Fix reporting of live var ranges after callf+always pairs

src/coreclr/jit/lsra.cpp

@@ -1348,10 +1348,22 @@ void LinearScan::recordVarLocationsAtStartOfBB(BasicBlock* bb)
             count++;
 
 #ifdef USING_VARIABLE_LIVE_RANGE
-            if (bb->bbPrev != nullptr && VarSetOps::IsMember(compiler, bb->bbPrev->bbLiveOut, varIndex))
+            BasicBlock* prevReportedBlock = bb->bbPrev;
+            if (bb->bbPrev != nullptr && bb->bbPrev->isBBCallAlwaysPairTail())
             {
-                // varDsc was alive on previous block end ("bb->bbPrev->bbLiveOut"), so it has an open
-                // "VariableLiveRange" which should change to be according "getInVarToRegMap"
+                // For callf+always pair we generate the code for the always
+                // block in genCallFinally and skip it, so we don't report
+                // anything for it (it has only trivial instructions, so that
+                // does not matter much). So whether we need to rehome or not
+                // depends on what we reported at the end of the callf block.
+                prevReportedBlock = bb->bbPrev->bbPrev;
+            }
+
+            if (prevReportedBlock != nullptr && VarSetOps::IsMember(compiler, prevReportedBlock->bbLiveOut, varIndex))
+            {
+                // varDsc was alive on previous block end so it has an open
+                // "VariableLiveRange" which should change to be according to
+                // "getInVarToRegMap"
                 compiler->codeGen->getVariableLiveKeeper()->siUpdateVariableLiveRange(varDsc, varNum);
             }
 #endif // USING_VARIABLE_LIVE_RANGE

src/tests/JIT/Regression/JitBlue/Runtime_57752/Runtime_57752_1.cs

@@ -0,0 +1,95 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+// Generated by Fuzzlyn v1.3 on 2021-08-19 15:47:06
+// Run on .NET 6.0.0-dev on X64 Windows
+// Seed: 16489483397161801783
+// Reduced from 251.9 KiB to 1.7 KiB in 02:46:36
+// 
+// Assert failure(PID 27840 [0x00006cc0], Thread: 1464 [0x05b8]): Assertion failed '!m_VariableLiveRanges->back().m_EndEmitLocation.Valid()' in 'Program:M51(System.Boolean[],System.UInt16[],System.Boolean[],long,System.Int32[],byref)' during 'Generate code' (IL size 140)
+// 
+//     File: D:\dev\dotnet\runtime\src\coreclr\jit\codegencommon.cpp Line: 11990
+//     Image: D:\dev\Fuzzlyn\Fuzzlyn\publish\windows-x64\Fuzzlyn.exe
+// 
+// 
+public class Runtime_57752_1
+{
+    internal static I s_rt;
+    internal static long s_10;
+    internal static bool[] s_27 = new[]{true};
+    internal static short s_28;
+    internal static bool s_33;
+    internal static bool s_53;
+    internal static int[][] s_56;
+    public static int Main()
+    {
+        s_rt = new C();
+        var vr9 = new ushort[]{0};
+        var vr10 = new bool[]{true};
+        var vr11 = new int[]{0};
+        M51(s_27, vr9, vr10, 0, vr11, ref s_28);
+        return 100;
+    }
+
+    internal static void M51(bool[] arg0, ushort[] arg5, bool[] arg9, ulong arg10, int[] arg11, ref short arg12)
+    {
+        if (arg0[0])
+        {
+            if (arg0[0])
+            {
+                arg11[0] = arg11[0];
+            }
+            else
+            {
+                try
+                {
+                }
+                finally
+                {
+                    arg9[0] = arg9[0];
+                }
+
+                try
+                {
+                    arg0[0] = true;
+                }
+                finally
+                {
+                    for (int var4 = 0; var4 < 2; var4++)
+                    {
+                        s_53 = arg0[0];
+                        arg10 = 0;
+                        ushort var6 = arg5[0];
+                        long var8 = 0;
+                        s_rt.Write(s_56[0][0]);
+                        s_rt.Write(var8);
+                    }
+
+                    s_33 = false;
+                    try
+                    {
+                        s_10 = s_10;
+                    }
+                    finally
+                    {
+                        arg12 = ref arg12;
+                    }
+                }
+            }
+
+            bool vr1 = arg9[0];
+        }
+    }
+}
+
+public interface I
+{
+    void Write<T>(T val);
+}
+
+public class C : I
+{
+    public void Write<T>(T val)
+    {
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_57752/Runtime_57752_1.csproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
+  </PropertyGroup>
+  <PropertyGroup>
+    <DebugType>None</DebugType>
+    <Optimize>True</Optimize>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>

src/tests/JIT/Regression/JitBlue/Runtime_57752/Runtime_57752_2.cs

@@ -0,0 +1,57 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+// Generated by Fuzzlyn v1.3 on 2021-08-23 02:35:43
+// Run on .NET 6.0.0-dev on X64 Windows
+// Seed: 13788434105727734599
+// Reduced from 365.1 KiB to 0.9 KiB in 02:25:35
+// Exits with error:
+// 
+// Assert failure(PID 11828 [0x00002e34], Thread: 24792 [0x60d8]): Assertion failed 'm_VariableLiveRanges != nullptr && !m_VariableLiveRanges->empty()' in 'Program:M53(byref,byref)' during 'Generate code' (IL size 177)
+// 
+//     File: D:\dev\dotnet\runtime\src\coreclr\jit\codegencommon.cpp Line: 11987
+//     Image: D:\dev\Fuzzlyn\Fuzzlyn\publish\windows-x64\Fuzzlyn.exe
+// 
+// 
+public class Runtime_57752_2
+{
+    internal static ulong s_46;
+    public static int Main()
+    {
+        M53(ref s_46, ref s_46);
+        return 100;
+    }
+
+    internal static void M53(ref ulong arg0, ref ulong arg1)
+    {
+        int var11 = default(int);
+        for (int var0 = 0; var0 < 1; var0++)
+        {
+            return;
+        }
+
+        try
+        {
+            bool vr0 = arg1 >= 0;
+            bool vr6 = vr0;
+        }
+        finally
+        {
+            for (int var2 = 0; var2 < -1; var2++)
+            {
+            }
+
+            try
+            {
+            }
+            finally
+            {
+                System.Console.WriteLine(var11);
+            }
+
+            var vr7 = new uint[][]{new uint[]{0}, new uint[]{0}, new uint[]{0}, new uint[]{0}, new uint[]{0}, new uint[]{0}, new uint[]{0}, new uint[]{0}, new uint[]{0}, new uint[]{0}};
+        }
+
+        System.Console.WriteLine(arg0);
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_57752/Runtime_57752_2.csproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
+  </PropertyGroup>
+  <PropertyGroup>
+    <DebugType>None</DebugType>
+    <Optimize>True</Optimize>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>