AOT: Single target stub.

runtime/vm/stub_code_x64.cc

Index: runtime/vm/stub_code_x64.cc
diff --git a/runtime/vm/stub_code_x64.cc b/runtime/vm/stub_code_x64.cc
index 329d3f16bbc46d8f653386059bec9d8901c8ae92..6620c5014965a28ef5bb5e68445b5399499427c8 100644
--- a/runtime/vm/stub_code_x64.cc
+++ b/runtime/vm/stub_code_x64.cc
@@ -2167,6 +2167,45 @@ void StubCode::GenerateICCallThroughCodeStub(Assembler* assembler) {
 }
 
 
+// Called from switchable IC calls.
+//  RDI: receiver
+//  RBX: SingleTargetCache
+// Passed to target::
+//  CODE_REG: target Code object
+void StubCode::GenerateSingleTargetCallStub(Assembler* assembler) {
+  __ NoMonomorphicCheckedEntry();
+
+  Label miss;
+  __ LoadClassIdMayBeSmi(RAX, RDI);
+  __ movq(R9, FieldAddress(RBX, SingleTargetCache::lower_limit_offset()));
+  __ movq(R10, FieldAddress(RBX, SingleTargetCache::upper_limit_offset()));
+  __ cmpq(RAX, R9);

[Florian Schneider, 2016/08/30 20:42:34]

Not sure if it's worth doing, but if upper_limit contains the difference between
the two (upper - lower), then you could do only one unsigned compare, like we do
for array bounds checks:

__ subq(RAX, R9);
__ cmpq(RAX, R10);
__ j(ABOVE, &miss);

[rmacnak, 2016/08/31 16:42:57]

I see -0.5% layout benchmark and +0.5% build benchmark, so I'll stick with base
and bound.

+  __ j(LESS, &miss, Assembler::kNearJump);
+  __ cmpq(RAX, R10);
+  __ j(GREATER, &miss, Assembler::kNearJump);
+  __ movq(RCX, FieldAddress(RBX, SingleTargetCache::entry_point_offset()));
+  __ movq(CODE_REG, FieldAddress(RBX, SingleTargetCache::target_offset()));
+  __ jmp(RCX);
+
+  __ Bind(&miss);
+  __ EnterStubFrame();
+  __ pushq(RDI);  // Preserve receiver.
+
+  __ PushObject(Object::null_object());  // Result.
+  __ pushq(RDI);                         // Arg0: Receiver
+  __ CallRuntime(kSingleTargetMissRuntimeEntry, 1);
+  __ popq(RBX);
+  __ popq(RBX);  // result = IC
+
+  __ popq(RDI);  // Restore receiver.
+  __ LeaveStubFrame();
+
+  __ movq(CODE_REG, Address(THR, Thread::ic_lookup_through_code_stub_offset()));
+  __ movq(RCX, FieldAddress(CODE_REG, Code::checked_entry_point_offset()));
+  __ jmp(RCX);
+}
+
+
 // Called from the monomorphic checked entry.
 //  RDI: receiver
 void StubCode::GenerateMonomorphicMissStub(Assembler* assembler) {