KeyedLoadIC should have same register spec as LoadIC.

src/x64/ic-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/codegen.h"
 #include "src/ic-inl.h"
@@ skipping 309 matching lines @@
   __ testb(FieldOperand(map, Map::kInstanceTypeOffset),
            Immediate(kIsNotInternalizedMask));
   __ j(not_zero, not_unique);
 
   __ bind(&unique);
 }
 
 
 
 void KeyedLoadIC::GenerateGeneric(MacroAssembler* masm) {
-  // ----------- S t a t e -------------
-  //  -- rax    : key
-  //  -- rdx    : receiver
-  //  -- rsp[0] : return address
-  // -----------------------------------
-  ASSERT(rdx.is(ReceiverRegister()));
-  ASSERT(rax.is(NameRegister()));
+  // The return address is on the stack.
   Label slow, check_name, index_smi, index_name, property_array_property;
   Label probe_dictionary, check_number_dictionary;
 
+  Register receiver = ReceiverRegister();
+  Register key = NameRegister();
+  ASSERT(receiver.is(rdx));
+  ASSERT(key.is(rcx));
+
   // Check that the key is a smi.
-  __ JumpIfNotSmi(rax, &check_name);
+  __ JumpIfNotSmi(key, &check_name);
   __ bind(&index_smi);
   // Now the key is known to be a smi. This place is also jumped to from below
   // where a numeric string is converted to a smi.
 
   GenerateKeyedLoadReceiverCheck(
-      masm, rdx, rcx, Map::kHasIndexedInterceptor, &slow);
+      masm, receiver, rax, Map::kHasIndexedInterceptor, &slow);
 
   // Check the receiver's map to see if it has fast elements.
-  __ CheckFastElements(rcx, &check_number_dictionary);
+  __ CheckFastElements(rax, &check_number_dictionary);
 
   GenerateFastArrayLoad(masm,
-                        rdx,
+                        receiver,
+                        key,
                         rax,
-                        rcx,
                         rbx,
                         rax,
                         NULL,
                         &slow);
   Counters* counters = masm->isolate()->counters();
   __ IncrementCounter(counters->keyed_load_generic_smi(), 1);
   __ ret(0);
 
   __ bind(&check_number_dictionary);
-  __ SmiToInteger32(rbx, rax);
-  __ movp(rcx, FieldOperand(rdx, JSObject::kElementsOffset));
+  __ SmiToInteger32(rbx, key);
+  __ movp(rax, FieldOperand(receiver, JSObject::kElementsOffset));
 
   // Check whether the elements is a number dictionary.
-  // rdx: receiver
-  // rax: key
+  // receiver: receiver

[Jakob Kummerow, 2014/06/26 16:17:10]

Yay for high-entropy comments! :-P

AFAICS, the |receiver| register always contains the receiver, and the |key|
register always contains the key (it is only overwritten with the "new"  key in
case of heapnumber->smi conversion). So you could drop the comments about those
two.

[mvstanton, 2014/06/30 13:19:09]

Will do, thanks.

+  // key: key
   // rbx: key as untagged int32
-  // rcx: elements
-  __ CompareRoot(FieldOperand(rcx, HeapObject::kMapOffset),
+  // rax: elements
+  __ CompareRoot(FieldOperand(rax, HeapObject::kMapOffset),
                  Heap::kHashTableMapRootIndex);
   __ j(not_equal, &slow);
-  __ LoadFromNumberDictionary(&slow, rcx, rax, rbx, r9, rdi, rax);
+  __ LoadFromNumberDictionary(&slow, rax, key, rbx, r9, rdi, rax);
   __ ret(0);
 
   __ bind(&slow);
   // Slow case: Jump to runtime.
-  // rdx: receiver
-  // rax: key
+  // receiver: receiver
+  // key: key
   __ IncrementCounter(counters->keyed_load_generic_slow(), 1);
   GenerateRuntimeGetProperty(masm);
 
   __ bind(&check_name);
-  GenerateKeyNameCheck(masm, rax, rcx, rbx, &index_name, &slow);
+  GenerateKeyNameCheck(masm, key, rax, rbx, &index_name, &slow);
 
   GenerateKeyedLoadReceiverCheck(
-      masm, rdx, rcx, Map::kHasNamedInterceptor, &slow);
+      masm, receiver, rax, Map::kHasNamedInterceptor, &slow);
 
