[TypeFeedbackVector] Root feedback vectors at function literal site.

src/builtins/arm64/builtins-arm64.cc

 // Copyright 2013 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.
 
 #if V8_TARGET_ARCH_ARM64
 
 #include "src/arm64/frames-arm64.h"
 #include "src/codegen.h"
 #include "src/debug/debug.h"
 #include "src/deoptimizer.h"
@@ skipping 1332 matching lines @@
   //  -- x1 : target function (preserved for callee)
   // -----------------------------------
   // First lookup code, maybe we don't need to compile!
   Label gotta_call_runtime;
   Label try_shared;
   Label loop_top, loop_bottom;
 
   Register closure = x1;
   Register map = x13;
   Register index = x2;
+
+  // Do we have a valid feedback vector?
+  __ Ldr(index, FieldMemOperand(closure, JSFunction::kFeedbackVectorOffset));
+  __ Ldr(index, FieldMemOperand(index, Cell::kValueOffset));
+  __ JumpIfRoot(index, Heap::kUndefinedValueRootIndex, &gotta_call_runtime);
+
   __ Ldr(map, FieldMemOperand(closure, JSFunction::kSharedFunctionInfoOffset));
   __ Ldr(map,
          FieldMemOperand(map, SharedFunctionInfo::kOptimizedCodeMapOffset));
   __ Ldrsw(index, UntagSmiFieldMemOperand(map, FixedArray::kLengthOffset));
   __ Cmp(index, Operand(2));
-  __ B(lt, &gotta_call_runtime);
+  __ B(lt, &try_shared);
 
-  // Find literals.
   // x3  : native context
   // x2  : length / index
   // x13 : optimized code map
   // stack[0] : new target
   // stack[4] : closure
   Register native_context = x4;
   __ Ldr(native_context, NativeContextMemOperand());
 
   __ Bind(&loop_top);
   Register temp = x5;
   Register array_pointer = x6;
 
   // Does the native context match?
   __ Add(array_pointer, map, Operand(index, LSL, kPointerSizeLog2));
   __ Ldr(temp, FieldMemOperand(array_pointer,
                                SharedFunctionInfo::kOffsetToPreviousContext));
   __ Ldr(temp, FieldMemOperand(temp, WeakCell::kValueOffset));
   __ Cmp(temp, native_context);
   __ B(ne, &loop_bottom);
-  // Feedback vector available?
-  __ Ldr(temp, FieldMemOperand(array_pointer,
-                               SharedFunctionInfo::kOffsetToPreviousLiterals));
-  __ Ldr(temp, FieldMemOperand(temp, WeakCell::kValueOffset));
-  __ JumpIfSmi(temp, &gotta_call_runtime);
-
-  // Save the feedback vector in the closure.
-  __ Str(temp, FieldMemOperand(closure, JSFunction::kFeedbackVectorOffset));
-  __ RecordWriteField(closure, JSFunction::kFeedbackVectorOffset, temp, x7,
-                      kLRHasNotBeenSaved, kDontSaveFPRegs, EMIT_REMEMBERED_SET,
-                      OMIT_SMI_CHECK);
 
   // Code available?
   Register entry = x7;
   __ Ldr(entry,
          FieldMemOperand(array_pointer,
                          SharedFunctionInfo::kOffsetToPreviousCachedCode));
   __ Ldr(entry, FieldMemOperand(entry, WeakCell::kValueOffset));
   __ JumpIfSmi(entry, &try_shared);
 
-  // Found literals and code. Get them into the closure and return.
+  // Found code. Get it into the closure and return.
   __ Add(entry, entry, Operand(Code::kHeaderSize - kHeapObjectTag));
   __ Str(entry, FieldMemOperand(closure, JSFunction::kCodeEntryOffset));
   __ RecordWriteCodeEntryField(closure, entry, x5);
 
   // Link the closure into the optimized function list.
   // x7 : code entry
   // x4 : native context
   // x1 : closure
   __ Ldr(x8,
          ContextMemOperand(native_context, Context::OPTIMIZED_FUNCTIONS_LIST));
   __ Str(x8, FieldMemOperand(closure, JSFunction::kNextFunctionLinkOffset));
   __ RecordWriteField(closure, JSFunction::kNextFunctionLinkOffset, x8, x13,
                       kLRHasNotBeenSaved, kDontSaveFPRegs, EMIT_REMEMBERED_SET,
                       OMIT_SMI_CHECK);
   const int function_list_offset =
       Context::SlotOffset(Context::OPTIMIZED_FUNCTIONS_LIST);
   __ Str(closure,
          ContextMemOperand(native_context, Context::OPTIMIZED_FUNCTIONS_LIST));
   __ Mov(x5, closure);
   __ RecordWriteContextSlot(native_context, function_list_offset, x5, x13,
                             kLRHasNotBeenSaved, kDontSaveFPRegs);
   __ Jump(entry);
 
   __ Bind(&loop_bottom);
   __ Sub(index, index, Operand(SharedFunctionInfo::kEntryLength));
   __ Cmp(index, Operand(1));
   __ B(gt, &loop_top);
 
-  // We found neither literals nor code.
-  __ B(&gotta_call_runtime);
-
+  // We found no code.
   __ Bind(&try_shared);
   __ Ldr(entry,
          FieldMemOperand(closure, JSFunction::kSharedFunctionInfoOffset));
   // Is the shared function marked for tier up?
   __ Ldrb(temp, FieldMemOperand(
                     entry, SharedFunctionInfo::kMarkedForTierUpByteOffset));
   __ TestAndBranchIfAnySet(
       temp, 1 << SharedFunctionInfo::kMarkedForTierUpBitWithinByte,
       &gotta_call_runtime);
 
@@ skipping 1784 matching lines @@
     __ Unreachable();
   }
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM