Optimizing: Improve const-string code generation.

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

For aosp_flounder-userdebug:
  - 32-bit boot.oat: -692KiB (-0.9%)
  - 64-bit boot.oat: -948KiB (-1.1%)
  - 32-bit dalvik cache total: -900KiB (-0.9%)
  - 64-bit dalvik cache total: -3672KiB (-1.5%)
    (contains more files than the 32-bit dalvik cache)
For aosp_flounder-userdebug forced to compile PIC:
  - 32-bit boot.oat: -380KiB (-0.5%)
  - 64-bit boot.oat: -928KiB (-1.0%)
  - 32-bit dalvik cache total: -468KiB (-0.4%)
  - 64-bit dalvik cache total: -1928KiB (-0.8%)
    (contains more files than the 32-bit dalvik cache)

Bug: 26884697
Change-Id: Iec7266ce67e6fedc107be78fab2e742a8dab2696

1 files changed, 17 insertions, 0 deletions

diff --git a/compiler/optimizing/code_generator.h b/compiler/optimizing/code_generator.h
index e56323ff0f..cad55296bc 100644
--- a/compiler/optimizing/code_generator.h
+++ b/compiler/optimizing/code_generator.h
@@ -443,6 +443,11 @@ class CodeGenerator {
                              uint32_t dex_pc,
                              SlowPathCode* slow_path) = 0;
 
+  // Check if the desired_string_load_kind is supported. If it is, return it,
+  // otherwise return a fall-back info that should be used instead.
+  virtual HLoadString::LoadKind GetSupportedLoadStringKind(
+      HLoadString::LoadKind desired_string_load_kind) = 0;
+
   // Check if the desired_dispatch_info is supported. If it is, return it,
   // otherwise return a fall-back info that should be used instead.
   virtual HInvokeStaticOrDirect::DispatchInfo GetSupportedInvokeStaticOrDirectDispatch(
@@ -471,6 +476,18 @@ class CodeGenerator {
     LabelType label;
   };
 
+  // String patch info used for recording locations of required linker patches and
+  // target strings. The actual string address can be absolute or PC-relative.
+  template <typename LabelType>
+  struct StringPatchInfo {
+    StringPatchInfo(const DexFile& df, uint32_t index)
+        : dex_file(df), string_index(index), label() { }
+
+    const DexFile& dex_file;
+    uint32_t string_index;
+    LabelType label;
+  };
+
   CodeGenerator(HGraph* graph,
                 size_t number_of_core_registers,
                 size_t number_of_fpu_registers,