Improve array index analysis in LSA.
This CL improves analysis on array index in load store analysis.
Test: m test-art-host
Test: m test-art-target
Test: m test-art-host-gtest-load_store_analysis_test
Change-Id: Id5e5aa8b396c68e082db95809659494107985fa2
diff --git a/compiler/optimizing/load_store_analysis.cc b/compiler/optimizing/load_store_analysis.cc
index f2ee345..5a8ac59 100644
--- a/compiler/optimizing/load_store_analysis.cc
+++ b/compiler/optimizing/load_store_analysis.cc
@@ -22,6 +22,117 @@
// The number of heap locations for most of the methods stays below this threshold.
constexpr size_t kMaxNumberOfHeapLocations = 32;
+// Check if array indices array[idx1 +/- CONST] and array[idx2] MAY alias.
+static bool BinaryOpAndIndexMayAlias(const HBinaryOperation* idx1, const HInstruction* idx2) {
+ DCHECK(idx1 != nullptr);
+ DCHECK(idx2 != nullptr);
+
+ if (!idx1->IsAdd() && !idx1->IsSub()) {
+ // We currently only support Add and Sub operations.
+ return true;
+ }
+
+ HConstant* cst = idx1->GetConstantRight();
+ if (cst == nullptr || cst->IsArithmeticZero()) {
+ return true;
+ }
+
+ if (idx1->GetLeastConstantLeft() == idx2) {
+ // for example, array[idx1 + 1] and array[idx1]
+ return false;
+ }
+
+ return true;
+}
+
+// Check if Add and Sub MAY alias when used as indices in arrays.
+static bool BinaryOpsMayAlias(const HBinaryOperation* idx1, const HBinaryOperation* idx2) {
+ DCHECK(idx1!= nullptr);
+ DCHECK(idx2 != nullptr);
+
+ HConstant* idx1_cst = idx1->GetConstantRight();
+ HInstruction* idx1_other = idx1->GetLeastConstantLeft();
+ HConstant* idx2_cst = idx2->GetConstantRight();
+ HInstruction* idx2_other = idx2->GetLeastConstantLeft();
+
+ if (idx1_cst == nullptr || idx1_other == nullptr ||
+ idx2_cst == nullptr || idx2_other == nullptr) {
+ // We only analyze patterns like [i +/- CONST].
+ return true;
+ }
+
+ if (idx1_other != idx2_other) {
+ // For example, [j+1] and [k+1] MAY alias.
+ return true;
+ }
+
+ if ((idx1->IsAdd() && idx2->IsAdd()) ||
+ (idx1->IsSub() && idx2->IsSub())) {
+ return idx1_cst->AsIntConstant()->GetValue() == idx2_cst->AsIntConstant()->GetValue();
+ }
+
+ if ((idx1->IsAdd() && idx2->IsSub()) ||
+ (idx1->IsSub() && idx2->IsAdd())) {
+ // [i + CONST1] and [i - CONST2] MAY alias iff CONST1 == -CONST2.
+ // By checking CONST1 == -CONST2, following cases are handled:
+ // - Zero constants case [i+0] and [i-0] is handled.
+ // - Overflow cases are handled, for example:
+ // [i+0x80000000] and [i-0x80000000];
+ // [i+0x10] and [i-0xFFFFFFF0].
+ // - Other cases [i+CONST1] and [i-CONST2] without any overflow is handled.
+ return idx1_cst->AsIntConstant()->GetValue() == -(idx2_cst->AsIntConstant()->GetValue());
+ }
+
+ // All other cases, MAY alias.
+ return true;
+}
+
+// The following array index cases are handled:
+// [i] and [i]
+// [CONST1] and [CONST2]
+// [i] and [i+CONST]
+// [i] and [i-CONST]
+// [i+CONST1] and [i+CONST2]
+// [i-CONST1] and [i-CONST2]
+// [i+CONST1] and [i-CONST2]
+// [i-CONST1] and [i+CONST2]
+// For other complicated cases, we rely on other passes like GVN and simpilfier
+// to optimize these cases before this pass.
+// For example: [i+j+k+10] and [i+k+10+j] shall be optimized to [i7+10] and [i7+10].
