[crankshaft] Support ES6 tail call elimination.

src/mips/macro-assembler-mips.cc

Index: src/mips/macro-assembler-mips.cc
diff --git a/src/mips/macro-assembler-mips.cc b/src/mips/macro-assembler-mips.cc
index 76b724ceebc6e41257ea0bd8e0fac541acc430d9..dd9e7d980e87438b7ff4d8b1d01745310aedc692 100644
--- a/src/mips/macro-assembler-mips.cc
+++ b/src/mips/macro-assembler-mips.cc
@@ -4095,6 +4095,65 @@ 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;
+  Lsa(dst_reg, fp, caller_args_count_reg, kPointerSizeLog2);
+  Addu(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()) {
+    Lsa(src_reg, sp, callee_args_count.reg(), kPointerSizeLog2);
+    Addu(src_reg, src_reg, Operand(kPointerSize));
+  } else {
+    Addu(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.
+  lw(ra, MemOperand(fp, StandardFrameConstants::kCallerPCOffset));
+  lw(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);
+  Subu(src_reg, src_reg, Operand(kPointerSize));
+  Subu(dst_reg, dst_reg, Operand(kPointerSize));
+  lw(tmp_reg, MemOperand(src_reg));
+  sw(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,