[crankshaft] Support ES6 tail call elimination.

src/mips64/macro-assembler-mips64.cc

Index: src/mips64/macro-assembler-mips64.cc
diff --git a/src/mips64/macro-assembler-mips64.cc b/src/mips64/macro-assembler-mips64.cc
index b49fa76e064a803dc10b7fb81e7f96fde4a84cc4..831dbc5ac70cfd1daea291be24620e81c6a78127 100644
--- a/src/mips64/macro-assembler-mips64.cc
+++ b/src/mips64/macro-assembler-mips64.cc
@@ -4551,6 +4551,65 @@ void MacroAssembler::MovToFloatParameters(DoubleRegister src1,
 // -----------------------------------------------------------------------------
 // JavaScript invokes.
 
+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;
+  Dlsa(dst_reg, fp, caller_args_count_reg, kPointerSizeLog2);
+  Daddu(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()) {
+    Dlsa(src_reg, sp, callee_args_count.reg(), kPointerSizeLog2);
+    Daddu(src_reg, src_reg, Operand(kPointerSize));
+  } else {
+    Daddu(src_reg, sp,
+          Operand((callee_args_count.immediate() + 1) * kPointerSize));
+  }
+
+  if (FLAG_debug_code) {
+    Check(lo, kStackAccessBelowStackPointer, src_reg, Operand(dst_reg));
+  }
+
+  // Restore caller's frame pointer and return address now as they will be
+  // overwritten by the copying loop.
+  ld(ra, MemOperand(fp, StandardFrameConstants::kCallerPCOffset));
+  ld(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;
+  Branch(&entry);
+  bind(&loop);
+  Dsubu(src_reg, src_reg, Operand(kPointerSize));
+  Dsubu(dst_reg, dst_reg, Operand(kPointerSize));
+  ld(tmp_reg, MemOperand(src_reg));
+  sd(tmp_reg, MemOperand(dst_reg));
+  bind(&entry);
+  Branch(&loop, ne, sp, Operand(src_reg));
+
+  // Leave current frame.
+  mov(sp, dst_reg);
+}
+
 void MacroAssembler::InvokePrologue(const ParameterCount& expected,
                                     const ParameterCount& actual,
                                     Label* done,