ART: Naive NullCheck elimination in InstructionBuilder
Save a little bit of memory by not generating trivially redundant
HNullCheck instructions. This patch builds on the fact that the
InstructionBuilder now directly generates SSA form and looks at the
input of the NullCheck. For obvious cases, such as NewInstance/Array
or `this`, the NullCheck generation is completely avoided.
Bug: 28173563
Change-Id: I1fdf3b096c7a939f7b8586c02a2a6b44dfa43443
(cherry picked from commit c120bbe26fe116d3c9d8322f44bb9e330e07f745)
diff --git a/compiler/optimizing/instruction_builder.cc b/compiler/optimizing/instruction_builder.cc
index f5e49c2..6733b3a 100644
--- a/compiler/optimizing/instruction_builder.cc
+++ b/compiler/optimizing/instruction_builder.cc
@@ -215,6 +215,17 @@
}
}
+HInstruction* HInstructionBuilder::LoadNullCheckedLocal(uint32_t register_index, uint32_t dex_pc) {
+ HInstruction* ref = LoadLocal(register_index, Primitive::kPrimNot);
+ if (!ref->CanBeNull()) {
+ return ref;
+ }
+
+ HNullCheck* null_check = new (arena_) HNullCheck(ref, dex_pc);
+ AppendInstruction(null_check);
+ return null_check;
+}
+
void HInstructionBuilder::SetLoopHeaderPhiInputs() {
for (size_t i = loop_headers_.size(); i > 0; --i) {
HBasicBlock* block = loop_headers_[i - 1];
@@ -1084,10 +1095,9 @@
size_t start_index = 0;
size_t argument_index = 0;
if (invoke->GetOriginalInvokeType() != InvokeType::kStatic) { // Instance call.
- HInstruction* arg = LoadLocal(is_range ? register_index : args[0], Primitive::kPrimNot);
- HNullCheck* null_check = new (arena_) HNullCheck(arg, invoke->GetDexPc());
- AppendInstruction(null_check);
- invoke->SetArgumentAt(0, null_check);
+ HInstruction* arg = LoadNullCheckedLocal(is_range ? register_index : args[0],
+ invoke->GetDexPc());
+ invoke->SetArgumentAt(0, arg);
start_index = 1;
argument_index = 1;
}
@@ -1193,9 +1203,7 @@
compiler_driver_->ComputeInstanceFieldInfo(field_index, dex_compilation_unit_, is_put, soa);
- HInstruction* object = LoadLocal(obj_reg, Primitive::kPrimNot);
- HInstruction* null_check = new (arena_) HNullCheck(object, dex_pc);
- AppendInstruction(null_check);
+ HInstruction* object = LoadNullCheckedLocal(obj_reg, dex_pc);
Primitive::Type field_type = (resolved_field == nullptr)
? GetFieldAccessType(*dex_file_, field_index)
@@ -1205,14 +1213,14 @@
HInstruction* field_set = nullptr;
if (resolved_field == nullptr) {
MaybeRecordStat(MethodCompilationStat::kUnresolvedField);
- field_set = new (arena_) HUnresolvedInstanceFieldSet(null_check,
+ field_set = new (arena_) HUnresolvedInstanceFieldSet(object,
value,
field_type,
field_index,
dex_pc);
} else {
uint16_t class_def_index = resolved_field->GetDeclaringClass()->GetDexClassDefIndex();
- field_set = new (arena_) HInstanceFieldSet(null_check,
+ field_set = new (arena_) HInstanceFieldSet(object,
value,
field_type,
resolved_field->GetOffset(),
@@ -1228,13 +1236,13 @@
HInstruction* field_get = nullptr;
if (resolved_field == nullptr) {
MaybeRecordStat(MethodCompilationStat::kUnresolvedField);
- field_get = new (arena_) HUnresolvedInstanceFieldGet(null_check,
