Megamorphic code cleanup.

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 072d5c6b7fc2a76dd6e87403ad71cb47269442a4..997c24684c07bf6de3075d92cb91a254948c27cc 100644
--- a/runtime/vm/stub_code_arm64.cc
+++ b/runtime/vm/stub_code_arm64.cc
@@ -2098,52 +2098,6 @@ void StubCode::GenerateOptimizedIdenticalWithNumberCheckStub(
 }
 
 
-void StubCode::EmitMegamorphicLookup(Assembler* assembler) {
-  __ LoadTaggedClassIdMayBeSmi(R0, R0);
-  // R0: class ID of the receiver (smi).
-  __ ldr(R2, FieldAddress(R5, MegamorphicCache::buckets_offset()));
-  __ ldr(R1, FieldAddress(R5, MegamorphicCache::mask_offset()));
-  // R2: cache buckets array.
-  // R1: mask.
-
-  // Compute the table index.
-  ASSERT(MegamorphicCache::kSpreadFactor == 7);
-  // Use lsl and sub to multiply with 7 == 8 - 1.
-  __ LslImmediate(R3, R0, 3);
-  __ sub(R3, R3, Operand(R0));
-  // R3: probe.
-
-  Label loop, update, load_target_function;
-  __ b(&loop);
-
-  __ Bind(&update);
-  __ add(R3, R3, Operand(Smi::RawValue(1)));
-  __ Bind(&loop);
-  __ and_(R3, R3, Operand(R1));
-  const intptr_t base = Array::data_offset();
-  // R3 is smi tagged, but table entries are 16 bytes, so LSL 3.
-  __ add(TMP, R2, Operand(R3, LSL, 3));
-  __ ldr(R6, FieldAddress(TMP, base));
-
-  ASSERT(kIllegalCid == 0);
-  __ tst(R6, Operand(R6));
-  __ b(&load_target_function, EQ);
-  __ CompareRegisters(R6, R0);
-  __ b(&update, NE);
-
-  __ Bind(&load_target_function);
-  // Call the target found in the cache.  For a class id match, this is a
-  // proper target for the given name and arguments descriptor.  If the
-  // illegal class id was found, the target is a cache miss handler that can
-  // be invoked as a normal Dart function.
-  __ add(TMP, R2, Operand(R3, LSL, 3));
-  __ ldr(R0, FieldAddress(TMP, base + kWordSize));
-  __ ldr(R4, FieldAddress(R5, MegamorphicCache::arguments_descriptor_offset()));
-  __ ldr(R1, FieldAddress(R0, Function::entry_point_offset()));
-  __ ldr(CODE_REG, FieldAddress(R0, Function::code_offset()));
-}
-
-
 // Called from megamorphic calls.
 //  R0: receiver
 //  R5: MegamorphicCache (preserved)
@@ -2152,13 +2106,25 @@ void StubCode::EmitMegamorphicLookup(Assembler* assembler) {
 //  CODE_REG: target Code
 //  R4: arguments descriptor
 void StubCode::GenerateMegamorphicLookupStub(Assembler* assembler) {
-  __ LoadTaggedClassIdMayBeSmi(R0, R0);
-  // R0: class ID of the receiver (smi).
+  // Jump if receiver is a smi.
+  Label smi_case;
+  __ TestImmediate(R0, kSmiTagMask);
+  __ b(&smi_case, EQ);
+
+  // Loads the cid of the object.
+  __ LoadClassId(R0, R0);
+
+  Label cid_loaded;
+  __ Bind(&cid_loaded);
   __ ldr(R2, FieldAddress(R5, MegamorphicCache::buckets_offset()));
   __ ldr(R1, FieldAddress(R5, MegamorphicCache::mask_offset()));
   // R2: cache buckets array.
   // R1: mask.
 
+  // Make the cid into a smi.
+  __ SmiTag(R0);
+  // R0: class ID of the receiver (smi).
+
   // Compute the table index.
   ASSERT(MegamorphicCache::kSpreadFactor == 7);
   // Use lsl and sub to multiply with 7 == 8 - 1.
@@ -2198,6 +2164,11 @@ void StubCode::GenerateMegamorphicLookupStub(Assembler* assembler) {
   // Try next extry in the table.
   __ AddImmediate(R3, R3, Smi::RawValue(1));
   __ b(&loop);
+
+  // Load cid for the Smi case.
+  __ Bind(&smi_case);
+  __ LoadImmediate(R0, kSmiCid);
+  __ b(&cid_loaded);
 }