Detect simple tail calls

src/compiler/mips/code-generator-mips.cc

 // Copyright 2014 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 "src/compiler/code-generator.h"
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
 #include "src/mips/macro-assembler-mips.h"
 #include "src/scopes.h"
@@ skipping 376 matching lines @@
     __ asm_instr(i.OutputDoubleRegister(), i.InputDoubleRegister(0));          \
     __ Move(at, kScratchReg2, i.OutputDoubleRegister());                       \
     __ or_(at, at, kScratchReg2);                                              \
     __ Branch(USE_DELAY_SLOT, ool->entry(), eq, at, Operand(zero_reg));        \
     __ cvt_d_l(i.OutputDoubleRegister(), i.OutputDoubleRegister());            \
     __ bind(ool->exit());                                                      \
     __ bind(&done);                                                            \
   } while (0)
 
 
+void CodeGenerator::AssembleDeconstructActivationRecord() {
+  CallDescriptor* descriptor = linkage()->GetIncomingDescriptor();
+  int stack_slots = frame()->GetSpillSlotCount();
+  if (descriptor->IsJSFunctionCall() || stack_slots > 0) {
+    __ mov(sp, fp);
+    __ Pop(ra, fp);
+    int pop_count = descriptor->IsJSFunctionCall()
+                        ? static_cast<int>(descriptor->JSParameterCount())
+                        : 0;
+    __ Drop(pop_count);
+  }
+}
+
+
 // Assembles an instruction after register allocation, producing machine code.
 void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
   MipsOperandConverter i(this, instr);
   InstructionCode opcode = instr->opcode();
 
   switch (ArchOpcodeField::decode(opcode)) {
     case kArchCallCodeObject: {
       EnsureSpaceForLazyDeopt();
       if (instr->InputAt(0)->IsImmediate()) {
         __ Call(Handle<Code>::cast(i.InputHeapObject(0)),
                 RelocInfo::CODE_TARGET);
       } else {
         __ addiu(at, i.InputRegister(0), Code::kHeaderSize - kHeapObjectTag);
         __ Call(at);
       }
       RecordCallPosition(instr);
       break;
     }
+    case kArchTailCallCodeObject: {
+      AssembleDeconstructActivationRecord();
+      if (instr->InputAt(0)->IsImmediate()) {
+        __ Jump(Handle<Code>::cast(i.InputHeapObject(0)),
+                RelocInfo::CODE_TARGET);
+      } else {
+        __ addiu(at, i.InputRegister(0), Code::kHeaderSize - kHeapObjectTag);
+        __ Jump(at);
+      }
+      break;
+    }
     case kArchCallJSFunction: {
       EnsureSpaceForLazyDeopt();
       Register func = i.InputRegister(0);
       if (FLAG_debug_code) {
         // Check the function's context matches the context argument.
         __ lw(kScratchReg, FieldMemOperand(func, JSFunction::kContextOffset));
         __ Assert(eq, kWrongFunctionContext, cp, Operand(kScratchReg));
       }
 
       __ lw(at, FieldMemOperand(func, JSFunction::kCodeEntryOffset));
       __ Call(at);
       RecordCallPosition(instr);
       break;
     }
+    case kArchTailCallJSFunction: {
+      Register func = i.InputRegister(0);
+      if (FLAG_debug_code) {
+        // Check the function's context matches the context argument.
+        __ lw(kScratchReg, FieldMemOperand(func, JSFunction::kContextOffset));
+        __ Assert(eq, kWrongFunctionContext, cp, Operand(kScratchReg));
+      }
+
+      AssembleDeconstructActivationRecord();
+      __ lw(at, FieldMemOperand(func, JSFunction::kCodeEntryOffset));
+      __ Jump(at);
+      break;
+    }
     case kArchJmp:
       AssembleArchJump(i.InputRpo(0));
       break;
     case kArchLookupSwitch:
       AssembleArchLookupSwitch(instr);
       break;
     case kArchTableSwitch:
       AssembleArchTableSwitch(instr);
       break;
     case kArchNop:
@@ skipping 860 matching lines @@
     }
   }
   MarkLazyDeoptSite();
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8