[crankshaft] Support ES6 tail call elimination.

src/crankshaft/mips/lithium-codegen-mips.cc

Index: src/crankshaft/mips/lithium-codegen-mips.cc
diff --git a/src/crankshaft/mips/lithium-codegen-mips.cc b/src/crankshaft/mips/lithium-codegen-mips.cc
index dd908dea5ca3c9c15ee965c831148091bc1bfcfc..38d3eaff340194935e121df2e7ac0cdd78a8b2e0 100644
--- a/src/crankshaft/mips/lithium-codegen-mips.cc
+++ b/src/crankshaft/mips/lithium-codegen-mips.cc
@@ -3130,15 +3130,24 @@ void LCodeGen::DoApplyArguments(LApplyArguments* instr) {
   __ sll(scratch, length, 2);
 
   __ bind(&invoke);
+
+  InvokeFlag flag = CALL_FUNCTION;
+  if (instr->hydrogen()->tail_call_mode() == TailCallMode::kAllow) {
+    // TODO(ishell): drop current frame before pushing arguments to the stack.
+    flag = JUMP_FUNCTION;
+    ParameterCount actual(a0);
+    // It is safe to use t0, t1 and t2 as scratch registers here given that
+    // we are not going to return to caller function anyway.
+    PrepareForTailCall(actual, t0, t1, t2);
+  }
+
   DCHECK(instr->HasPointerMap());
   LPointerMap* pointers = instr->pointer_map();
-  SafepointGenerator safepoint_generator(
-      this, pointers, Safepoint::kLazyDeopt);
+  SafepointGenerator safepoint_generator(this, pointers, Safepoint::kLazyDeopt);
   // The number of arguments is stored in receiver which is a0, as expected
   // by InvokeFunction.
   ParameterCount actual(receiver);
-  __ InvokeFunction(function, no_reg, actual, CALL_FUNCTION,
-                    safepoint_generator);
+  __ InvokeFunction(function, no_reg, actual, flag, safepoint_generator);
 }
 
 
@@ -3184,10 +3193,9 @@ void LCodeGen::DoDeclareGlobals(LDeclareGlobals* instr) {
   CallRuntime(Runtime::kDeclareGlobals, instr);
 }
 
-
 void LCodeGen::CallKnownFunction(Handle<JSFunction> function,
                                  int formal_parameter_count, int arity,
-                                 LInstruction* instr) {
+                                 bool is_tail_call, LInstruction* instr) {
   bool dont_adapt_arguments =
       formal_parameter_count == SharedFunctionInfo::kDontAdaptArgumentsSentinel;
   bool can_invoke_directly =
@@ -3204,17 +3212,35 @@ void LCodeGen::CallKnownFunction(Handle<JSFunction> function,
     __ LoadRoot(a3, Heap::kUndefinedValueRootIndex);
     __ li(a0, Operand(arity));
 
+    bool is_self_call = function.is_identical_to(info()->closure());
+
     // Invoke function.
-    __ lw(at, FieldMemOperand(function_reg, JSFunction::kCodeEntryOffset));
-    __ Call(at);
+    if (is_self_call) {
+      Handle<Code> self(reinterpret_cast<Code**>(__ CodeObject().location()));
+      if (is_tail_call) {
+        __ Jump(self, RelocInfo::CODE_TARGET);
+      } else {
+        __ Call(self, RelocInfo::CODE_TARGET);
+      }
+    } else {
+      __ lw(at, FieldMemOperand(function_reg, JSFunction::kCodeEntryOffset));
+      if (is_tail_call) {
+        __ Jump(at);
+      } else {
+        __ Call(at);
+      }
+    }
 
-    // Set up deoptimization.
-    RecordSafepointWithLazyDeopt(instr, RECORD_SIMPLE_SAFEPOINT);
+    if (!is_tail_call) {
+      // Set up deoptimization.
+      RecordSafepointWithLazyDeopt(instr, RECORD_SIMPLE_SAFEPOINT);
+    }
   } else {
     SafepointGenerator generator(this, pointers, Safepoint::kLazyDeopt);
-    ParameterCount count(arity);
+    ParameterCount actual(arity);
     ParameterCount expected(formal_parameter_count);
-    __ InvokeFunction(function_reg, expected, count, CALL_FUNCTION, generator);
+    InvokeFlag flag = is_tail_call ? JUMP_FUNCTION : CALL_FUNCTION;
+    __ InvokeFunction(function_reg, expected, actual, flag, generator);
   }
 }
 