+bool HeapLocationCollector::CanArrayIndicesAlias(const HInstruction* idx1,
+ const HInstruction* idx2) const {
+ DCHECK(idx1 != nullptr);
+ DCHECK(idx2 != nullptr);
+
+ if (idx1 == idx2) {
+ // [i] and [i]
+ return true;
+ }
+ if (idx1->IsIntConstant() && idx2->IsIntConstant()) {
+ // [CONST1] and [CONST2]
+ return idx1->AsIntConstant()->GetValue() == idx2->AsIntConstant()->GetValue();
+ }
+
+ if (idx1->IsBinaryOperation() && !BinaryOpAndIndexMayAlias(idx1->AsBinaryOperation(), idx2)) {
+ // [i] and [i+/-CONST]
+ return false;
+ }
+ if (idx2->IsBinaryOperation() && !BinaryOpAndIndexMayAlias(idx2->AsBinaryOperation(), idx1)) {
+ // [i+/-CONST] and [i]
+ return false;
+ }
+
+ if (idx1->IsBinaryOperation() && idx2->IsBinaryOperation()) {
+ // [i+/-CONST1] and [i+/-CONST2]
+ if (!BinaryOpsMayAlias(idx1->AsBinaryOperation(), idx2->AsBinaryOperation())) {
+ return false;
+ }
+ }
+
+ // By default, MAY alias.
+ return true;
+}
+
void LoadStoreAnalysis::Run() {
for (HBasicBlock* block : graph_->GetReversePostOrder()) {
heap_location_collector_.VisitBasicBlock(block);
diff --git a/compiler/optimizing/load_store_analysis.h b/compiler/optimizing/load_store_analysis.h
index 4e940f3..86fb8e0 100644
--- a/compiler/optimizing/load_store_analysis.h
+++ b/compiler/optimizing/load_store_analysis.h
@@ -214,6 +214,17 @@
return nullptr;
}
+ size_t GetArrayAccessHeapLocation(HInstruction* array, HInstruction* index) const {
+ DCHECK(array != nullptr);
+ DCHECK(index != nullptr);
+ HInstruction* original_ref = HuntForOriginalReference(array);
+ ReferenceInfo* ref_info = FindReferenceInfoOf(original_ref);
+ return FindHeapLocationIndex(ref_info,
+ HeapLocation::kInvalidFieldOffset,
+ index,
+ HeapLocation::kDeclaringClassDefIndexForArrays);
+ }
+
bool HasHeapStores() const {
return has_heap_stores_;
}
@@ -300,6 +311,8 @@
return true;
}
+ bool CanArrayIndicesAlias(const HInstruction* i1, const HInstruction* i2) const;
+
// `index1` and `index2` are indices in the array of collected heap locations.
// Returns the position in the bit vector that tracks whether the two heap
// locations may alias.
@@ -336,12 +349,7 @@
if (loc1->IsArrayElement() && loc2->IsArrayElement()) {
HInstruction* array_index1 = loc1->GetIndex();
HInstruction* array_index2 = loc2->GetIndex();
- DCHECK(array_index1 != nullptr);
- DCHECK(array_index2 != nullptr);
- if (array_index1->IsIntConstant() &&
- array_index2->IsIntConstant() &&
- array_index1->AsIntConstant()->GetValue() != array_index2->AsIntConstant()->GetValue()) {
- // Different constant indices do not alias.
