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/pc_relative_fixups_x86.cc b/compiler/optimizing/pc_relative_fixups_x86.cc
index cb2fc0a..93116f8 100644
--- a/compiler/optimizing/pc_relative_fixups_x86.cc
+++ b/compiler/optimizing/pc_relative_fixups_x86.cc
@@ -80,6 +80,15 @@
     HandleInvoke(invoke);
   }
 
+  void VisitLoadClass(HLoadClass* load_class) OVERRIDE {
+    HLoadClass::LoadKind load_kind = load_class->GetLoadKind();
+    if (load_kind == HLoadClass::LoadKind::kBootImageLinkTimePcRelative ||
+        load_kind == HLoadClass::LoadKind::kDexCachePcRelative) {
+      InitializePCRelativeBasePointer();
+      load_class->AddSpecialInput(base_);
+    }
+  }
+
   void VisitLoadString(HLoadString* load_string) OVERRIDE {
     HLoadString::LoadKind load_kind = load_string->GetLoadKind();
     if (load_kind == HLoadString::LoadKind::kBootImageLinkTimePcRelative ||