Optimize AOT's switchable calls for the monomorphic case.

runtime/vm/code_patcher_x64.cc

Index: runtime/vm/code_patcher_x64.cc
diff --git a/runtime/vm/code_patcher_x64.cc b/runtime/vm/code_patcher_x64.cc
index b8863dc721b87999568d37e2d1adbf56b3a37f1b..0e18f6f046672c96a3ed6ce8403c38999f1e7616 100644
--- a/runtime/vm/code_patcher_x64.cc
+++ b/runtime/vm/code_patcher_x64.cc
@@ -190,10 +190,11 @@ class PoolPointerCall : public ValueObject {
 };
 
 
-// Instance call that can switch from an IC call to a megamorphic call
-//   load ICData             load MegamorphicCache
-//   call ICLookup stub  ->  call MegamorphicLookup stub
-//   call target             call target
+// Instance call that can switch between a direct monomorphic call, an IC call,
+// and a megamorphic call.
+//   load guarded cid            load ICData             load MegamorphicCache
+//   load monomorphic target <-> load ICLookup stub  ->  load MMLookup stub
+//   call target.entry           call stub.entry         call stub.entry
 class SwitchableCall : public ValueObject {
  public:
   SwitchableCall(uword return_address, const Code& code)
@@ -202,39 +203,42 @@ class SwitchableCall : public ValueObject {
     ASSERT(IsValid());
   }
 
-  static const int kCallPatternSize = 24;
+  static const int kCallPatternSize = 21;
 
   bool IsValid() const {
     static int16_t pattern[kCallPatternSize] = {
       0x49, 0x8b, 0x9f, -1, -1, -1, -1,  // movq rbx, [PP + cache_offs]
       0x4d, 0x8b, 0xa7, -1, -1, -1, -1,  // movq r12, [PP + code_offs]
-      0x4d, 0x8b, 0x5c, 0x24, 0x07,      // movq r11, [r12 + entrypoint_off]
-      0x41, 0xff, 0xd3,                  // call r11
+      0x49, 0x8b, 0x4c, 0x24, 0x0f,      // movq rcx, [r12 + entrypoint_off]
       0xff, 0xd1,                        // call rcx
     };
+    ASSERT(ARRAY_SIZE(pattern) == kCallPatternSize);
     return MatchesPattern(start_, pattern, kCallPatternSize);
   }
 
-  intptr_t cache_index() const {
+  intptr_t data_index() const {
     return IndexFromPPLoad(start_ + 3);
   }
-  intptr_t lookup_stub_index() const {
+  intptr_t target_index() const {
     return IndexFromPPLoad(start_ + 10);
   }
 
-  RawObject* cache() const {
-    return object_pool_.ObjectAt(cache_index());
+  RawObject* data() const {
+    return object_pool_.ObjectAt(data_index());
+  }
+  RawCode* target() const {
+    return reinterpret_cast<RawCode*>(object_pool_.ObjectAt(target_index()));
   }
 
-  void SetCache(const MegamorphicCache& cache) const {
-    ASSERT(Object::Handle(object_pool_.ObjectAt(cache_index())).IsICData());
-    object_pool_.SetObjectAt(cache_index(), cache);
+  void SetData(const Object& data) const {
+    ASSERT(!Object::Handle(object_pool_.ObjectAt(data_index())).IsCode());
+    object_pool_.SetObjectAt(data_index(), data);
     // No need to flush the instruction cache, since the code is not modified.
   }
 
-  void SetLookupStub(const Code& lookup_stub) const {
-    ASSERT(Object::Handle(object_pool_.ObjectAt(lookup_stub_index())).IsCode());
-    object_pool_.SetObjectAt(lookup_stub_index(), lookup_stub);
+  void SetTarget(const Code& target) const {
+    ASSERT(Object::Handle(object_pool_.ObjectAt(target_index())).IsCode());
+    object_pool_.SetObjectAt(target_index(), target);
     // No need to flush the instruction cache, since the code is not modified.
   }
 
@@ -313,15 +317,29 @@ RawFunction* CodePatcher::GetUnoptimizedStaticCallAt(
 
 
 void CodePatcher::PatchSwitchableCallAt(uword return_address,
-                                        const Code& code,
-                                        const ICData& ic_data,
-                                        const MegamorphicCache& cache,
-                                        const Code& lookup_stub) {
-  ASSERT(code.ContainsInstructionAt(return_address));
-  SwitchableCall call(return_address, code);
-  ASSERT(call.cache() == ic_data.raw());
-  call.SetLookupStub(lookup_stub);
-  call.SetCache(cache);
+                                        const Code& caller_code,
+                                        const Object& data,
+                                        const Code& target) {
+  ASSERT(caller_code.ContainsInstructionAt(return_address));
+  SwitchableCall call(return_address, caller_code);
+  call.SetData(data);
+  call.SetTarget(target);
+}
+
+
+RawCode* CodePatcher::GetSwitchableCallTargetAt(uword return_address,
+                                                const Code& caller_code) {
+  ASSERT(caller_code.ContainsInstructionAt(return_address));
+  SwitchableCall call(return_address, caller_code);
+  return call.target();
+}
+
+
+RawObject* CodePatcher::GetSwitchableCallDataAt(uword return_address,
+                                                const Code& caller_code) {
+  ASSERT(caller_code.ContainsInstructionAt(return_address));
+  SwitchableCall call(return_address, caller_code);
+  return call.data();
 }