+ if (!CanArrayIndicesAlias(array_index1, array_index2)) {
return false;
}
ReferenceInfo* ref_info = loc1->GetReferenceInfo();
diff --git a/compiler/optimizing/load_store_analysis_test.cc b/compiler/optimizing/load_store_analysis_test.cc
index 2418777..81344b5 100644
--- a/compiler/optimizing/load_store_analysis_test.cc
+++ b/compiler/optimizing/load_store_analysis_test.cc
@@ -184,4 +184,198 @@
ASSERT_FALSE(heap_location_collector.MayAlias(loc1, loc2));
}
+TEST_F(LoadStoreAnalysisTest, ArrayIndexAliasingTest) {
+ HBasicBlock* entry = new (&allocator_) HBasicBlock(graph_);
+ graph_->AddBlock(entry);
+ graph_->SetEntryBlock(entry);
+ graph_->BuildDominatorTree();
+
+ HInstruction* array = new (&allocator_) HParameterValue(
+ graph_->GetDexFile(), dex::TypeIndex(0), 0, Primitive::kPrimNot);
+ HInstruction* index = new (&allocator_) HParameterValue(
+ graph_->GetDexFile(), dex::TypeIndex(1), 1, Primitive::kPrimInt);
+ HInstruction* c0 = graph_->GetIntConstant(0);
+ HInstruction* c1 = graph_->GetIntConstant(1);
+ HInstruction* c_neg1 = graph_->GetIntConstant(-1);
+ HInstruction* add0 = new (&allocator_) HAdd(Primitive::kPrimInt, index, c0);
+ HInstruction* add1 = new (&allocator_) HAdd(Primitive::kPrimInt, index, c1);
+ HInstruction* sub0 = new (&allocator_) HSub(Primitive::kPrimInt, index, c0);
+ HInstruction* sub1 = new (&allocator_) HSub(Primitive::kPrimInt, index, c1);
+ HInstruction* sub_neg1 = new (&allocator_) HSub(Primitive::kPrimInt, index, c_neg1);
+ HInstruction* rev_sub1 = new (&allocator_) HSub(Primitive::kPrimInt, c1, index);
+ HInstruction* arr_set1 = new (&allocator_) HArraySet(array, c0, c0, Primitive::kPrimInt, 0);
+ HInstruction* arr_set2 = new (&allocator_) HArraySet(array, c1, c0, Primitive::kPrimInt, 0);
+ HInstruction* arr_set3 = new (&allocator_) HArraySet(array, add0, c0, Primitive::kPrimInt, 0);
+ HInstruction* arr_set4 = new (&allocator_) HArraySet(array, add1, c0, Primitive::kPrimInt, 0);
+ HInstruction* arr_set5 = new (&allocator_) HArraySet(array, sub0, c0, Primitive::kPrimInt, 0);
+ HInstruction* arr_set6 = new (&allocator_) HArraySet(array, sub1, c0, Primitive::kPrimInt, 0);
+ HInstruction* arr_set7 = new (&allocator_) HArraySet(array, rev_sub1, c0, Primitive::kPrimInt, 0);
+ HInstruction* arr_set8 = new (&allocator_) HArraySet(array, sub_neg1, c0, Primitive::kPrimInt, 0);
+
+ entry->AddInstruction(array);
+ entry->AddInstruction(index);
+ entry->AddInstruction(add0);
+ entry->AddInstruction(add1);
+ entry->AddInstruction(sub0);
+ entry->AddInstruction(sub1);
+ entry->AddInstruction(sub_neg1);
+ entry->AddInstruction(rev_sub1);
+
+ entry->AddInstruction(arr_set1); // array[0] = c0
+ entry->AddInstruction(arr_set2); // array[1] = c0
+ entry->AddInstruction(arr_set3); // array[i+0] = c0
+ entry->AddInstruction(arr_set4); // array[i+1] = c0
+ entry->AddInstruction(arr_set5); // array[i-0] = c0
+ entry->AddInstruction(arr_set6); // array[i-1] = c0
+ entry->AddInstruction(arr_set7); // array[1-i] = c0
+ entry->AddInstruction(arr_set8); // array[i-(-1)] = c0
+
+ LoadStoreAnalysis lsa(graph_);
+ lsa.Run();
+ const HeapLocationCollector& heap_location_collector = lsa.GetHeapLocationCollector();
+
+ // LSA/HeapLocationCollector should see those ArrayGet instructions.
+ ASSERT_EQ(heap_location_collector.GetNumberOfHeapLocations(), 8U);
+ ASSERT_TRUE(heap_location_collector.HasHeapStores());
+
+ // Test queries on HeapLocationCollector's aliasing matrix after load store analysis.
