Improve HLoadClass code generation.

For classes in the boot image, use either direct pointers
or PC-relative addresses. For other classes, use PC-relative
access to the dex cache arrays for AOT and direct address of
the type's dex cache slot for JIT.

For aosp_flounder-userdebug:
  - 32-bit boot.oat: -252KiB (-0.3%)
  - 64-bit boot.oat: -412KiB (-0.4%)
  - 32-bit dalvik cache total: -392KiB (-0.4%)
  - 64-bit dalvik-cache total: -2312KiB (-1.0%)
    (contains more files than the 32-bit dalvik cache)
For aosp_flounder-userdebug forced to compile PIC:
  - 32-bit boot.oat: -124KiB (-0.2%)
  - 64-bit boot.oat: -420KiB (-0.5%)
  - 32-bit dalvik cache total: -136KiB (-0.1%)
  - 64-bit dalvik-cache total: -1136KiB (-0.5%)
    (contains more files than the 32-bit dalvik cache)

Bug: 27950288
Change-Id: I4da991a4b7e53c63c92558b97923d18092acf139
diff --git a/compiler/optimizing/dex_cache_array_fixups_arm.cc b/compiler/optimizing/dex_cache_array_fixups_arm.cc
index e9072b9..14c318e 100644
--- a/compiler/optimizing/dex_cache_array_fixups_arm.cc
+++ b/compiler/optimizing/dex_cache_array_fixups_arm.cc
@@ -44,8 +44,23 @@
   }
 
  private:
+  void VisitLoadClass(HLoadClass* load_class) OVERRIDE {
+    // If this is a load with PC-relative access to the dex cache types array,
+    // we need to add the dex cache arrays base as the special input.
+    if (load_class->GetLoadKind() == HLoadClass::LoadKind::kDexCachePcRelative) {
+      // Initialize base for target dex file if needed.
+      const DexFile& dex_file = load_class->GetDexFile();
+      HArmDexCacheArraysBase* base = GetOrCreateDexCacheArrayBase(dex_file);
+      // Update the element offset in base.
+      DexCacheArraysLayout layout(kArmPointerSize, &dex_file);
+      base->UpdateElementOffset(layout.TypeOffset(load_class->GetTypeIndex()));
+      // Add the special argument base to the load.
+      load_class->AddSpecialInput(base);
+    }
+  }
+
   void VisitLoadString(HLoadString* load_string) OVERRIDE {
-    // If this is a load with PC-relative access to the dex cache methods array,
+    // If this is a load with PC-relative access to the dex cache strings array,
     // we need to add the dex cache arrays base as the special input.
     if (load_string->GetLoadKind() == HLoadString::LoadKind::kDexCachePcRelative) {
       // Initialize base for target dex file if needed.