From b57a9c31f049a612c73fe321edb1988cf5293d1b Mon Sep 17 00:00:00 2001
From: Nekotekina <nekotekina@gmail.com>
Date: Mon, 12 Oct 2020 15:09:39 +0300
Subject: [PATCH] Implement utils::tx_start (for TSX)

Implement utils::tx_abort helper.
---
 Utilities/asm.h | 74 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)

diff --git a/Utilities/asm.h b/Utilities/asm.h
index 951dd2fd2a..6f972040fa 100644
--- a/Utilities/asm.h
+++ b/Utilities/asm.h
@@ -4,6 +4,80 @@
 
 namespace utils
 {
+	// Transaction helper (Max = max attempts) (result = pair of success and op result, which is only meaningful on success)
+	template <uint Max = 10, typename F, typename R = std::invoke_result_t<F>>
+	inline auto tx_start(F op)
+	{
+		uint status = -1;
+
+		for (uint i = 0; i < Max; i++)
+		{
+#ifndef _MSC_VER
+			__asm__ goto ("xbegin %l[retry];" ::: "memory" : retry);
+#else
+			status = _xbegin();
+
+			if (status != _XBEGIN_STARTED) [[unlikely]]
+			{
+				goto retry;
+			}
+#endif
+
+			if constexpr (std::is_void_v<R>)
+			{
+				std::invoke(op);
+#ifndef _MSC_VER
+				__asm__ volatile ("xend;" ::: "memory");
+#else
+				_xend();
+#endif
+				return true;
+			}
+			else
+			{
+				auto result = std::invoke(op);
+#ifndef _MSC_VER
+				__asm__ volatile ("xend;" ::: "memory");
+#else
+				_xend();
+#endif
+				return std::make_pair(true, std::move(result));
+			}
+
+			retry:
+#ifndef _MSC_VER
+			__asm__ volatile ("movl %%eax, %0;" : "=r" (status) :: "memory");
+#endif
+			if (!(status & _XABORT_RETRY)) [[unlikely]]
+			{
+				// In order to abort transaction, tx_abort() can be used, so there is no need for "special" return value
+				break;
+			}
+		}
+
+		if constexpr (std::is_void_v<R>)
+		{
+			return false;
+		}
+		else
+		{
+			return std::make_pair(false, R());
+		}
+	};
+
+	// Special function to abort transaction
+	[[noreturn]] FORCE_INLINE void tx_abort()
+	{
+#ifndef _MSC_VER
+		__asm__ volatile ("xabort $0;" ::: "memory");
+		__builtin_unreachable();
+#else
+		_xabort(0);
+		__assume(0);
+#endif
+	}
+
+
 // Rotate helpers
 #if defined(__GNUG__)