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

src/compiler/ia32/code-generator-ia32.cc

Index: src/compiler/ia32/code-generator-ia32.cc
diff --git a/src/compiler/ia32/code-generator-ia32.cc b/src/compiler/ia32/code-generator-ia32.cc
index cca42fa2fd6d6a82b65d89819f3f0e17538151b5..3ec0479a9c9bdb082594977073cce9a0f829dec5 100644
--- a/src/compiler/ia32/code-generator-ia32.cc
+++ b/src/compiler/ia32/code-generator-ia32.cc
@@ -652,7 +652,7 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
       break;
     }
     case kArchRet:
-      AssembleReturn();
+      AssembleReturn(instr->InputAt(0));
       break;
     case kArchStackPointer:
       __ mov(i.OutputRegister(), esp);
@@ -1984,8 +1984,7 @@ void CodeGenerator::AssembleConstructFrame() {
   }
 }
 
-
-void CodeGenerator::AssembleReturn() {
+void CodeGenerator::AssembleReturn(InstructionOperand* pop) {
   CallDescriptor* descriptor = linkage()->GetIncomingDescriptor();
 
   const RegList saves = descriptor->CalleeSavedRegisters();
@@ -2009,10 +2008,21 @@ void CodeGenerator::AssembleReturn() {
       AssembleDeconstructFrame();
     }
   }
-  size_t pop_size = descriptor->StackParameterCount() * kPointerSize;
-  // Might need ecx for scratch if pop_size is too big.
+  // Might need ecx for scratch if pop_size is too big or if there is a variable
+  // pop count.
   DCHECK_EQ(0u, descriptor->CalleeSavedRegisters() & ecx.bit());
-  __ Ret(static_cast<int>(pop_size), ecx);
+  size_t pop_size = descriptor->StackParameterCount() * kPointerSize;
+  IA32OperandConverter g(this, nullptr);
+  if (pop->IsImmediate()) {
+    DCHECK_EQ(Constant::kInt32, g.ToConstant(pop).type());
+    pop_size += g.ToConstant(pop).ToInt32() * kPointerSize;
+    __ Ret(static_cast<int>(pop_size), ecx);
+  } else {
+    Register reg = g.ToRegister(pop);
+    __ pop(ecx);
+    __ lea(esp, Operand(esp, reg, times_4, pop_size));
+    __ jmp(ecx);
+  }
 }