Cache lookups at megamorphic call sites in optimized code.

runtime/vm/flow_graph_compiler_ia32.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_IA32.
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "lib/error.h"
@@ skipping 1075 matching lines @@
   __ LoadObject(EDX, arguments_descriptor);
   GenerateDartCall(deopt_id,
                    token_pos,
                    target_label,
                    PcDescriptors::kIcCall,
                    locs);
   __ Drop(argument_count);
 }
 
 
+void FlowGraphCompiler::EmitMegamorphicInstanceCall(
+    const ICData& ic_data,
+    const Array& arguments_descriptor,
+    intptr_t argument_count,
+    intptr_t deopt_id,
+    intptr_t token_pos,
+    LocationSummary* locs) {
+  MegamorphicCacheTable* table = Isolate::Current()->megamorphic_cache_table();
+  const String& name = String::Handle(ic_data.target_name());
+  const MegamorphicCache& cache =
+      MegamorphicCache::ZoneHandle(table->Lookup(name, arguments_descriptor));
+  Label not_smi, load_cache;
+  __ movl(EAX, Address(ESP, (argument_count - 1) * kWordSize));
+  __ testl(EAX, Immediate(kSmiTagMask));
+  __ j(NOT_ZERO, &not_smi, Assembler::kNearJump);
+  __ movl(EAX, Immediate(Smi::RawValue(kSmiCid)));
+  __ jmp(&load_cache);
+
+  __ Bind(&not_smi);
+  __ LoadClassId(EAX, EAX);
+  __ SmiTag(EAX);
+
+  // EAX: class ID of the receiver (smi).
+  __ Bind(&load_cache);
+  __ LoadObject(EBX, cache);
+  __ movl(EDI, FieldAddress(EBX, MegamorphicCache::buckets_offset()));
+  __ movl(EBX, FieldAddress(EBX, MegamorphicCache::mask_offset()));
+  // EDI: cache buckets array.
+  // EBX: mask.
+  __ movl(ECX, EAX);
+
+  Label loop, update, found;
+  __ jmp(&loop);
+
+  __ Bind(&update);
+  __ addl(ECX, Immediate(Smi::RawValue(1)));
+  __ Bind(&loop);
+  __ andl(ECX, EBX);
+  const intptr_t base = Array::data_offset();
+  // ECX is smi tagged, but table entries are two words, so TIMES_4.
+  __ movl(EDX, FieldAddress(EDI, ECX, TIMES_4, base));
+
+  ASSERT(kIllegalCid == 0);
+  __ testl(EDX, EDX);
+  __ j(ZERO, &found, Assembler::kNearJump);

[srdjan, 2012/12/03 19:10:46]

Maybe use a different label e.g., megamorphic_miss, since kIllegalCid means that
there is no such cid in the cache.

Please document also how you are calling into the miss handler.

[Kevin Millikin (Google), 2012/12/06 14:03:11]

Changed to call_target.

+  __ cmpl(EDX, EAX);
+  __ j(NOT_EQUAL, &update, Assembler::kNearJump);
+
+  __ Bind(&found);
+  __ movl(EAX, FieldAddress(EDI, ECX, TIMES_4, base + kWordSize));
+  __ movl(EAX, FieldAddress(EAX, Function::code_offset()));
+  __ movl(EAX, FieldAddress(EAX, Code::instructions_offset()));
+  __ LoadObject(ECX, ic_data);
+  __ LoadObject(EDX, arguments_descriptor);
+  __ addl(EAX, Immediate(Instructions::HeaderSize() - kHeapObjectTag));
+  __ call(EAX);
+  AddCurrentDescriptor(PcDescriptors::kOther, Isolate::kNoDeoptId, token_pos);
+  RecordSafepoint(locs);
+  AddDeoptIndexAtCall(deopt_id, token_pos);
+  __ Drop(argument_count);
+}
+
+
 void FlowGraphCompiler::EmitStaticCall(const Function& function,
                                        const Array& arguments_descriptor,
                                        intptr_t argument_count,
                                        intptr_t deopt_id,
                                        intptr_t token_pos,
                                        LocationSummary* locs) {
   __ LoadObject(EDX, arguments_descriptor);
   // Do not use the code from the function, but let the code be patched so that
   // we can record the outgoing edges to other code.
   GenerateDartCall(deopt_id,
@@ skipping 320 matching lines @@
   __ popl(ECX);
   __ popl(EAX);
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32