+ field_get = new (arena_) HUnresolvedInstanceFieldGet(object,
field_type,
field_index,
dex_pc);
} else {
uint16_t class_def_index = resolved_field->GetDeclaringClass()->GetDexClassDefIndex();
- field_get = new (arena_) HInstanceFieldGet(null_check,
+ field_get = new (arena_) HInstanceFieldGet(object,
field_type,
resolved_field->GetOffset(),
resolved_field->IsVolatile(),
@@ -1449,10 +1457,7 @@
uint8_t array_reg = instruction.VRegB_23x();
uint8_t index_reg = instruction.VRegC_23x();
- HInstruction* object = LoadLocal(array_reg, Primitive::kPrimNot);
- object = new (arena_) HNullCheck(object, dex_pc);
- AppendInstruction(object);
-
+ HInstruction* object = LoadNullCheckedLocal(array_reg, dex_pc);
HInstruction* length = new (arena_) HArrayLength(object, dex_pc);
AppendInstruction(length);
HInstruction* index = LoadLocal(index_reg, Primitive::kPrimInt);
@@ -1527,11 +1532,8 @@
}
void HInstructionBuilder::BuildFillArrayData(const Instruction& instruction, uint32_t dex_pc) {
- HInstruction* array = LoadLocal(instruction.VRegA_31t(), Primitive::kPrimNot);
- HNullCheck* null_check = new (arena_) HNullCheck(array, dex_pc);
- AppendInstruction(null_check);
-
- HInstruction* length = new (arena_) HArrayLength(null_check, dex_pc);
+ HInstruction* array = LoadNullCheckedLocal(instruction.VRegA_31t(), dex_pc);
+ HInstruction* length = new (arena_) HArrayLength(array, dex_pc);
AppendInstruction(length);
int32_t payload_offset = instruction.VRegB_31t() + dex_pc;
@@ -1547,28 +1549,28 @@
switch (payload->element_width) {
case 1:
- BuildFillArrayData(null_check,
+ BuildFillArrayData(array,
reinterpret_cast<const int8_t*>(data),
element_count,
Primitive::kPrimByte,
dex_pc);
break;
case 2:
- BuildFillArrayData(null_check,
+ BuildFillArrayData(array,
reinterpret_cast<const int16_t*>(data),
element_count,
Primitive::kPrimShort,
dex_pc);
break;
case 4:
- BuildFillArrayData(null_check,
+ BuildFillArrayData(array,
reinterpret_cast<const int32_t*>(data),
element_count,
Primitive::kPrimInt,
dex_pc);
break;
case 8:
- BuildFillWideArrayData(null_check,
+ BuildFillWideArrayData(array,
reinterpret_cast<const int64_t*>(data),
element_count,
dex_pc);
@@ -2575,9 +2577,7 @@
ARRAY_XX(_SHORT, Primitive::kPrimShort);
case Instruction::ARRAY_LENGTH: {
- HInstruction* object = LoadLocal(instruction.VRegB_12x(), Primitive::kPrimNot);
- object = new (arena_) HNullCheck(object, dex_pc);
- AppendInstruction(object);
+ HInstruction* object = LoadNullCheckedLocal(instruction.VRegB_12x(), dex_pc);
AppendInstruction(new (arena_) HArrayLength(object, dex_pc));
UpdateLocal(instruction.VRegA_12x(), current_block_->GetLastInstruction());
break;
diff --git a/compiler/optimizing/instruction_builder.h b/compiler/optimizing/instruction_builder.h
index 070f7da..0e3e5a7 100644
--- a/compiler/optimizing/instruction_builder.h
+++ b/compiler/optimizing/instruction_builder.h
@@ -87,6 +87,7 @@
ArenaVector<HInstruction*>* GetLocalsFor(HBasicBlock* block);
HInstruction* ValueOfLocalAt(HBasicBlock* block, size_t local);
