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/utils/string_reference.h b/compiler/utils/string_reference.h
index 72552f2..9e1058e 100644
--- a/compiler/utils/string_reference.h
+++ b/compiler/utils/string_reference.h
@@ -26,7 +26,7 @@
 
 class DexFile;
 
-// A string is uniquely located by its DexFile and the string_ids_ table index into that DexFile.
+// A string is located by its DexFile and the string_ids_ table index into that DexFile.
 struct StringReference {
   StringReference(const DexFile* file, uint32_t index) : dex_file(file), string_index(index) { }