[crankshaft] Support ES6 tail call elimination.

src/arm64/macro-assembler-arm64.cc

Index: src/arm64/macro-assembler-arm64.cc
diff --git a/src/arm64/macro-assembler-arm64.cc b/src/arm64/macro-assembler-arm64.cc
index 953c3fd7f2bf245e24fbe1ed9e0850d726bf9d07..c4a3a998506ccfebb46a1dc8ce08fb4dcbb0c088 100644
--- a/src/arm64/macro-assembler-arm64.cc
+++ b/src/arm64/macro-assembler-arm64.cc
@@ -2330,6 +2330,66 @@ void MacroAssembler::JumpIfNotUniqueNameInstanceType(Register type,
   B(ne, not_unique_name);
 }
 
+void MacroAssembler::PrepareForTailCall(const ParameterCount& callee_args_count,
+                                        Register caller_args_count_reg,
+                                        Register scratch0, Register scratch1) {
+#if DEBUG
+  if (callee_args_count.is_reg()) {
+    DCHECK(!AreAliased(callee_args_count.reg(), caller_args_count_reg, scratch0,
+                       scratch1));
+  } else {
+    DCHECK(!AreAliased(caller_args_count_reg, scratch0, scratch1));
+  }
+#endif
+
+  // 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 = scratch0;
+  __ add(dst_reg, fp, Operand(caller_args_count_reg, LSL, kPointerSizeLog2));
+  __ add(dst_reg, dst_reg,
+         Operand(StandardFrameConstants::kCallerSPOffset + kPointerSize));
+
+  Register src_reg = caller_args_count_reg;
+  // Calculate the end of source area. +kPointerSize is for the receiver.
+  if (callee_args_count.is_reg()) {
+    add(src_reg, jssp, Operand(callee_args_count.reg(), LSL, kPointerSizeLog2));
+    add(src_reg, src_reg, Operand(kPointerSize));
+  } else {
+    add(src_reg, jssp,
+        Operand((callee_args_count.immediate() + 1) * 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 = scratch1;
+  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();
+}
 
 void MacroAssembler::InvokePrologue(const ParameterCount& expected,
                                     const ParameterCount& actual,