[turbofan] Support variable size argument popping in TF-generated functions

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 f543b186823668e6e40b5ed8b3aa37b0e4a3df6b..1921f51a625c9297abb47bac3fad63ecc00b2dde 100644
--- a/src/compiler/arm64/code-generator-arm64.cc
+++ b/src/compiler/arm64/code-generator-arm64.cc
@@ -786,7 +786,7 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
       break;
     }
     case kArchRet:
-      AssembleReturn();
+      AssembleReturn(instr->InputAt(0));
       break;
     case kArchStackPointer:
       __ mov(i.OutputRegister(), masm()->StackPointer());
@@ -1857,8 +1857,7 @@ void CodeGenerator::AssembleConstructFrame() {
   }
 }
 
-
-void CodeGenerator::AssembleReturn() {
+void CodeGenerator::AssembleReturn(InstructionOperand* pop) {
   CallDescriptor* descriptor = linkage()->GetIncomingDescriptor();
 
   // Restore registers.
@@ -1895,6 +1894,14 @@ void CodeGenerator::AssembleReturn() {
   } else if (descriptor->UseNativeStack()) {
     pop_count += (pop_count & 1);  // align
   }
+
+  Arm64OperandConverter g(this, nullptr);
+  if (pop->IsImmediate()) {
+    DCHECK_EQ(Constant::kInt32, g.ToConstant(pop).type());
+    pop_count += g.ToConstant(pop).ToInt32();
+  } else {
+    __ Drop(g.ToRegister(pop));
+  }
   __ Drop(pop_count);
 
   if (descriptor->UseNativeStack()) {