Merge pull request #5394 from erozenfeld/TailCallBug5164

Fix for methods that tail call via helpers

4 files changed, 226 insertions, 6 deletions

diff --git a/src/jit/morph.cpp b/src/jit/morph.cpp
index e09e96baec..1cd9eaba5b 100644
--- a/src/jit/morph.cpp
+++ b/src/jit/morph.cpp
@@ -4875,7 +4875,11 @@ Compiler::fgMakeOutgoingStructArgCopy(GenTreeCall* call,
             if (lvaIsImplicitByRefLocal(varNum))
             {
                 LclVarDsc* varDsc = &lvaTable[varNum];
-                if (varDsc->lvRefCnt == 1 && !fgMightHaveLoop())
+                // JIT_TailCall helper has an implicit assumption that all tail call arguments live
+                // on the caller's frame. If an argument lives on the caller caller's frame, it may get
+                // overwritten if that frame is reused for the tail call. Therefore, we should always copy
+                // struct parameters if they are passed as arguments to a tail call.
+                if (!call->IsTailCallViaHelper() && (varDsc->lvRefCnt == 1) && !fgMightHaveLoop())
                 {
                     varDsc->lvRefCnt = 0;
                     args->gtOp.gtOp1 = lcl;
@@ -4883,13 +4887,8 @@ Compiler::fgMakeOutgoingStructArgCopy(GenTreeCall* call,
                     fp->node = lcl;
 
