Add x64 disasm regression for BitConverter.SingleToInt32Bits in hot Span<float> loops

src/tests/JIT/Regression/JitBlue/Runtime_130999/Runtime_130999.cs

@@ -0,0 +1,64 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime.CompilerServices;
+using Xunit;
+
+namespace Runtime_130999;
+
+public static class Runtime_130999
+{
+    private static int Expected(float[] input)
+    {
+        int acc = 0;
+
+        foreach (float f in input)
+        {
+            if (f < 0)
+            {
+                acc++;
+            }
+
+            acc += BitConverter.SingleToInt32Bits(f);
+        }
+
+        return acc;
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static int SumBits(Span<float> input)
+    {
+        int acc = 0;
+
+        foreach (float f in input)
+        {
+            if (f < 0)
+            {
+                acc++;
+            }
+
+            // X64-FULL-LINE: vmovd [[REG:[a-z0-9]+]], xmm{{[0-9]+}}
+            // X64-FULL-LINE-NEXT: add {{[a-z0-9]+}}, [[REG]]
+            // X64-NOT: movss dword ptr [rsp
+            acc += BitConverter.SingleToInt32Bits(f);
+        }
+
+        // X64-FULL-LINE: ret
+        return acc;
+    }
+
+    [Fact]
+    public static void Test()
+    {
+        float[] empty = Array.Empty<float>();
+        float[] single = new[] { -2.5f };
+        float[] mixed = new[] { 1.25f, -2.5f, 3.75f, 4.125f };
+        float[] edge = new[] { float.NaN, float.PositiveInfinity, float.NegativeInfinity, float.Epsilon, -float.Epsilon };
+
+        Assert.Equal(Expected(empty), SumBits(empty));
+        Assert.Equal(Expected(single), SumBits(single));
+        Assert.Equal(Expected(mixed), SumBits(mixed));
+        Assert.Equal(Expected(edge), SumBits(edge));
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_130999/Runtime_130999.csproj

@@ -0,0 +1,22 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <!-- Needed for CLRTestEnvironmentVariable -->
+    <RequiresProcessIsolation>true</RequiresProcessIsolation>
+  </PropertyGroup>
+  <PropertyGroup>
+    <Optimize>True</Optimize>
+    <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs">
+      <!-- Enable FileCheck verification of X64-* disasm directives in the test source. -->
+      <HasDisasmCheck>true</HasDisasmCheck>
+    </Compile>
+
+    <CLRTestEnvironmentVariable Include="DOTNET_TieredCompilation" Value="0" />
+    <CLRTestEnvironmentVariable Include="DOTNET_JITMinOpts" Value="0" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="$(TestLibraryProjectPath)" />
+  </ItemGroup>
+</Project>