From d950f21404f6b77cde150ebae5a4d3962cd0dc6e Mon Sep 17 00:00:00 2001
From: sharkautarch <128002472+sharkautarch@users.noreply.github.com>
Date: Wed, 11 Sep 2024 14:25:21 -0400
Subject: [PATCH] constexpr simd vec: fix more runtime issues

---
 glm/detail/simd_constexpr/element.hpp   |  6 ++++--
 glm/detail/simd_constexpr/vec.hpp       | 11 ++++++-----
 test/core/core_c++20_simd_constexpr.cpp |  3 ++-
 3 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/glm/detail/simd_constexpr/element.hpp b/glm/detail/simd_constexpr/element.hpp
index 01908674..43df13c5 100644
--- a/glm/detail/simd_constexpr/element.hpp
+++ b/glm/detail/simd_constexpr/element.hpp
@@ -3,8 +3,10 @@
 namespace glm::detail
 {
 	consteval bool NotEmpty(length_t I, length_t L) { return I <= L; }
-	template <bool IsEmpty, typename T, length_t I, length_t L>
-	struct Element
+	template <bool IsNotEmpty, typename T, length_t I, length_t L>
+	struct Element;
+	template <typename T, length_t I, length_t L> requires (!NotEmpty(I, L))
+	struct Element<false, T, I, L>
 	{
 		constexpr operator auto() {
       return 0;
diff --git a/glm/detail/simd_constexpr/vec.hpp b/glm/detail/simd_constexpr/vec.hpp
index 093cb9bc..a3cb2e7b 100644
--- a/glm/detail/simd_constexpr/vec.hpp
+++ b/glm/detail/simd_constexpr/vec.hpp
@@ -189,17 +189,18 @@ namespace glm
 		
 		// -- Data --
 #define GLM_N [[no_unique_address]]
+#define GLM_MA __attribute__((__may_alias__))
 		template <length_t I>
 		using E = detail::Element<detail::NotEmpty(I,L),T,I,L>;
 		union
 		{
-				struct {
+				GLM_MA struct {
 					union       {          T x,            r,            s; };
-					GLM_N union { GLM_N E<2> y; GLM_N E<2> g; GLM_N E<2> t; };
-					GLM_N union { GLM_N E<3> z; GLM_N E<3> b; GLM_N E<3> p; };
-					GLM_N union { GLM_N E<4> w; GLM_N E<4> a; GLM_N E<4> q; };
+					union { GLM_N E<2> y GLM_MA; GLM_N E<2> g; GLM_N E<2> t; };
+					union { GLM_N E<3> z GLM_MA; GLM_N E<3> b; GLM_N E<3> p; };
+					union { GLM_N E<4> w GLM_MA; GLM_N E<4> a; GLM_N E<4> q; };
 				};
-				data_t data;
+				GLM_MA data_t data;
 		};
 #undef GLM_N
 #				if GLM_CONFIG_SWIZZLE == GLM_SWIZZLE_OPERATOR
diff --git a/test/core/core_c++20_simd_constexpr.cpp b/test/core/core_c++20_simd_constexpr.cpp
index 9d8ad8d3..f4394faa 100644
--- a/test/core/core_c++20_simd_constexpr.cpp
+++ b/test/core/core_c++20_simd_constexpr.cpp
@@ -31,7 +31,8 @@ int main()
 				v1.x;
         avec4 vfin = glm::max(v1, v2) + v3;
 	static_assert(sizeof(vfin)>0);
+	double w = v3.w;
         printf("vfin = %f %f %f %f\n", vfin[0], vfin[1], vfin[2], vfin[3]);
-				printf("v3 = %f %f %f %f\n", v3[0], v3[1], v3[2], v3[3]);
+				printf("v3 = %f %f %f %f\n", v3[0], v3[1], v3.y, w);
 	return 0;
 }