[crankshaft] Support ES6 tail call elimination.

src/arm64/builtins-arm64.cc

Index: src/arm64/builtins-arm64.cc
diff --git a/src/arm64/builtins-arm64.cc b/src/arm64/builtins-arm64.cc
index 11f66a4ef46caa9f2607a40e693c082b14810c8d..281203818904e51084b0df6c8e193dc36a6c9986 100644
--- a/src/arm64/builtins-arm64.cc
+++ b/src/arm64/builtins-arm64.cc
@@ -1992,6 +1992,7 @@ void PrepareForTailCall(MacroAssembler* masm, Register args_reg,
   }
 
   // Check if next frame is an arguments adaptor frame.
+  Register caller_args_count_reg = scratch1;
   Label no_arguments_adaptor, formal_parameter_count_loaded;
   __ Ldr(scratch2, MemOperand(fp, StandardFrameConstants::kCallerFPOffset));
   __ Ldr(scratch3,
@@ -1999,11 +2000,11 @@ void PrepareForTailCall(MacroAssembler* masm, Register args_reg,
   __ Cmp(scratch3, Operand(Smi::FromInt(StackFrame::ARGUMENTS_ADAPTOR)));
   __ B(ne, &no_arguments_adaptor);
 
-  // Drop arguments adaptor frame and load arguments count.
+  // Drop current frame and load arguments count from arguments adaptor frame.
   __ mov(fp, scratch2);
-  __ Ldr(scratch1,
+  __ Ldr(caller_args_count_reg,
          MemOperand(fp, ArgumentsAdaptorFrameConstants::kLengthOffset));
-  __ SmiUntag(scratch1);
+  __ SmiUntag(caller_args_count_reg);
   __ B(&formal_parameter_count_loaded);
 
   __ bind(&no_arguments_adaptor);
@@ -2011,54 +2012,14 @@ void PrepareForTailCall(MacroAssembler* masm, Register args_reg,
   __ Ldr(scratch1, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
   __ Ldr(scratch1,
          FieldMemOperand(scratch1, JSFunction::kSharedFunctionInfoOffset));
-  __ Ldrsw(scratch1,
+  __ Ldrsw(caller_args_count_reg,
            FieldMemOperand(scratch1,
                            SharedFunctionInfo::kFormalParameterCountOffset));
   __ bind(&formal_parameter_count_loaded);
 
-  // Calculate the end of destination area where we will put the arguments
-  // after we drop current frame. We add kPointerSize to count the receiver
-  // argument which is not included into formal parameters count.
-  Register dst_reg = scratch2;
-  __ add(dst_reg, fp, Operand(scratch1, LSL, kPointerSizeLog2));
-  __ add(dst_reg, dst_reg,
-         Operand(StandardFrameConstants::kCallerSPOffset + kPointerSize));
-
-  Register src_reg = scratch1;
-  __ add(src_reg, jssp, Operand(args_reg, LSL, kPointerSizeLog2));
-  // Count receiver argument as well (not included in args_reg).
-  __ add(src_reg, src_reg, Operand(kPointerSize));
-
-  if (FLAG_debug_code) {
-    __ Cmp(src_reg, dst_reg);
-    __ Check(lo, kStackAccessBelowStackPointer);
-  }
-
-  // Restore caller's frame pointer and return address now as they will be
-  // overwritten by the copying loop.
-  __ Ldr(lr, MemOperand(fp, StandardFrameConstants::kCallerPCOffset));
-  __ Ldr(fp, MemOperand(fp, StandardFrameConstants::kCallerFPOffset));
-
-  // Now copy callee arguments to the caller frame going backwards to avoid
-  // callee arguments corruption (source and destination areas could overlap).
-
-  // Both src_reg and dst_reg are pointing to the word after the one to copy,
-  // so they must be pre-decremented in the loop.
-  Register tmp_reg = scratch3;
-  Label loop, entry;
-  __ B(&entry);
-  __ bind(&loop);
-  __ Ldr(tmp_reg, MemOperand(src_reg, -kPointerSize, PreIndex));
-  __ Str(tmp_reg, MemOperand(dst_reg, -kPointerSize, PreIndex));
-  __ bind(&entry);
-  __ Cmp(jssp, src_reg);
-  __ B(ne, &loop);
-
-  // Leave current frame.
-  __ Mov(jssp, dst_reg);
-  __ SetStackPointer(jssp);
-  __ AssertStackConsistency();
-
+  ParameterCount callee_args_count(args_reg);
+  __ PrepareForTailCall(callee_args_count, caller_args_count_reg, scratch2,
+                        scratch3);
   __ bind(&done);
 }
 }  // namespace