Use PC-relative pointer to boot image methods.

In preparation for adding ArtMethod entries to the .bss
section, add direct PC-relative pointers to methods so that
the number of needed .bss entries for boot image is small.

Test: m test-art-host-gtest
Test: testrunner.py --host
Test: testrunner.py --target on Nexus 6P
Test: Nexus 6P boots.
Test: Build aosp_mips64-userdebug
Bug: 30627598
Change-Id: Ia89f5f9975b741ddac2816e1570077ba4b4c020f
diff --git a/compiler/compiled_method.h b/compiler/compiled_method.h
index 912c964..0ca23a5 100644
--- a/compiler/compiled_method.h
+++ b/compiler/compiled_method.h
@@ -119,7 +119,7 @@
   // choose to squeeze the Type into fewer than 8 bits, we'll have to declare
   // patch_type_ as an uintN_t and do explicit static_cast<>s.
   enum class Type : uint8_t {
-    kMethod,
+    kMethodRelative,          // NOTE: Actual patching is instruction_set-dependent.
     kCall,
     kCallRelative,            // NOTE: Actual patching is instruction_set-dependent.
     kTypeRelative,            // NOTE: Actual patching is instruction_set-dependent.
@@ -130,11 +130,13 @@
     kBakerReadBarrierBranch,  // NOTE: Actual patching is instruction_set-dependent.
   };
 
-  static LinkerPatch MethodPatch(size_t literal_offset,
-                                 const DexFile* target_dex_file,
-                                 uint32_t target_method_idx) {
-    LinkerPatch patch(literal_offset, Type::kMethod, target_dex_file);
+  static LinkerPatch RelativeMethodPatch(size_t literal_offset,
+                                         const DexFile* target_dex_file,
+                                         uint32_t pc_insn_offset,
+                                         uint32_t target_method_idx) {
+    LinkerPatch patch(literal_offset, Type::kMethodRelative, target_dex_file);
     patch.method_idx_ = target_method_idx;
+    patch.pc_insn_offset_ = pc_insn_offset;
     return patch;
   }
 
@@ -226,6 +228,7 @@
 
   bool IsPcRelative() const {
     switch (GetType()) {
+      case Type::kMethodRelative:
       case Type::kCallRelative:
       case Type::kTypeRelative:
       case Type::kTypeBssEntry:
@@ -240,7 +243,7 @@
   }
 
   MethodReference TargetMethod() const {
-    DCHECK(patch_type_ == Type::kMethod ||
+    DCHECK(patch_type_ == Type::kMethodRelative ||
            patch_type_ == Type::kCall ||
            patch_type_ == Type::kCallRelative);
     return MethodReference(target_dex_file_, method_idx_);
@@ -281,7 +284,8 @@
   }
 
   uint32_t PcInsnOffset() const {
-    DCHECK(patch_type_ == Type::kTypeRelative ||
+    DCHECK(patch_type_ == Type::kMethodRelative ||
+           patch_type_ == Type::kTypeRelative ||
            patch_type_ == Type::kTypeBssEntry ||
            patch_type_ == Type::kStringRelative ||
            patch_type_ == Type::kStringBssEntry ||