Detect simple tail calls

src/compiler/arm64/code-generator-arm64.cc

Index: src/compiler/arm64/code-generator-arm64.cc
diff --git a/src/compiler/arm64/code-generator-arm64.cc b/src/compiler/arm64/code-generator-arm64.cc
index 51106c2a3c9f80b5408bfa304e6b66fc516825e3..dc045af64b4775f6765e1f13644ecf8167e8da8c 100644
--- a/src/compiler/arm64/code-generator-arm64.cc
+++ b/src/compiler/arm64/code-generator-arm64.cc
@@ -343,6 +343,20 @@ Condition FlagsConditionToCondition(FlagsCondition condition) {
   } while (0)
 
 
+void CodeGenerator::AssembleDeconstructActivationRecord() {
+  CallDescriptor* descriptor = linkage()->GetIncomingDescriptor();
+  int stack_slots = frame()->GetSpillSlotCount();
+  if (descriptor->IsJSFunctionCall() || stack_slots > 0) {
+    __ Mov(jssp, fp);
+    __ Pop(fp, lr);
+    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) {
   Arm64OperandConverter i(this, instr);
@@ -361,6 +375,18 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       RecordCallPosition(instr);
       break;
     }
+    case kArchTailCallCodeObject: {
+      AssembleDeconstructActivationRecord();
+      if (instr->InputAt(0)->IsImmediate()) {
+        __ Jump(Handle<Code>::cast(i.InputHeapObject(0)),
+                RelocInfo::CODE_TARGET);
+      } else {
+        Register target = i.InputRegister(0);
+        __ Add(target, target, Code::kHeaderSize - kHeapObjectTag);
+        __ Jump(target);
+      }
+      break;
+    }
     case kArchCallJSFunction: {
       EnsureSpaceForLazyDeopt();
       Register func = i.InputRegister(0);
@@ -377,6 +403,21 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       RecordCallPosition(instr);
       break;
     }
+    case kArchTailCallJSFunction: {
+      Register func = i.InputRegister(0);
+      if (FLAG_debug_code) {
+        // Check the function's context matches the context argument.
+        UseScratchRegisterScope scope(masm());
+        Register temp = scope.AcquireX();
+        __ Ldr(temp, FieldMemOperand(func, JSFunction::kContextOffset));
+        __ cmp(cp, temp);
+        __ Assert(eq, kWrongFunctionContext);
+      }
+      AssembleDeconstructActivationRecord();
+      __ Ldr(x10, FieldMemOperand(func, JSFunction::kCodeEntryOffset));
+      __ Jump(x10);
+      break;
+    }
     case kArchJmp:
       AssembleArchJump(i.InputRpo(0));
       break;