   // If the receiver is a fast-case object, check the keyed lookup
-  // cache. Otherwise probe the dictionary leaving result in rcx.
-  __ movp(rbx, FieldOperand(rdx, JSObject::kPropertiesOffset));
+  // cache. Otherwise probe the dictionary leaving result in key.
+  __ movp(rbx, FieldOperand(receiver, JSObject::kPropertiesOffset));
   __ CompareRoot(FieldOperand(rbx, HeapObject::kMapOffset),
                  Heap::kHashTableMapRootIndex);
   __ j(equal, &probe_dictionary);
 
   // Load the map of the receiver, compute the keyed lookup cache hash
   // based on 32 bits of the map pointer and the string hash.
-  __ movp(rbx, FieldOperand(rdx, HeapObject::kMapOffset));
-  __ movl(rcx, rbx);
-  __ shrl(rcx, Immediate(KeyedLookupCache::kMapHashShift));
-  __ movl(rdi, FieldOperand(rax, String::kHashFieldOffset));
+  __ movp(rbx, FieldOperand(receiver, HeapObject::kMapOffset));
+  __ movl(rax, rbx);
+  __ shrl(rax, Immediate(KeyedLookupCache::kMapHashShift));
+  __ movl(rdi, FieldOperand(key, String::kHashFieldOffset));
   __ shrl(rdi, Immediate(String::kHashShift));
-  __ xorp(rcx, rdi);
+  __ xorp(rax, rdi);
   int mask = (KeyedLookupCache::kCapacityMask & KeyedLookupCache::kHashMask);
-  __ andp(rcx, Immediate(mask));
+  __ andp(rax, Immediate(mask));
 
   // Load the key (consisting of map and internalized string) from the cache and
   // check for match.
   Label load_in_object_property;
   static const int kEntriesPerBucket = KeyedLookupCache::kEntriesPerBucket;
   Label hit_on_nth_entry[kEntriesPerBucket];
   ExternalReference cache_keys
       = ExternalReference::keyed_lookup_cache_keys(masm->isolate());
 
   for (int i = 0; i < kEntriesPerBucket - 1; i++) {
     Label try_next_entry;
-    __ movp(rdi, rcx);
+    __ movp(rdi, rax);
     __ shlp(rdi, Immediate(kPointerSizeLog2 + 1));
     __ LoadAddress(kScratchRegister, cache_keys);
     int off = kPointerSize * i * 2;
     __ cmpp(rbx, Operand(kScratchRegister, rdi, times_1, off));
     __ j(not_equal, &try_next_entry);
-    __ cmpp(rax, Operand(kScratchRegister, rdi, times_1, off + kPointerSize));
+    __ cmpp(key, Operand(kScratchRegister, rdi, times_1, off + kPointerSize));
     __ j(equal, &hit_on_nth_entry[i]);
     __ bind(&try_next_entry);
   }
 
   int off = kPointerSize * (kEntriesPerBucket - 1) * 2;
   __ cmpp(rbx, Operand(kScratchRegister, rdi, times_1, off));
   __ j(not_equal, &slow);
-  __ cmpp(rax, Operand(kScratchRegister, rdi, times_1, off + kPointerSize));
+  __ cmpp(key, Operand(kScratchRegister, rdi, times_1, off + kPointerSize));
   __ j(not_equal, &slow);
 
   // Get field offset, which is a 32-bit integer.
   ExternalReference cache_field_offsets
       = ExternalReference::keyed_lookup_cache_field_offsets(masm->isolate());
 
   // Hit on nth entry.
   for (int i = kEntriesPerBucket - 1; i >= 0; i--) {
     __ bind(&hit_on_nth_entry[i]);
     if (i != 0) {
-      __ addl(rcx, Immediate(i));
+      __ addl(rax, Immediate(i));
     }
     __ LoadAddress(kScratchRegister, cache_field_offsets);
-    __ movl(rdi, Operand(kScratchRegister, rcx, times_4, 0));
-    __ movzxbp(rcx, FieldOperand(rbx, Map::kInObjectPropertiesOffset));
-    __ subp(rdi, rcx);
+    __ movl(rdi, Operand(kScratchRegister, rax, times_4, 0));
+    __ movzxbp(rax, FieldOperand(rbx, Map::kInObjectPropertiesOffset));
+    __ subp(rdi, rax);
     __ j(above_equal, &property_array_property);
     if (i != 0) {
       __ jmp(&load_in_object_property);
     }
   }
 
   // Load in-object property.
   __ bind(&load_in_object_property);
-  __ movzxbp(rcx, FieldOperand(rbx, Map::kInstanceSizeOffset));
-  __ addp(rcx, rdi);
-  __ movp(rax, FieldOperand(rdx, rcx, times_pointer_size, 0));
+  __ movzxbp(rax, FieldOperand(rbx, Map::kInstanceSizeOffset));
+  __ addp(rax, rdi);
+  __ movp(rax, FieldOperand(receiver, rax, times_pointer_size, 0));
   __ IncrementCounter(counters->keyed_load_generic_lookup_cache(), 1);
   __ ret(0);
 
