optimizing: NullCheck elimination
How it works:
- run a type analysis to propagate null information on instructions
- during the last instruction simplifier remove null checks for which
the input is known to be not null
The current type analysis is actually a nullability analysis but it will
be reused in follow up CLs to propagate type information: so it keeps
the more convenient name.
Change-Id: I54bb1d32ab24604b4d677d1ecdaf8d60a5ff5ce9
diff --git a/compiler/optimizing/instruction_simplifier.cc b/compiler/optimizing/instruction_simplifier.cc
index 63bc4ae..17c8f33 100644
--- a/compiler/optimizing/instruction_simplifier.cc
+++ b/compiler/optimizing/instruction_simplifier.cc
@@ -27,6 +27,7 @@
void VisitEqual(HEqual* equal) OVERRIDE;
void VisitArraySet(HArraySet* equal) OVERRIDE;
void VisitTypeConversion(HTypeConversion* instruction) OVERRIDE;
+ void VisitNullCheck(HNullCheck* instruction) OVERRIDE;
};
void InstructionSimplifier::Run() {
@@ -34,6 +35,14 @@
visitor.VisitInsertionOrder();
}
+void InstructionSimplifierVisitor::VisitNullCheck(HNullCheck* null_check) {
+ HInstruction* obj = null_check->InputAt(0);
+ if (!obj->CanBeNull()) {
+ null_check->ReplaceWith(obj);
+ null_check->GetBlock()->RemoveInstruction(null_check);
+ }
+}
+
void InstructionSimplifierVisitor::VisitSuspendCheck(HSuspendCheck* check) {
HBasicBlock* block = check->GetBlock();
// Currently always keep the suspend check at entry.