+ size_t loc1 = HeapLocationCollector::kHeapLocationNotFound;
+ size_t loc2 = HeapLocationCollector::kHeapLocationNotFound;
+
+ // Test alias: array[0] and array[1]
+ loc1 = heap_location_collector.GetArrayAccessHeapLocation(array, c0);
+ loc2 = heap_location_collector.GetArrayAccessHeapLocation(array, c1);
+ ASSERT_FALSE(heap_location_collector.MayAlias(loc1, loc2));
+
+ // Test alias: array[i+0] and array[i-0]
+ loc1 = heap_location_collector.GetArrayAccessHeapLocation(array, add0);
+ loc2 = heap_location_collector.GetArrayAccessHeapLocation(array, sub0);
+ ASSERT_TRUE(heap_location_collector.MayAlias(loc1, loc2));
+
+ // Test alias: array[i+1] and array[i-1]
+ loc1 = heap_location_collector.GetArrayAccessHeapLocation(array, add1);
+ loc2 = heap_location_collector.GetArrayAccessHeapLocation(array, sub1);
+ ASSERT_FALSE(heap_location_collector.MayAlias(loc1, loc2));
+
+ // Test alias: array[i+1] and array[1-i]
+ loc1 = heap_location_collector.GetArrayAccessHeapLocation(array, add1);
+ loc2 = heap_location_collector.GetArrayAccessHeapLocation(array, rev_sub1);
+ ASSERT_TRUE(heap_location_collector.MayAlias(loc1, loc2));
+
+ // Test alias: array[i+1] and array[i-(-1)]
+ loc1 = heap_location_collector.GetArrayAccessHeapLocation(array, add1);
+ loc2 = heap_location_collector.GetArrayAccessHeapLocation(array, sub_neg1);
+ ASSERT_TRUE(heap_location_collector.MayAlias(loc1, loc2));
+}
+
+TEST_F(LoadStoreAnalysisTest, ArrayIndexCalculationOverflowTest) {
+ HBasicBlock* entry = new (&allocator_) HBasicBlock(graph_);
+ graph_->AddBlock(entry);
+ graph_->SetEntryBlock(entry);
+ graph_->BuildDominatorTree();
+
+ HInstruction* array = new (&allocator_) HParameterValue(
+ graph_->GetDexFile(), dex::TypeIndex(0), 0, Primitive::kPrimNot);
+ HInstruction* index = new (&allocator_) HParameterValue(
+ graph_->GetDexFile(), dex::TypeIndex(1), 1, Primitive::kPrimInt);
+
+ HInstruction* c0 = graph_->GetIntConstant(0);
+ HInstruction* c_0x80000000 = graph_->GetIntConstant(0x80000000);
+ HInstruction* c_0x10 = graph_->GetIntConstant(0x10);
+ HInstruction* c_0xFFFFFFF0 = graph_->GetIntConstant(0xFFFFFFF0);
+ HInstruction* c_0x7FFFFFFF = graph_->GetIntConstant(0x7FFFFFFF);
+ HInstruction* c_0x80000001 = graph_->GetIntConstant(0x80000001);
+
+ // `index+0x80000000` and `index-0x80000000` array indices MAY alias.
+ HInstruction* add_0x80000000 = new (&allocator_) HAdd(Primitive::kPrimInt, index, c_0x80000000);
+ HInstruction* sub_0x80000000 = new (&allocator_) HSub(Primitive::kPrimInt, index, c_0x80000000);
+ HInstruction* arr_set_1 = new (&allocator_) HArraySet(
+ array, add_0x80000000, c0, Primitive::kPrimInt, 0);
+ HInstruction* arr_set_2 = new (&allocator_) HArraySet(
+ array, sub_0x80000000, c0, Primitive::kPrimInt, 0);
+
+ // `index+0x10` and `index-0xFFFFFFF0` array indices MAY alias.
+ HInstruction* add_0x10 = new (&allocator_) HAdd(Primitive::kPrimInt, index, c_0x10);
+ HInstruction* sub_0xFFFFFFF0 = new (&allocator_) HSub(Primitive::kPrimInt, index, c_0xFFFFFFF0);
+ HInstruction* arr_set_3 = new (&allocator_) HArraySet(
+ array, add_0x10, c0, Primitive::kPrimInt, 0);
+ HInstruction* arr_set_4 = new (&allocator_) HArraySet(
+ array, sub_0xFFFFFFF0, c0, Primitive::kPrimInt, 0);
+
+ // `index+0x7FFFFFFF` and `index-0x80000001` array indices MAY alias.
+ HInstruction* add_0x7FFFFFFF = new (&allocator_) HAdd(Primitive::kPrimInt, index, c_0x7FFFFFFF);
+ HInstruction* sub_0x80000001 = new (&allocator_) HSub(Primitive::kPrimInt, index, c_0x80000001);
+ HInstruction* arr_set_5 = new (&allocator_) HArraySet(
+ array, add_0x7FFFFFFF, c0, Primitive::kPrimInt, 0);
+ HInstruction* arr_set_6 = new (&allocator_) HArraySet(
+ array, sub_0x80000001, c0, Primitive::kPrimInt, 0);
+
+ // `index+0` and `index-0` array indices MAY alias.
