X87: [crankshaft] Support ES6 tail call elimination.

src/x87/macro-assembler-x87.cc

Index: src/x87/macro-assembler-x87.cc
diff --git a/src/x87/macro-assembler-x87.cc b/src/x87/macro-assembler-x87.cc
index 0c459ebfd420f5208d8b4b7c05ef6a26d831a4c3..b5b09cf1c3b9dfd15d8058872636e85abd75ac0a 100644
--- a/src/x87/macro-assembler-x87.cc
+++ b/src/x87/macro-assembler-x87.cc
@@ -2024,6 +2024,77 @@ void MacroAssembler::JumpToExternalReference(const ExternalReference& ext) {
   jmp(ces.GetCode(), RelocInfo::CODE_TARGET);
 }
 
+void MacroAssembler::PrepareForTailCall(const ParameterCount& callee_args_count,
+                                        Register caller_args_count_reg,
+                                        Register scratch0, Register scratch1,
+                                        ReturnAddressState ra_state) {
+#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 destination address where we will put the return address
+  // after we drop current frame.
+  Register new_sp_reg = scratch0;
+  if (callee_args_count.is_reg()) {
+    sub(caller_args_count_reg, callee_args_count.reg());
+    lea(new_sp_reg, Operand(ebp, caller_args_count_reg, times_pointer_size,
+                            StandardFrameConstants::kCallerPCOffset));
+  } else {
+    lea(new_sp_reg, Operand(ebp, caller_args_count_reg, times_pointer_size,
+                            StandardFrameConstants::kCallerPCOffset -
+                                callee_args_count.immediate() * kPointerSize));
+  }
+
+  if (FLAG_debug_code) {
+    cmp(esp, new_sp_reg);
+    Check(below, kStackAccessBelowStackPointer);
+  }
+
+  // Copy return address from caller's frame to current frame's return address
+  // to avoid its trashing and let the following loop copy it to the right
+  // place.
+  Register tmp_reg = scratch1;
+  if (ra_state == ReturnAddressState::kOnStack) {
+    mov(tmp_reg, Operand(ebp, StandardFrameConstants::kCallerPCOffset));
+    mov(Operand(esp, 0), tmp_reg);
+  } else {
+    DCHECK(ReturnAddressState::kNotOnStack == ra_state);
+    Push(Operand(ebp, StandardFrameConstants::kCallerPCOffset));
+  }
+
+  // Restore caller's frame pointer now as it could be overwritten by
+  // the copying loop.
+  mov(ebp, Operand(ebp, StandardFrameConstants::kCallerFPOffset));
+
+  // +2 here is to copy both receiver and return address.
+  Register count_reg = caller_args_count_reg;
+  if (callee_args_count.is_reg()) {
+    lea(count_reg, Operand(callee_args_count.reg(), 2));
+  } else {
+    mov(count_reg, Immediate(callee_args_count.immediate() + 2));
+    // TODO(ishell): Unroll copying loop for small immediate values.
+  }
+
+  // Now copy callee arguments to the caller frame going backwards to avoid
+  // callee arguments corruption (source and destination areas could overlap).
+  Label loop, entry;
+  jmp(&entry, Label::kNear);
+  bind(&loop);
+  dec(count_reg);
+  mov(tmp_reg, Operand(esp, count_reg, times_pointer_size, 0));
+  mov(Operand(new_sp_reg, count_reg, times_pointer_size, 0), tmp_reg);
+  bind(&entry);
+  cmp(count_reg, Immediate(0));
+  j(not_equal, &loop, Label::kNear);
+
+  // Leave current frame.
+  mov(esp, new_sp_reg);
+}
 
 void MacroAssembler::InvokePrologue(const ParameterCount& expected,
                                     const ParameterCount& actual,