From 0c7f131ed2ce008e8d17aa8530f790f934242713 Mon Sep 17 00:00:00 2001
From: Gabe Black <gabeblack@google.com>
Date: Mon, 27 Apr 2020 13:44:42 -0700
Subject: [PATCH] arm: Fix some bugs in the aapcs64 implementation.

The templates which checked for short vectors, and our approximation of
HFA, HVA and HXA types were not correct. This change actually simplifies
them along with getting them to produce correct results. In the case of
HXA, there was a logic bug where an && was used where an || was
intended.

There may still be bugs in the actual collection of arguments and
setting of return values since those aspects are harder to test.

Change-Id: Ice3177205a98c678ecb43ba600813b3909c44e6b
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/28267
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
---
 src/arch/arm/aapcs64.hh | 46 ++++++++++++++---------------------------
 1 file changed, 16 insertions(+), 30 deletions(-)

diff --git a/src/arch/arm/aapcs64.hh b/src/arch/arm/aapcs64.hh
index 203846d43..30597f59e 100644
--- a/src/arch/arm/aapcs64.hh
+++ b/src/arch/arm/aapcs64.hh
@@ -70,24 +70,17 @@ namespace GuestABI
 
 // A short vector is a machine type that is composed of repeated instances of
 // one fundamental integral or floating- point type. It may be 8 or 16 bytes
-// in total size. We represent it here as an opaque blob of data with an
-// appropriate alignment requirement.
+// in total size.
 
-template <typename T, std::size_t count, typename Enabled=void>
-using Aapcs64ShortVectorCandidate =
-    alignas(sizeof(T) * count) uint8_t [sizeof(T) * count];
-
-template <typename T, std::size_t count>
-using Aapcs64ShortVector = Aapcs64ShortVectorCandidate<T, count,
-    typename std::enable_if<
-        (std::is_integral<T>::value || std::is_floating_point<T>::value) &&
-        (sizeof(T) * count == 8 || sizeof(T) * count == 16)>::type>;
-
-template <typename T>
+template <typename T, typename Enabled=void>
 struct IsAapcs64ShortVector : public std::false_type {};
 
 template <typename E, size_t N>
-struct IsAapcs64ShortVector<Aapcs64ShortVector<E, N>> : public std::true_type
+struct IsAapcs64ShortVector<E[N],
+    typename std::enable_if<
+        (std::is_integral<E>::value || std::is_floating_point<E>::value) &&
+        (sizeof(E) * N == 8 || sizeof(E) * N == 16)>::type> :
+        public std::true_type
 {};
 
 /*
@@ -114,38 +107,31 @@ struct IsAapcs64Composite<T, typename std::enable_if<
 // we can't actually detect that or manipulate that with templates. Instead,
 // we approximate that by detecting only arrays with that property.
 
-template <typename T, std::size_t count, typename Enabled=void>
-using Aapcs64HomogeneousAggregate = T[count];
-
 // An Homogeneous Floating-Point Aggregate (HFA) is an Homogeneous Aggregate
 // with a Fundemental Data Type that is a Floating-Point type and at most four
 // uniquely addressable members.
 
-template <typename T, std::size_t count>
-using Aapcs64Hfa = Aapcs64HomogeneousAggregate<T, count,
-      typename std::enable_if<std::is_floating_point<T>::value &&
-                              count <= 4>::type>;
-
 template <typename T, typename Enabled=void>
 struct IsAapcs64Hfa : public std::false_type {};
 
 template <typename E, size_t N>
-struct IsAapcs64Hfa<E[N], Aapcs64Hfa<E, N>> : public std::true_type {};
+struct IsAapcs64Hfa<E[N],
+    typename std::enable_if<std::is_floating_point<E>::value &&
+    N <= 4>::type> : public std::true_type
+{};
 
 // An Homogeneous Short-Vector Aggregate (HVA) is an Homogeneous Aggregate with
 // a Fundamental Data Type that is a Short-Vector type and at most four
 // uniquely addressable members.
 
-template <typename T, std::size_t count>
-using Aapcs64Hva = Aapcs64HomogeneousAggregate<T, count,
-      typename std::enable_if<IsAapcs64ShortVector<T>::value &&
-                              count <= 4>::type>;
-
 template <typename T, typename Enabled=void>
 struct IsAapcs64Hva : public std::false_type {};
 
 template <typename E, size_t N>
-struct IsAapcs64Hva<E[N], Aapcs64Hva<E, N>> : public std::true_type {};
+struct IsAapcs64Hva<E[N],
+    typename std::enable_if<IsAapcs64ShortVector<E>::value &&
+    N <= 4>::type> : public std::true_type
+{};
 
 // A shorthand to test if a type is an HVA or an HFA.
 template <typename T, typename Enabled=void>
@@ -153,7 +139,7 @@ struct IsAapcs64Hxa : public std::false_type {};
 
 template <typename T>
 struct IsAapcs64Hxa<T, typename std::enable_if<
-    IsAapcs64Hfa<T>::value && IsAapcs64Hva<T>::value>::type> :
+    IsAapcs64Hfa<T>::value || IsAapcs64Hva<T>::value>::type> :
     public std::true_type
 {};
 
-- 
2.30.2