ARM64: Share address computation across SIMD LDRs/STRs.

For array accesses the element address has the following structure:
Address = CONST_OFFSET + base_addr + index << ELEM_SHIFT

Taking into account ARM64 LDR/STR addressing modes address part
(CONST_OFFSET + index << ELEM_SHIFT) can be shared across array
access with the same data type and index.

For example, for the following loop 5 accesses can share address
computation:

void foo(int[] a, int[] b, int[] c) {
  for (i...) {
    a[i] = a[i] + 5;
    b[i] = b[i] + c[i];
  }
}

Test: test-art-host, test-art-target

Change-Id: I46af3b4e4a55004336672cdba3296b7622d815ca

1 files changed, 57 insertions, 0 deletions

diff --git a/compiler/optimizing/instruction_simplifier_shared.cc b/compiler/optimizing/instruction_simplifier_shared.cc
index c39e5f4d3b..e5a8499ff4 100644
--- a/compiler/optimizing/instruction_simplifier_shared.cc
+++ b/compiler/optimizing/instruction_simplifier_shared.cc
@@ -16,6 +16,8 @@
 
 #include "instruction_simplifier_shared.h"
 
+#include "mirror/array-inl.h"
+
 namespace art {
 
 namespace {
@@ -346,4 +348,59 @@ bool TryCombineVecMultiplyAccumulate(HVecMul* mul, InstructionSet isa) {
   return false;
 }
 
+bool TryExtractVecArrayAccessAddress(HVecMemoryOperation* access, HInstruction* index) {
+  if (index->IsConstant()) {
+    // If index is constant the whole address calculation often can be done by LDR/STR themselves.
+    // TODO: Treat the case with not-embedable constant.
+    return false;
+  }
+
+  HGraph* graph = access->GetBlock()->GetGraph();
+  ArenaAllocator* arena = graph->GetArena();
+  Primitive::Type packed_type = access->GetPackedType();
+  uint32_t data_offset = mirror::Array::DataOffset(
+      Primitive::ComponentSize(packed_type)).Uint32Value();
+  size_t component_shift = Primitive::ComponentSizeShift(packed_type);
+
+  bool is_extracting_beneficial = false;
+  // It is beneficial to extract index intermediate address only if there are at least 2 users.
+  for (const HUseListNode<HInstruction*>& use : index->GetUses()) {
+    HInstruction* user = use.GetUser();
+    if (user->IsVecMemoryOperation() && user != access) {
+      HVecMemoryOperation* another_access = user->AsVecMemoryOperation();
+      Primitive::Type another_packed_type = another_access->GetPackedType();
+      uint32_t another_data_offset = mirror::Array::DataOffset(
+          Primitive::ComponentSize(another_packed_type)).Uint32Value();
+      size_t another_component_shift = Primitive::ComponentSizeShift(another_packed_type);
+      if (another_data_offset == data_offset && another_component_shift == component_shift) {
+        is_extracting_beneficial = true;
+        break;
+      }
+    } else if (user->IsIntermediateAddressIndex()) {
+      HIntermediateAddressIndex* another_access = user->AsIntermediateAddressIndex();
+      uint32_t another_data_offset = another_access->GetOffset()->AsIntConstant()->GetValue();
+      size_t another_component_shift = another_access->GetShift()->AsIntConstant()->GetValue();
+      if (another_data_offset == data_offset && another_component_shift == component_shift) {
+        is_extracting_beneficial = true;
+        break;
+      }
+    }
+  }
+
+  if (!is_extracting_beneficial) {
+    return false;
+  }
+
+  // Proceed to extract the index + data_offset address computation.
+  HIntConstant* offset = graph->GetIntConstant(data_offset);
+  HIntConstant* shift = graph->GetIntConstant(component_shift);
+  HIntermediateAddressIndex* address =
+      new (arena) HIntermediateAddressIndex(index, offset, shift, kNoDexPc);
+
+  access->GetBlock()->InsertInstructionBefore(address, access);
+  access->ReplaceInput(address, 1);
+
+  return true;
+}
+
 }  // namespace art