HInstruction* LoadLocal(uint32_t register_index, Primitive::Type type) const;
+ HInstruction* LoadNullCheckedLocal(uint32_t register_index, uint32_t dex_pc);
void UpdateLocal(uint32_t register_index, HInstruction* instruction);
void AppendInstruction(HInstruction* instruction);
diff --git a/test/444-checker-nce/src/Main.java b/test/444-checker-nce/src/Main.java
index c96b18c..ddc2f77 100644
--- a/test/444-checker-nce/src/Main.java
+++ b/test/444-checker-nce/src/Main.java
@@ -28,10 +28,6 @@
}
/// CHECK-START: Main Main.thisTest() builder (after)
- /// CHECK: NullCheck
- /// CHECK: InvokeStaticOrDirect
-
- /// CHECK-START: Main Main.thisTest() instruction_simplifier (after)
/// CHECK-NOT: NullCheck
/// CHECK: InvokeStaticOrDirect
public Main thisTest() {
@@ -40,12 +36,10 @@
/// CHECK-START: Main Main.newInstanceRemoveTest() builder (after)
/// CHECK: NewInstance
- /// CHECK: NullCheck
/// CHECK: InvokeStaticOrDirect
- /// CHECK: NullCheck
/// CHECK: InvokeStaticOrDirect
- /// CHECK-START: Main Main.newInstanceRemoveTest() instruction_simplifier (after)
+ /// CHECK-START: Main Main.newInstanceRemoveTest() builder (after)
/// CHECK-NOT: NullCheck
public Main newInstanceRemoveTest() {
Main m = new Main();
@@ -54,13 +48,10 @@
/// CHECK-START: Main Main.newArrayRemoveTest() builder (after)
/// CHECK: NewArray
- /// CHECK: NullCheck
/// CHECK: ArrayGet
- /// CHECK-START: Main Main.newArrayRemoveTest() instruction_simplifier (after)
- /// CHECK: NewArray
+ /// CHECK-START: Main Main.newArrayRemoveTest() builder (after)
/// CHECK-NOT: NullCheck
- /// CHECK: ArrayGet
public Main newArrayRemoveTest() {
Main[] ms = new Main[1];
return ms[0];
@@ -179,9 +170,6 @@
}
/// CHECK-START: Main Main.scopeRemoveTest(int, Main) builder (after)
- /// CHECK: NullCheck
-
- /// CHECK-START: Main Main.scopeRemoveTest(int, Main) instruction_simplifier (after)
/// CHECK-NOT: NullCheck
public Main scopeRemoveTest(int count, Main a) {
Main m = null;
diff --git a/test/572-checker-array-get-regression/src/Main.java b/test/572-checker-array-get-regression/src/Main.java
index b55be70..89b97ed 100644
--- a/test/572-checker-array-get-regression/src/Main.java
+++ b/test/572-checker-array-get-regression/src/Main.java
@@ -25,13 +25,11 @@
/// CHECK-DAG: <<Const2P19:i\d+>> IntConstant 524288
/// CHECK-DAG: <<ConstM1:i\d+>> IntConstant -1
/// CHECK-DAG: <<Array:l\d+>> NewArray [<<Const2P19>>,<<Method>>]
- /// CHECK-DAG: <<NullCheck1:l\d+>> NullCheck [<<Array>>]
- /// CHECK-DAG: <<Length1:i\d+>> ArrayLength [<<NullCheck1>>]
+ /// CHECK-DAG: <<Length1:i\d+>> ArrayLength [<<Array>>]
/// CHECK-DAG: <<Index:i\d+>> Add [<<Length1>>,<<ConstM1>>]
- /// CHECK-DAG: <<NullCheck2:l\d+>> NullCheck [<<Array>>]
- /// CHECK-DAG: <<Length2:i\d+>> ArrayLength [<<NullCheck2>>]
+ /// CHECK-DAG: <<Length2:i\d+>> ArrayLength [<<Array>>]
/// CHECK-DAG: <<BoundsCheck:i\d+>> BoundsCheck [<<Index>>,<<Length2>>]
- /// CHECK-DAG: <<LastElement:l\d+>> ArrayGet [<<NullCheck2>>,<<BoundsCheck>>]
+ /// CHECK-DAG: <<LastElement:l\d+>> ArrayGet [<<Array>>,<<BoundsCheck>>]
/// CHECK-DAG: Return [<<LastElement>>]
