bf912

1 files changed, 15 insertions, 2 deletions

diff --git a/compiler/optimizing/ssa_liveness_analysis.h b/compiler/optimizing/ssa_liveness_analysis.h
index cebd4adcd8..dfe6103e04 100644
--- a/compiler/optimizing/ssa_liveness_analysis.h
+++ b/compiler/optimizing/ssa_liveness_analysis.h
@@ -230,12 +230,25 @@ class SafepointPosition : public ArenaObject<kArenaAllocSsaLiveness> {
       : instruction_(instruction),
         next_(nullptr) {}
 
+  static size_t ComputePosition(HInstruction* instruction) {
+    // We special case instructions emitted at use site, as their
+    // safepoint position needs to be at their use.
+    if (instruction->IsEmittedAtUseSite()) {
+      // Currently only applies to implicit null checks, which are emitted
+      // at the next instruction.
+      DCHECK(instruction->IsNullCheck()) << instruction->DebugName();
+      return instruction->GetLifetimePosition() + 2;
+    } else {
+      return instruction->GetLifetimePosition();
+    }
+  }
+
   void SetNext(SafepointPosition* next) {
     next_ = next;
   }
 
   size_t GetPosition() const {
-    return instruction_->GetLifetimePosition();
+    return ComputePosition(instruction_);
   }
 
   SafepointPosition* GetNext() const {
@@ -922,7 +935,7 @@ class LiveInterval : public ArenaObject<kArenaAllocSsaLiveness> {
     if (first_safepoint_ == nullptr) {
       first_safepoint_ = last_safepoint_ = safepoint;
     } else {
-      DCHECK_LT(last_safepoint_->GetPosition(), safepoint->GetPosition());
+      DCHECK_LE(last_safepoint_->GetPosition(), safepoint->GetPosition());
       last_safepoint_->SetNext(safepoint);
       last_safepoint_ = safepoint;
     }