From 6f40f3867459b66ec315dd4f70f4474171065aab Mon Sep 17 00:00:00 2001
From: Lokesh Gidra <lokeshgidra@google.com>
Date: Thu, 27 Jun 2024 20:20:04 +0000
Subject: Use variable sized ref-offset bitmap for fast VisitReferences()

Bug: 304325190
Test: art/test/testrunner/testrunner.py --host
Change-Id: I6e25143b827acaa12ff5bd94e6196faaed461f4a
---
 runtime/class_linker.cc | 38 ++++++--------------------------------
 1 file changed, 6 insertions(+), 32 deletions(-)

(limited to 'runtime/class_linker.cc')

diff --git a/runtime/class_linker.cc b/runtime/class_linker.cc
index d0fdcf0c25..dd78be3105 100644
--- a/runtime/class_linker.cc
+++ b/runtime/class_linker.cc
@@ -3686,13 +3686,14 @@ uint32_t ClassLinker::SizeOfClassWithoutEmbeddedTables(const DexFile& dex_file,
         UNREACHABLE();
     }
   }
-  return mirror::Class::ComputeClassSize(false,
-                                         0,
+  return mirror::Class::ComputeClassSize(/*has_embedded_vtable=*/false,
+                                         /*num_vtable_entries=*/0,
                                          num_8,
                                          num_16,
                                          num_32,
                                          num_64,
                                          num_ref,
+                                         /*num_ref_bitmap_entries=*/0,
                                          image_pointer_size_);
 }
 
@@ -6335,7 +6336,8 @@ bool ClassLinker::LinkClass(Thread* self,
   if (!LinkStaticFields(self, klass, &class_size)) {
     return false;
   }
-  CreateReferenceInstanceOffsets(klass);
+  class_size =
+      mirror::Class::AdjustClassSizeForReferenceOffsetBitmapDuringLinking(klass.Get(), class_size);
   CHECK_EQ(ClassStatus::kLoaded, klass->GetStatus());
 
   ImTable* imt = nullptr;
@@ -6377,6 +6379,7 @@ bool ClassLinker::LinkClass(Thread* self,
 
     if (klass->ShouldHaveEmbeddedVTable()) {
       klass->PopulateEmbeddedVTable(image_pointer_size_);
+      klass->PopulateReferenceOffsetBitmap();
     }
     if (klass->ShouldHaveImt()) {
       klass->SetImt(imt, image_pointer_size_);
@@ -9882,35 +9885,6 @@ bool ClassLinker::VerifyRecordClass(Handle<mirror::Class> klass, ObjPtr<mirror::
   return true;
 }
 
-//  Set the bitmap of reference instance field offsets.
-void ClassLinker::CreateReferenceInstanceOffsets(Handle<mirror::Class> klass) {
-  uint32_t reference_offsets = 0;
-  ObjPtr<mirror::Class> super_class = klass->GetSuperClass();
-  // Leave the reference offsets as 0 for mirror::Object (the class field is handled specially).
-  if (super_class != nullptr) {
-    reference_offsets = super_class->GetReferenceInstanceOffsets();
-    // Compute reference offsets unless our superclass overflowed.
-    if (reference_offsets != mirror::Class::kClassWalkSuper) {
-      size_t num_reference_fields = klass->NumReferenceInstanceFieldsDuringLinking();
-      if (num_reference_fields != 0u) {
-        // All of the fields that contain object references are guaranteed be grouped in memory
-        // starting at an appropriately aligned address after super class object data.
-        uint32_t start_offset = RoundUp(super_class->GetObjectSize(),
-                                        sizeof(mirror::HeapReference<mirror::Object>));
-        uint32_t start_bit = (start_offset - mirror::kObjectHeaderSize) /
-            sizeof(mirror::HeapReference<mirror::Object>);
-        if (start_bit + num_reference_fields > 32) {
-          reference_offsets = mirror::Class::kClassWalkSuper;
-        } else {
-          reference_offsets |= (0xffffffffu << start_bit) &
-                               (0xffffffffu >> (32 - (start_bit + num_reference_fields)));
-        }
-      }
-    }
-  }
-  klass->SetReferenceInstanceOffsets(reference_offsets);
-}
-
 ObjPtr<mirror::String> ClassLinker::DoResolveString(dex::StringIndex string_idx,
                                                     ObjPtr<mirror::DexCache> dex_cache) {
   StackHandleScope<1> hs(Thread::Current());
-- 
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