   // Load property array property.
   __ bind(&property_array_property);
-  __ movp(rax, FieldOperand(rdx, JSObject::kPropertiesOffset));
+  __ movp(rax, FieldOperand(receiver, JSObject::kPropertiesOffset));
   __ movp(rax, FieldOperand(rax, rdi, times_pointer_size,
                             FixedArray::kHeaderSize));
   __ IncrementCounter(counters->keyed_load_generic_lookup_cache(), 1);
   __ ret(0);
 
   // Do a quick inline probe of the receiver's dictionary, if it
   // exists.
   __ bind(&probe_dictionary);
-  // rdx: receiver
-  // rax: key
+  // receiver: receiver
+  // key: key
   // rbx: elements
 
-  __ movp(rcx, FieldOperand(rdx, JSObject::kMapOffset));
-  __ movb(rcx, FieldOperand(rcx, Map::kInstanceTypeOffset));
-  GenerateGlobalInstanceTypeCheck(masm, rcx, &slow);
+  __ movp(rax, FieldOperand(receiver, JSObject::kMapOffset));
+  __ movb(rax, FieldOperand(rax, Map::kInstanceTypeOffset));
+  GenerateGlobalInstanceTypeCheck(masm, rax, &slow);
 
-  GenerateDictionaryLoad(masm, &slow, rbx, rax, rcx, rdi, rax);
+  GenerateDictionaryLoad(masm, &slow, rbx, key, rax, rdi, rax);
   __ IncrementCounter(counters->keyed_load_generic_symbol(), 1);
   __ ret(0);
 
   __ bind(&index_name);
-  __ IndexFromHash(rbx, rax);
+  __ IndexFromHash(rbx, key);
   __ jmp(&index_smi);
 }
 
 
 void KeyedLoadIC::GenerateString(MacroAssembler* masm) {
   // Return address is on the stack.
   Label miss;
 
   Register receiver = ReceiverRegister();
   Register index = NameRegister();
-  Register scratch = rcx;
+  Register scratch = rbx;
   Register result = rax;
   ASSERT(!scratch.is(receiver) && !scratch.is(index));
 
   StringCharAtGenerator char_at_generator(receiver,
                                           index,
                                           scratch,
                                           result,
                                           &miss,  // When not a string.
                                           &miss,  // When not a number.
                                           &miss,  // When index out of range.
                                           STRING_INDEX_IS_ARRAY_INDEX);
   char_at_generator.GenerateFast(masm);
   __ ret(0);
 
   StubRuntimeCallHelper call_helper;
   char_at_generator.GenerateSlow(masm, call_helper);
 
   __ bind(&miss);
   GenerateMiss(masm);
 }
 
 
 void KeyedLoadIC::GenerateIndexedInterceptor(MacroAssembler* masm) {
   // Return address is on the stack.
   Label slow;
 
   Register receiver = ReceiverRegister();
   Register key = NameRegister();
-  Register scratch = rcx;
+  Register scratch = rax;
   ASSERT(!scratch.is(receiver) && !scratch.is(key));
 
   // Check that the receiver isn't a smi.
   __ JumpIfSmi(receiver, &slow);
 
   // Check that the key is an array index, that is Uint32.
   STATIC_ASSERT(kSmiValueSize <= 32);
   __ JumpUnlessNonNegativeSmi(key, &slow);
 
   // Get the map of the receiver.
@@ skipping 340 matching lines @@
   __ j(greater_equal, slow_case);
   __ SmiToInteger64(scratch, key);
   return FieldOperand(backing_store,
                       scratch,
                       times_pointer_size,
                       FixedArray::kHeaderSize);
 }
 
 
 void KeyedLoadIC::GenerateSloppyArguments(MacroAssembler* masm) {
-  // ----------- S t a t e -------------
-  //  -- rax    : key
-  //  -- rdx    : receiver
-  //  -- rsp[0] : return address
-  // -----------------------------------
-  ASSERT(rdx.is(ReceiverRegister()));
-  ASSERT(rax.is(NameRegister()));
+  // The return address is on the stack.
+  Register receiver = ReceiverRegister();
+  Register key = NameRegister();
+  ASSERT(receiver.is(rdx));
+  ASSERT(key.is(rcx));
+
   Label slow, notin;
   Operand mapped_location =
       GenerateMappedArgumentsLookup(
-          masm, rdx, rax, rbx, rcx, rdi, &notin, &slow);
+          masm, receiver, key, rbx, rax, rdi, &notin, &slow);
   __ movp(rax, mapped_location);
   __ Ret();
   __ bind(&notin);
   // The unmapped lookup expects that the parameter map is in rbx.
   Operand unmapped_location =
-      GenerateUnmappedArgumentsLookup(masm, rax, rbx, rcx, &slow);
+      GenerateUnmappedArgumentsLookup(masm, key, rbx, rax, &slow);
   __ CompareRoot(unmapped_location, Heap::kTheHoleValueRootIndex);
   __ j(equal, &slow);
   __ movp(rax, unmapped_location);
   __ Ret();
   __ bind(&slow);
   GenerateMiss(masm);
 }
 
