From 03332c340d9e5487bf7f3727abef553235e47f1a Mon Sep 17 00:00:00 2001
From: Nekotekina <nekotekina@gmail.com>
Date: Wed, 10 Mar 2021 15:54:32 +0300
Subject: [PATCH] Implement utils::bless (pointer cast)

Tries to workaround strict aliasing troubles.
Don't confuse with std::bless which works differently.
---
 rpcs3/Emu/Cell/SPUThread.cpp |  2 +-
 rpcs3/Emu/RSX/GL/GLDraw.cpp  |  4 ++--
 rpcs3/util/asm.hpp           | 13 +++++++++++++
 3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/rpcs3/Emu/Cell/SPUThread.cpp b/rpcs3/Emu/Cell/SPUThread.cpp
index c46c5ce7a8..f929d75e68 100644
--- a/rpcs3/Emu/Cell/SPUThread.cpp
+++ b/rpcs3/Emu/Cell/SPUThread.cpp
@@ -2161,7 +2161,7 @@ void spu_thread::do_dma_transfer(spu_thread* _this, const spu_mfc_cmd& args, u8*
 				auto& res = vm::reservation_acquire(eal);
 
 				// Lock each bit corresponding to a byte being written, using some free space in reservation memory
-				auto* bits = reinterpret_cast<atomic_t<u128>*>(vm::g_reservations + ((eal & 0xff80) / 2 + 16));
+				auto* bits = utils::bless<atomic_t<u128>>(vm::g_reservations + ((eal & 0xff80) / 2 + 16));
 
 				// Get writing mask
 				const u128 wmask = (~u128{} << (eal & 127)) & (~u128{} >> (127 - ((eal + size0 - 1) & 127)));
diff --git a/rpcs3/Emu/RSX/GL/GLDraw.cpp b/rpcs3/Emu/RSX/GL/GLDraw.cpp
index 75b9c5553b..527e389b70 100644
--- a/rpcs3/Emu/RSX/GL/GLDraw.cpp
+++ b/rpcs3/Emu/RSX/GL/GLDraw.cpp
@@ -493,7 +493,7 @@ void GLGSRender::emit_geometry(u32 sub_index)
 			m_scratch_buffer.resize(draw_count * 24);
 			GLint* firsts = reinterpret_cast<GLint*>(m_scratch_buffer.data());
 			GLsizei* counts = (firsts + draw_count);
-			const GLvoid** offsets = reinterpret_cast<const GLvoid**>(counts + draw_count);
+			const GLvoid** offsets = utils::bless<const GLvoid*>(counts + draw_count);
 
 			u32 first = 0;
 			u32 dst_index = 0;
@@ -560,7 +560,7 @@ void GLGSRender::emit_geometry(u32 sub_index)
 			m_scratch_buffer.resize(draw_count * 16);
 
 			GLsizei *counts = reinterpret_cast<GLsizei*>(m_scratch_buffer.data());
-			const GLvoid** offsets = reinterpret_cast<const GLvoid**>(counts + draw_count);
+			const GLvoid** offsets = utils::bless<const GLvoid*>(counts + draw_count);
 			int dst_index = 0;
 
 			for (const auto &range : subranges)
diff --git a/rpcs3/util/asm.hpp b/rpcs3/util/asm.hpp
index a31b5c6102..ab4170061e 100644
--- a/rpcs3/util/asm.hpp
+++ b/rpcs3/util/asm.hpp
@@ -390,6 +390,19 @@ namespace utils
 
 		return static_cast<T>(value / align + (value > 0 ? T{(value % align) > (align / 2)} : 0 - T{(value % align) < (align / 2)}));
 	}
+
+	// Hack. Pointer cast util to workaround UB. Use with extreme care.
+	template <typename T, typename U>
+	[[nodiscard]] T* bless(U* ptr)
+	{
+#ifdef _MSC_VER
+		return (T*)ptr;
+#else
+		T* result;
+		__asm__("movq %1, %0;" : "=r" (result) : "r" (ptr) : "memory");
+		return result;
+#endif
+	}
 } // namespace utils
 
 using utils::busy_wait;