@@ -3548,22 +3574,77 @@ void LCodeGen::DoMathClz32(LMathClz32* instr) {
   __ Clz(result, input);
 }
 
+void LCodeGen::PrepareForTailCall(const ParameterCount& actual,
+                                  Register scratch1, Register scratch2,
+                                  Register scratch3) {
+#if DEBUG
+  if (actual.is_reg()) {
+    DCHECK(!AreAliased(actual.reg(), scratch1, scratch2, scratch3));
+  } else {
+    DCHECK(!AreAliased(scratch1, scratch2, scratch3));
+  }
+#endif
+  if (FLAG_code_comments) {
+    if (actual.is_reg()) {
+      Comment(";;; PrepareForTailCall, actual: %s {", actual.reg().ToString());
+    } else {
+      Comment(";;; PrepareForTailCall, actual: %d {", actual.immediate());
+    }
+  }
+
+  // Check if next frame is an arguments adaptor frame.
+  Register caller_args_count_reg = scratch1;
+  Label no_arguments_adaptor, formal_parameter_count_loaded;
+  __ lw(scratch2, MemOperand(fp, StandardFrameConstants::kCallerFPOffset));
+  __ lw(scratch3, MemOperand(scratch2, StandardFrameConstants::kContextOffset));
+  __ Branch(&no_arguments_adaptor, ne, scratch3,
+            Operand(Smi::FromInt(StackFrame::ARGUMENTS_ADAPTOR)));
+
+  // Drop current frame and load arguments count from arguments adaptor frame.
+  __ mov(fp, scratch2);
+  __ lw(caller_args_count_reg,
+        MemOperand(fp, ArgumentsAdaptorFrameConstants::kLengthOffset));
+  __ SmiUntag(caller_args_count_reg);
+  __ Branch(&formal_parameter_count_loaded);
+
+  __ bind(&no_arguments_adaptor);
+  // Load caller's formal parameter count
+  __ lw(scratch1, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
+  __ lw(scratch1,
+        FieldMemOperand(scratch1, JSFunction::kSharedFunctionInfoOffset));
+  __ li(caller_args_count_reg, Operand(info()->literal()->parameter_count()));
+
+  __ bind(&formal_parameter_count_loaded);
+  __ PrepareForTailCall(actual, caller_args_count_reg, scratch2, scratch3);
+
+  Comment(";;; }");
+}
 
 void LCodeGen::DoInvokeFunction(LInvokeFunction* instr) {
+  HInvokeFunction* hinstr = instr->hydrogen();
   DCHECK(ToRegister(instr->context()).is(cp));
   DCHECK(ToRegister(instr->function()).is(a1));
   DCHECK(instr->HasPointerMap());
 
-  Handle<JSFunction> known_function = instr->hydrogen()->known_function();
+  bool is_tail_call = hinstr->tail_call_mode() == TailCallMode::kAllow;
+
+  if (is_tail_call) {
+    ParameterCount actual(instr->arity());
+    // It is safe to use t0, t1 and t2 as scratch registers here given that
+    // we are not going to return to caller function anyway.
+    PrepareForTailCall(actual, t0, t1, t2);
+  }
+
+  Handle<JSFunction> known_function = hinstr->known_function();
   if (known_function.is_null()) {
     LPointerMap* pointers = instr->pointer_map();
     SafepointGenerator generator(this, pointers, Safepoint::kLazyDeopt);
-    ParameterCount count(instr->arity());
-    __ InvokeFunction(a1, no_reg, count, CALL_FUNCTION, generator);
+    ParameterCount actual(instr->arity());
+    InvokeFlag flag = is_tail_call ? JUMP_FUNCTION : CALL_FUNCTION;
+    __ InvokeFunction(a1, no_reg, actual, flag, generator);
   } else {
-    CallKnownFunction(known_function,
-                      instr->hydrogen()->formal_parameter_count(),
-                      instr->arity(), instr);
+    CallKnownFunction(known_function, hinstr->formal_parameter_count(),
+                      instr->arity(), is_tail_call, instr);
   }
 }