From 206aa5b280268b011596eb9ae247aca50ce7b9c5 Mon Sep 17 00:00:00 2001
From: Gabe Black <gabeblack@google.com>
Date: Mon, 16 Dec 2019 21:48:36 -0800
Subject: [PATCH] sim: Add a typetraits style mechanism to test for VarArgs.

This family of types can be cumbersome to check for when building
ABI rules. This struct template makes that a little easier.

Change-Id: Ic3a1b8424f8ca04564f8228365371b357f33276c
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/23750
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
---
 src/sim/guest_abi.hh      |  6 ++++++
 src/sim/guest_abi.test.cc | 11 +++++++++++
 2 files changed, 17 insertions(+)

diff --git a/src/sim/guest_abi.hh b/src/sim/guest_abi.hh
index 5432af3f9..9726c49db 100644
--- a/src/sim/guest_abi.hh
+++ b/src/sim/guest_abi.hh
@@ -284,6 +284,12 @@ class VarArgs
     }
 };
 
+template <typename T>
+struct IsVarArgs : public std::false_type {};
+
+template <typename ...Types>
+struct IsVarArgs<VarArgs<Types...>> : public std::true_type {};
+
 template <typename ...Types>
 std::ostream &
 operator << (std::ostream &os, const VarArgs<Types...> &va)
diff --git a/src/sim/guest_abi.test.cc b/src/sim/guest_abi.test.cc
index 506163ee6..bd444aa32 100644
--- a/src/sim/guest_abi.test.cc
+++ b/src/sim/guest_abi.test.cc
@@ -362,3 +362,14 @@ TEST(GuestABI, dumpSimcall)
     std::string dump = dumpSimcall<TestABI_1D>("test", &tc, testIntVoid);
     EXPECT_EQ(dump, "test(0, 11, 2, 13, ...)");
 }
+
+TEST(GuestABI, isVarArgs)
+{
+    EXPECT_TRUE(GuestABI::IsVarArgs<GuestABI::VarArgs<int>>::value);
+    EXPECT_FALSE(GuestABI::IsVarArgs<int>::value);
+    EXPECT_FALSE(GuestABI::IsVarArgs<double>::value);
+    struct FooStruct {};
+    EXPECT_FALSE(GuestABI::IsVarArgs<FooStruct>::value);
+    union FooUnion {};
+    EXPECT_FALSE(GuestABI::IsVarArgs<FooUnion>::value);
+}
-- 
2.30.2