+ HInstruction* add_0 = new (&allocator_) HAdd(Primitive::kPrimInt, index, c0);
+ HInstruction* sub_0 = new (&allocator_) HSub(Primitive::kPrimInt, index, c0);
+ HInstruction* arr_set_7 = new (&allocator_) HArraySet(array, add_0, c0, Primitive::kPrimInt, 0);
+ HInstruction* arr_set_8 = new (&allocator_) HArraySet(array, sub_0, c0, Primitive::kPrimInt, 0);
+
+ entry->AddInstruction(array);
+ entry->AddInstruction(index);
+ entry->AddInstruction(add_0x80000000);
+ entry->AddInstruction(sub_0x80000000);
+ entry->AddInstruction(add_0x10);
+ entry->AddInstruction(sub_0xFFFFFFF0);
+ entry->AddInstruction(add_0x7FFFFFFF);
+ entry->AddInstruction(sub_0x80000001);
+ entry->AddInstruction(add_0);
+ entry->AddInstruction(sub_0);
+ entry->AddInstruction(arr_set_1);
+ entry->AddInstruction(arr_set_2);
+ entry->AddInstruction(arr_set_3);
+ entry->AddInstruction(arr_set_4);
+ entry->AddInstruction(arr_set_5);
+ entry->AddInstruction(arr_set_6);
+ entry->AddInstruction(arr_set_7);
+ entry->AddInstruction(arr_set_8);
+
+ LoadStoreAnalysis lsa(graph_);
+ lsa.Run();
+ const HeapLocationCollector& heap_location_collector = lsa.GetHeapLocationCollector();
+
+ // LSA/HeapLocationCollector should see those ArrayGet instructions.
+ ASSERT_EQ(heap_location_collector.GetNumberOfHeapLocations(), 8U);
+ ASSERT_TRUE(heap_location_collector.HasHeapStores());
+
+ // Test queries on HeapLocationCollector's aliasing matrix after load store analysis.
+ size_t loc1 = HeapLocationCollector::kHeapLocationNotFound;
+ size_t loc2 = HeapLocationCollector::kHeapLocationNotFound;
+
+ // Test alias: array[i+0x80000000] and array[i-0x80000000]
+ loc1 = heap_location_collector.GetArrayAccessHeapLocation(array, add_0x80000000);
+ loc2 = heap_location_collector.GetArrayAccessHeapLocation(array, sub_0x80000000);
+ ASSERT_TRUE(heap_location_collector.MayAlias(loc1, loc2));
+
+ // Test alias: array[i+0x10] and array[i-0xFFFFFFF0]
+ loc1 = heap_location_collector.GetArrayAccessHeapLocation(array, add_0x10);
+ loc2 = heap_location_collector.GetArrayAccessHeapLocation(array, sub_0xFFFFFFF0);
+ ASSERT_TRUE(heap_location_collector.MayAlias(loc1, loc2));
+
+ // Test alias: array[i+0x7FFFFFFF] and array[i-0x80000001]
+ loc1 = heap_location_collector.GetArrayAccessHeapLocation(array, add_0x7FFFFFFF);
+ loc2 = heap_location_collector.GetArrayAccessHeapLocation(array, sub_0x80000001);
+ ASSERT_TRUE(heap_location_collector.MayAlias(loc1, loc2));
+
+ // Test alias: array[i+0] and array[i-0]
+ loc1 = heap_location_collector.GetArrayAccessHeapLocation(array, add_0);
+ loc2 = heap_location_collector.GetArrayAccessHeapLocation(array, sub_0);
+ ASSERT_TRUE(heap_location_collector.MayAlias(loc1, loc2));
+
+ // Should not alias:
+ loc1 = heap_location_collector.GetArrayAccessHeapLocation(array, sub_0x80000000);
+ loc2 = heap_location_collector.GetArrayAccessHeapLocation(array, sub_0x80000001);
+ ASSERT_FALSE(heap_location_collector.MayAlias(loc1, loc2));
+
+ // Should not alias:
+ loc1 = heap_location_collector.GetArrayAccessHeapLocation(array, add_0);
+ loc2 = heap_location_collector.GetArrayAccessHeapLocation(array, sub_0x80000000);
+ ASSERT_FALSE(heap_location_collector.MayAlias(loc1, loc2));
+}
+
} // namespace art