From ad013d59f400a80c320ceb712ed0da7e95d7f7e3 Mon Sep 17 00:00:00 2001
From: Nekotekina <nekotekina@gmail.com>
Date: Wed, 11 Nov 2020 23:59:09 +0300
Subject: [PATCH] atomic.cpp: don't load actual memory on empty mask

It's not an optimization. It just allows some tricks safely.
---
 rpcs3/util/atomic.cpp | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/rpcs3/util/atomic.cpp b/rpcs3/util/atomic.cpp
index f6117f0c0f..d61d061e1d 100644
--- a/rpcs3/util/atomic.cpp
+++ b/rpcs3/util/atomic.cpp
@@ -66,8 +66,10 @@ ptr_cmp(const void* data, u32 _size, __m128i old128, __m128i mask128, atomic_wai
 		u64 old_value = _mm_cvtsi128_si64(old128);
 		u64 mask = _mm_cvtsi128_si64(mask128) & (UINT64_MAX >> ((64 - size * 8) & 63));
 
-		switch (size)
+		// Don't load memory on empty mask
+		switch (mask ? size : 0)
 		{
+		case 0: break;
 		case 1: new_value = reinterpret_cast<const atomic_t<u8>*>(data)->load(); break;
 		case 2: new_value = reinterpret_cast<const atomic_t<u16>*>(data)->load(); break;
 		case 4: new_value = reinterpret_cast<const atomic_t<u32>*>(data)->load(); break;
@@ -169,10 +171,16 @@ ptr_cmp(const void* data, u32 _size, __m128i old128, __m128i mask128, atomic_wai
 	}
 	else if (size == 16 && (flag == op::eq || flag == (op::eq | op_flag::inverse)))
 	{
-		u128 new_value = atomic_storage<u128>::load(*reinterpret_cast<const u128*>(data));
+		u128 new_value = 0;
 		u128 old_value = std::bit_cast<u128>(old128);
 		u128 mask = std::bit_cast<u128>(mask128);
 
+		// Don't load memory on empty mask
+		if (mask) [[likely]]
+		{
+			new_value = atomic_storage<u128>::load(*reinterpret_cast<const u128*>(data));
+		}
+
 		// TODO
 		result = !((old_value ^ new_value) & mask);
 	}