From 23c844b2aa84a65e573dcc023d19b8f5294a8baf Mon Sep 17 00:00:00 2001
From: jhorv <38920027+jhorv@users.noreply.github.com>
Date: Sat, 11 Mar 2023 15:05:48 -0500
Subject: Misc performance tweaks (#4509)

* use Array.Empty() where instead of allocating new zero-length arrays

* structure for loops in a way that the JIT will elide array/Span bounds checking

* avoiding function calls in for loop condition tests

* avoid LINQ in a hot path

* conform with code style

* fix mistake in GetNextWaitingObject()

* fix GetNextWaitingObject() possibility of returning null if all list items have TimePoint == long.MaxValue

* make GetNextWaitingObject() behave FIFO behavior for multiple items with the same TimePoint
---
 Ryujinx.HLE/HOS/Ipc/IpcHandleDesc.cs               |  4 ++--
 Ryujinx.HLE/HOS/Ipc/IpcMessage.cs                  |  5 +++--
 Ryujinx.HLE/HOS/Kernel/Common/KTimeManager.cs      | 23 ++++++++++++++++++++--
 .../Time/TimeZone/TimeZoneContentManager.cs        |  2 +-
 4 files changed, 27 insertions(+), 7 deletions(-)

(limited to 'Ryujinx.HLE/HOS')

diff --git a/Ryujinx.HLE/HOS/Ipc/IpcHandleDesc.cs b/Ryujinx.HLE/HOS/Ipc/IpcHandleDesc.cs
index 439590e0..e6ed4613 100644
--- a/Ryujinx.HLE/HOS/Ipc/IpcHandleDesc.cs
+++ b/Ryujinx.HLE/HOS/Ipc/IpcHandleDesc.cs
@@ -49,12 +49,12 @@ namespace Ryujinx.HLE.HOS.Ipc
 
         public static IpcHandleDesc MakeCopy(params int[] handles)
         {
-            return new IpcHandleDesc(handles, new int[0]);
+            return new IpcHandleDesc(handles, Array.Empty<int>());
         }
 
         public static IpcHandleDesc MakeMove(params int[] handles)
         {
-            return new IpcHandleDesc(new int[0], handles);
+            return new IpcHandleDesc(Array.Empty<int>(), handles);
         }
 
         public byte[] GetBytes()
diff --git a/Ryujinx.HLE/HOS/Ipc/IpcMessage.cs b/Ryujinx.HLE/HOS/Ipc/IpcMessage.cs
index 09e237fe..55044da4 100644
--- a/Ryujinx.HLE/HOS/Ipc/IpcMessage.cs
+++ b/Ryujinx.HLE/HOS/Ipc/IpcMessage.cs
@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
@@ -132,7 +133,7 @@ namespace Ryujinx.HLE.HOS.Ipc
                 word0 |= (ReceiveBuff.Count  & 0xf) << 24;
                 word0 |= (ExchangeBuff.Count & 0xf) << 28;
 
-                byte[] handleData = new byte[0];
+                byte[] handleData = Array.Empty<byte>();
 
                 if (HandleDesc != null)
                 {
@@ -202,7 +203,7 @@ namespace Ryujinx.HLE.HOS.Ipc
                 word0 |= (ReceiveBuff.Count & 0xf) << 24;
                 word0 |= (ExchangeBuff.Count & 0xf) << 28;
 
-                byte[] handleData = new byte[0];
+                byte[] handleData = Array.Empty<byte>();
 
                 if (HandleDesc != null)
                 {
diff --git a/Ryujinx.HLE/HOS/Kernel/Common/KTimeManager.cs b/Ryujinx.HLE/HOS/Kernel/Common/KTimeManager.cs
index 020048f4..030a314f 100644
--- a/Ryujinx.HLE/HOS/Kernel/Common/KTimeManager.cs
+++ b/Ryujinx.HLE/HOS/Kernel/Common/KTimeManager.cs
@@ -1,7 +1,6 @@
 using Ryujinx.Common;
 using System;
 using System.Collections.Generic;
-using System.Linq;
 using System.Threading;
 
 namespace Ryujinx.HLE.HOS.Kernel.Common
@@ -86,7 +85,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Common
                     {
                         Interlocked.Exchange(ref _enforceWakeupFromSpinWait, 0);
 
-                        next = _waitingObjects.OrderBy(x => x.TimePoint).FirstOrDefault();
+                        next = GetNextWaitingObject();
                     }
 
                     if (next != null)
@@ -140,6 +139,26 @@ namespace Ryujinx.HLE.HOS.Kernel.Common
             }
         }
 
+        private WaitingObject GetNextWaitingObject()
+        {
+            WaitingObject selected = null;
+            
+            long lowestTimePoint = long.MaxValue;
+
+            for (int index = _waitingObjects.Count - 1; index >= 0; index--)
+            {
+                WaitingObject current = _waitingObjects[index];
+
+                if (current.TimePoint <= lowestTimePoint)
+                {
+                    selected = current;
+                    lowestTimePoint = current.TimePoint;
+                }
+            }
+
+            return selected;
+        }
+
         public static long ConvertNanosecondsToMilliseconds(long time)
         {
             time /= 1000000;
diff --git a/Ryujinx.HLE/HOS/Services/Time/TimeZone/TimeZoneContentManager.cs b/Ryujinx.HLE/HOS/Services/Time/TimeZone/TimeZoneContentManager.cs
index 69ed56d4..9367024e 100644
--- a/Ryujinx.HLE/HOS/Services/Time/TimeZone/TimeZoneContentManager.cs
+++ b/Ryujinx.HLE/HOS/Services/Time/TimeZone/TimeZoneContentManager.cs
@@ -233,7 +233,7 @@ namespace Ryujinx.HLE.HOS.Services.Time.TimeZone
                 // If the location name is too long, error out.
                 if (locationName.Length > 0x24)
                 {
-                    outLocationNameArray = new string[0];
+                    outLocationNameArray = Array.Empty<string>();
 
                     return ResultCode.LocationNameTooLong;
                 }
-- 
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