[crankshaft] Support ES6 tail call elimination.

src/mips/macro-assembler-mips.cc

 
 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <limits.h>  // For LONG_MIN, LONG_MAX.
 
 #if V8_TARGET_ARCH_MIPS
 
 #include "src/base/bits.h"
@@ skipping 4077 matching lines @@
       Move(a1, a0, src1);
       Move(a3, a2, src2);
     }
   }
 }
 
 
 // -----------------------------------------------------------------------------
 // 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,
                                     bool* definitely_mismatches,
                                     InvokeFlag flag,
                                     const CallWrapper& call_wrapper) {
   bool definitely_matches = false;
   *definitely_mismatches = false;
   Label regular_invoke;
 
@@ skipping 1805 matching lines @@
   if (mag.shift > 0) sra(result, result, mag.shift);
   srl(at, dividend, 31);
   Addu(result, result, Operand(at));
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS