Use SIMD acceleration for audio upsampler (#4410)

* Use SIMD acceleration for audio upsampler filter kernel for a moderate speedup

* Address formatting. Implement AVX2 fast path for high quality resampling in ResamplerHelper

* now really, are we really getting the benefit of inlining 50+ line methods?

* adding unit tests for resampler + upsampler. The upsampler ones fail for some reason

* Fixing upsampler test. Apparently this algo only works at specific ratios

---------

Co-authored-by: Logan Stromberg <lostromb@microsoft.com>

Ryujinx.Tests/Audio/Renderer/Dsp/UpsamplerTests.cs

@@ -0,0 +1,64 @@
+using NUnit.Framework;
+using Ryujinx.Audio.Renderer.Dsp;
+using Ryujinx.Audio.Renderer.Parameter;
+using Ryujinx.Audio.Renderer.Server.Upsampler;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Ryujinx.Tests.Audio.Renderer.Dsp
+{
+    class UpsamplerTests
+    {
+        [Test]
+        public void TestUpsamplerConsistency()
+        {
+            UpsamplerBufferState bufferState = new UpsamplerBufferState();
+            int inputBlockSize = 160;
+            int numInputSamples = 32000;
+            int numOutputSamples = 48000;
+            float inputSampleRate = numInputSamples;
+            float outputSampleRate = numOutputSamples;
+            float[] inputBuffer = new float[numInputSamples + 100];
+            float[] outputBuffer = new float[numOutputSamples + 100];
+            for (int sample = 0; sample < inputBuffer.Length; sample++)
+            {
+                // 440 hz sine wave with amplitude = 0.5f at input sample rate
+                inputBuffer[sample] = MathF.Sin((440 / inputSampleRate) * (float)sample * MathF.PI * 2f) * 0.5f;
+            }
+
+            int inputIdx = 0;
+            int outputIdx = 0;
+            while (inputIdx + inputBlockSize < numInputSamples)
+            {
+                int outputBufLength = (int)Math.Round((float)(inputIdx + inputBlockSize) * outputSampleRate / inputSampleRate) - outputIdx;
+                UpsamplerHelper.Upsample(
+                    outputBuffer.AsSpan(outputIdx),
+                    inputBuffer.AsSpan(inputIdx),
+                    outputBufLength,
+                    inputBlockSize,
+                    ref bufferState);
+
+                inputIdx += inputBlockSize;
+                outputIdx += outputBufLength;
+            }
+
+            float[] expectedOutput = new float[numOutputSamples];
+            float sumDifference = 0;
+            for (int sample = 0; sample < numOutputSamples; sample++)
+            {
+                // 440 hz sine wave with amplitude = 0.5f at output sample rate with an offset of 15
+                expectedOutput[sample] = MathF.Sin((440 / outputSampleRate) * (float)(sample - 15) * MathF.PI * 2f) * 0.5f;
+                sumDifference += Math.Abs(expectedOutput[sample] - outputBuffer[sample]);
+            }
+
+            sumDifference = sumDifference / (float)expectedOutput.Length;
+            // Expect the output to be 98% similar to the expected resampled sine wave
+            Assert.IsTrue(sumDifference < 0.02f);
+        }
+    }
+}