Optimize AOT's switchable calls for the monomorphic case.

runtime/vm/stub_code_arm64.cc

Index: runtime/vm/stub_code_arm64.cc
diff --git a/runtime/vm/stub_code_arm64.cc b/runtime/vm/stub_code_arm64.cc
index 9034730ce1e8222099062762239991b2287d8fad..09a38ebe41005293221c25657ae5290441c709ab 100644
--- a/runtime/vm/stub_code_arm64.cc
+++ b/runtime/vm/stub_code_arm64.cc
@@ -2036,6 +2036,8 @@ void StubCode::GenerateOptimizedIdenticalWithNumberCheckStub(
 //  CODE_REG: target Code
 //  R4: arguments descriptor
 void StubCode::GenerateMegamorphicLookupStub(Assembler* assembler) {
+  __ NoMonomorphicCheckedEntry();
+
   // Jump if receiver is a smi.
   Label smi_case;
   __ TestImmediate(R0, kSmiTagMask);
@@ -2083,7 +2085,7 @@ void StubCode::GenerateMegamorphicLookupStub(Assembler* assembler) {
   __ ldr(R4, FieldAddress(R5, MegamorphicCache::arguments_descriptor_offset()));
   __ ldr(R1, FieldAddress(R0, Function::entry_point_offset()));
   __ ldr(CODE_REG, FieldAddress(R0, Function::code_offset()));
-  __ ret();
+  __ br(R1);
 
   // Probe failed, check if it is a miss.
   __ Bind(&probe_failed);
@@ -2110,6 +2112,8 @@ void StubCode::GenerateMegamorphicLookupStub(Assembler* assembler) {
 //  CODE_REG: target Code object
 //  R4: arguments descriptor
 void StubCode::GenerateICLookupThroughFunctionStub(Assembler* assembler) {
+  __ NoMonomorphicCheckedEntry();
+
   Label loop, found, miss;
   __ ldr(R4, FieldAddress(R5, ICData::arguments_descriptor_offset()));
   __ ldr(R8, FieldAddress(R5, ICData::ic_data_offset()));
@@ -2134,17 +2138,19 @@ void StubCode::GenerateICLookupThroughFunctionStub(Assembler* assembler) {
   __ ldr(R0, Address(R8, target_offset));
   __ ldr(R1, FieldAddress(R0, Function::entry_point_offset()));
   __ ldr(CODE_REG, FieldAddress(R0, Function::code_offset()));
-  __ ret();
+  __ br(R1);
 
   __ Bind(&miss);
   __ LoadIsolate(R2);
   __ ldr(CODE_REG, Address(R2, Isolate::ic_miss_code_offset()));
   __ ldr(R1, FieldAddress(CODE_REG, Code::entry_point_offset()));
-  __ ret();
+  __ br(R1);
 }
 
 
 void StubCode::GenerateICLookupThroughCodeStub(Assembler* assembler) {
+  __ NoMonomorphicCheckedEntry();
+
   Label loop, found, miss;
   __ ldr(R4, FieldAddress(R5, ICData::arguments_descriptor_offset()));
   __ ldr(R8, FieldAddress(R5, ICData::ic_data_offset()));
@@ -2169,13 +2175,34 @@ void StubCode::GenerateICLookupThroughCodeStub(Assembler* assembler) {
   const intptr_t entry_offset = ICData::EntryPointIndexFor(1) * kWordSize;
   __ ldr(R1, Address(R8, entry_offset));
   __ ldr(CODE_REG, Address(R8, code_offset));
-  __ ret();
+  __ br(R1);
 
   __ Bind(&miss);
   __ LoadIsolate(R2);
   __ ldr(CODE_REG, Address(R2, Isolate::ic_miss_code_offset()));
   __ ldr(R1, FieldAddress(CODE_REG, Code::entry_point_offset()));
-  __ ret();
+  __ br(R1);
+}
+
+
+// Called from switchable IC calls.
+//  R0: receiver
+
+void StubCode::GenerateMonomorphicMissStub(Assembler* assembler) {
+  __ EnterStubFrame();
+  __ Push(R0);  // Preserve receiver.
+
+  __ PushObject(Object::null_object());  // Result.
+  __ Push(R0);                           // Arg0: Receiver / stub out
+  __ CallRuntime(kMonomorphicMissRuntimeEntry, 1);
+  __ Pop(CODE_REG);
+  __ Pop(R5);  // result = IC
+
+  __ Pop(R0);  // Restore receiver.
+  __ LeaveStubFrame();
+
+  __ ldr(R1, FieldAddress(CODE_REG, Code::checked_entry_point_offset()));
+  __ br(R1);
 }