 
 void KeyedStoreIC::GenerateSloppyArguments(MacroAssembler* masm) {
@@ skipping 30 matching lines @@
                  EMIT_REMEMBERED_SET,
                  INLINE_SMI_CHECK);
   __ Ret();
   __ bind(&slow);
   GenerateMiss(masm);
 }
 
 
 void LoadIC::GenerateMegamorphic(MacroAssembler* masm) {
   // ----------- S t a t e -------------
-  //  -- rax    : receiver
+  //  -- rdx    : receiver
   //  -- rcx    : name
   //  -- rsp[0] : return address
   // -----------------------------------
-  ASSERT(rax.is(ReceiverRegister()));
+  ASSERT(rdx.is(ReceiverRegister()));
   ASSERT(rcx.is(NameRegister()));
 
   // Probe the stub cache.
   Code::Flags flags = Code::ComputeHandlerFlags(Code::LOAD_IC);
   masm->isolate()->stub_cache()->GenerateProbe(
-      masm, flags, rax, rcx, rbx, rdx);
+      masm, flags, rdx, rcx, rbx, rax);
 
   GenerateMiss(masm);
 }
 
 
 void LoadIC::GenerateNormal(MacroAssembler* masm) {
   // ----------- S t a t e -------------
-  //  -- rax    : receiver
+  //  -- rdx    : receiver
   //  -- rcx    : name
   //  -- rsp[0] : return address
   // -----------------------------------
-  ASSERT(rax.is(ReceiverRegister()));
+  ASSERT(rdx.is(ReceiverRegister()));
   ASSERT(rcx.is(NameRegister()));
   Label miss, slow;
 
-  GenerateNameDictionaryReceiverCheck(masm, rax, rdx, rbx, &miss);
+  GenerateNameDictionaryReceiverCheck(masm, rdx, rax, rbx, &miss);
 
-  //  rdx: elements
+  //  rax: elements
   // Search the dictionary placing the result in rax.
-  GenerateDictionaryLoad(masm, &slow, rdx, rcx, rbx, rdi, rax);
+  GenerateDictionaryLoad(masm, &slow, rax, rcx, rbx, rdi, rax);
   __ ret(0);
 
   // Dictionary load failed, go slow (but don't miss).
   __ bind(&slow);
   GenerateRuntimeGetProperty(masm);
 
   // Cache miss: Jump to runtime.
   __ bind(&miss);
   GenerateMiss(masm);
 }
@@ skipping 50 matching lines @@
   __ PushReturnAddressFrom(KeyedLoadIC_TempRegister());
 
   // Perform tail call to the entry.
   ExternalReference ref =
       ExternalReference(IC_Utility(kKeyedLoadIC_Miss), masm->isolate());
   __ TailCallExternalReference(ref, 2, 1);
 }
 
 
 // IC register specifications
-const Register LoadIC::ReceiverRegister() { return rax; }
+const Register LoadIC::ReceiverRegister() { return rdx; }
 const Register LoadIC::NameRegister() { return rcx; }
-const Register KeyedLoadIC::ReceiverRegister() { return rdx; }
-const Register KeyedLoadIC::NameRegister() { return rax; }
 
 
 void KeyedLoadIC::GenerateRuntimeGetProperty(MacroAssembler* masm) {
   // The return address is on the stack.
 
   __ PopReturnAddressTo(KeyedLoadIC_TempRegister());
   __ Push(ReceiverRegister());  // receiver
   __ Push(NameRegister());  // name
   __ PushReturnAddressFrom(KeyedLoadIC_TempRegister());
 
@@ skipping 235 matching lines @@
   Condition cc = (check == ENABLE_INLINED_SMI_CHECK)
       ? (*jmp_address == Assembler::kJncShortOpcode ? not_zero : zero)
       : (*jmp_address == Assembler::kJnzShortOpcode ? not_carry : carry);
   *jmp_address = static_cast<byte>(Assembler::kJccShortPrefix | cc);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64