                     JITDUMP("did not have to make outgoing copy for V%2d", varNum);
-                    varDsc->lvRefCnt = 0;
                     return;
                 }
-                else
-                {
-                    varDsc->lvRefCnt = 0;
-                }
             }
         }
     }
diff --git a/tests/src/JIT/Regression/JitBlue/GitHub_5164/GitHub_5164.il b/tests/src/JIT/Regression/JitBlue/GitHub_5164/GitHub_5164.il
new file mode 100644
index 0000000000..d2cb5bd962
--- /dev/null
+++ b/tests/src/JIT/Regression/JitBlue/GitHub_5164/GitHub_5164.il
@@ -0,0 +1,150 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// The tail call helper JIT_TailCall has an implicit assumption that all
+// arguments of the tail call are allocated on the caller's frame.
+// In this test A tail-calls B and B tail-calls A: Main --> A --> B --> A --> B --> A.
+// In the last B --> A tail call the frame from the preceding A --> B tail call is resused.
+// It's big enough because of the first B --> A tail call.
+// The bug was that the code for B wasn't copying the incoming struct parameter to its frame.
+// The struct lived on the caller's frame and when it was reused for the B --> A tail call,
+// the struct was overwritten.
+
+.assembly extern mscorlib { }
+
+.assembly GitHub_5164 { }
+
+.class public sequential ansi sealed beforefieldinit LargeStruct
+       extends [mscorlib]System.ValueType
+{
+  .field public int64 l1
+  .field public int64 l2
+  .method public hidebysig specialname rtspecialname 
+          instance void  .ctor(int64 l1,
+                               int64 l2) cil managed
+  {
+    // Code size       15 (0xf)
+    .maxstack  8
+    IL_0000:  ldarg.0
+    IL_0001:  ldarg.1
+    IL_0002:  stfld      int64 LargeStruct::l1
+    IL_0007:  ldarg.0
+    IL_0008:  ldarg.2
+    IL_0009:  stfld      int64 LargeStruct::l2
+    IL_000e:  ret
+  } // end of method LargeStruct::.ctor
+
+} // end of class LargeStruct
+
+.class private auto ansi beforefieldinit Test
+       extends [mscorlib]System.Object
+{
+  .method public hidebysig static int32  Main() cil managed
+  {
+    .entrypoint
+    // Code size       48 (0x30)
+    .maxstack  3
+    .locals init (valuetype LargeStruct V_0,
+             valuetype LargeStruct V_1,
+             valuetype LargeStruct V_2)
+    IL_0000:  ldloca.s   V_0
+    IL_0002:  ldc.i4.1
+    IL_0003:  conv.i8
+    IL_0004:  ldc.i4.2
+    IL_0005:  conv.i8
+    IL_0006:  call       instance void LargeStruct::.ctor(int64,
+                                                          int64)
+    IL_000b:  ldloca.s   V_1
+    IL_000d:  ldc.i4.3
+    IL_000e:  conv.i8
+    IL_000f:  ldc.i4.4
+    IL_0010:  conv.i8
+    IL_0011:  call       instance void LargeStruct::.ctor(int64,
+                                                          int64)
+    IL_0016:  ldc.i4.0
+    IL_0017:  ldloc.0
+    IL_0018:  ldloc.1
+    IL_0019:  call       valuetype LargeStruct Test::A(int32,
+                                                       valuetype LargeStruct,
+                                                       valuetype LargeStruct)
+    IL_001e:  stloc.2
+    IL_001f:  ldloca.s   V_2
+    IL_0021:  ldfld      int64 LargeStruct::l1
+    IL_0026:  ldloca.s   V_2
+    IL_0028:  ldfld      int64 LargeStruct::l2
+    IL_002d:  add
+    IL_002e:  conv.i4
+    IL_002f:  ret
+  } // end of method Test::Main
+
+  .method public hidebysig static valuetype LargeStruct 
+          A(int32 count,
+            valuetype LargeStruct s1,
+            valuetype LargeStruct s2) cil managed noinlining
+  {
+    // Code size       58 (0x3a)
+    .maxstack  4
+    .locals init (valuetype LargeStruct V_0)
+    IL_0000:  ldloca.s   V_0
+    IL_0002:  ldarga.s   s1
+    IL_0004:  ldfld      int64 LargeStruct::l1
+    IL_0009:  ldarga.s   s2
+    IL_000b:  ldfld      int64 LargeStruct::l1
+    IL_0010:  add
+    IL_0011:  ldarga.s   s1
+    IL_0013:  ldfld      int64 LargeStruct::l2
+    IL_0018:  ldarga.s   s2
+    IL_001a:  ldfld      int64 LargeStruct::l2
+    IL_001f:  add
+    IL_0020:  call       instance void LargeStruct::.ctor(int64,
+                                                          int64)
+    IL_0025:  ldarg.0
+    IL_0026:  ldc.i4.3
+    IL_0027:  bge.s      IL_0038
+
+    IL_0029:  ldarg.0
+    IL_002a:  ldc.i4.1
+    IL_002b:  add
+    IL_002c:  dup
+    IL_002d:  starg.s    count
+    IL_002f:  ldloc.0
+    IL_0030:  tail.
+    IL_0032:  call       valuetype LargeStruct Test::B(int32,
+                                                       valuetype LargeStruct)
+    IL_0037:  ret
+
+    IL_0038:  ldloc.0
+    IL_0039:  ret
+  } // end of method Test::A
+
+  .method public hidebysig static valuetype LargeStruct 
+          B(int32 count,
+            valuetype LargeStruct s) cil managed noinlining
+  {
+    // Code size       28 (0x1c)
+    .maxstack  3
+    .locals init (valuetype LargeStruct V_0)
+    IL_0000:  ldloca.s   V_0
+    IL_0002:  ldc.i4.1
+    IL_0003:  conv.i8
+    IL_0004:  ldc.i4.s   44
+    IL_0006:  conv.i8
+    IL_0007:  call       instance void LargeStruct::.ctor(int64,
+                                                          int64)
+    IL_000c:  ldarg.0
+    IL_000d:  ldc.i4.1
+    IL_000e:  add
+    IL_000f:  dup
+    IL_0010:  starg.s    count
+    IL_0012:  ldloc.0
+    IL_0013:  ldarg.1
+    IL_0014:  tail.
+    IL_0016:  call       valuetype LargeStruct Test::A(int32,
+                                                       valuetype LargeStruct,
+                                                       valuetype LargeStruct)
+    IL_001b:  ret
+  } // end of method Test::B
+
+} // end of class Test
+
diff --git a/tests/src/JIT/Regression/JitBlue/GitHub_5164/GitHub_5164.ilproj b/tests/src/JIT/Regression/JitBlue/GitHub_5164/GitHub_5164.ilproj
new file mode 100644
index 0000000000..b5d5ee9077
--- /dev/null
+++ b/tests/src/JIT/Regression/JitBlue/GitHub_5164/GitHub_5164.ilproj
@@ -0,0 +1,44 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="12.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.props))\dir.props" />
+  <PropertyGroup>
+    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
+    <AssemblyName>$(MSBuildProjectName)</AssemblyName>
+    <SchemaVersion>2.0</SchemaVersion>
+    <ProjectGuid>{95DFC527-4DC1-495E-97D7-E94EE1F7140D}</ProjectGuid>
+    <OutputType>Exe</OutputType>
+    <AppDesignerFolder>Properties</AppDesignerFolder>
+    <FileAlignment>512</FileAlignment>
+    <ProjectTypeGuids>{786C830F-07A1-408B-BD7F-6EE04809D6DB};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
+    <ReferencePath>$(ProgramFiles)\Common Files\microsoft shared\VSTT	.0\UITestExtensionPackages</ReferencePath>
+    <SolutionDir Condition="$(SolutionDir) == '' Or $(SolutionDir) == '*Undefined*'">..\..\</SolutionDir>
+    <NuGetPackageImportStamp>7a9bfb7d</NuGetPackageImportStamp>
+  </PropertyGroup>
+  <!-- Default configurations to help VS understand the configurations -->
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
+  </PropertyGroup>
+  <ItemGroup>
+    <CodeAnalysisDependentAssemblyPaths Condition=" '$(VS100COMNTOOLS)' != '' " Include="$(VS100COMNTOOLS)..\IDE\PrivateAssemblies">
+      <Visible>False</Visible>
+    </CodeAnalysisDependentAssemblyPaths>
+  </ItemGroup>
+  <PropertyGroup>
+    <DebugType>None</DebugType>
+    <Optimize>True</Optimize>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="GitHub_5164.il" />
+  </ItemGroup>
+  <ItemGroup>
+    <None Include="app.config" />
+  </ItemGroup>
+  <ItemGroup>
+    <Service Include="{82A7F48D-3B50-4B1E-B82E-3ADA8210C358}" />
+  </ItemGroup>
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.targets))\dir.targets" />
+  <PropertyGroup Condition=" '$(MsBuildProjectDirOverride)' != '' ">
+  </PropertyGroup> 
+</Project>
diff --git a/tests/src/JIT/Regression/JitBlue/GitHub_5164/app.config b/tests/src/JIT/Regression/JitBlue/GitHub_5164/app.config
new file mode 100644
index 0000000000..8077c95440
--- /dev/null
+++ b/tests/src/JIT/Regression/JitBlue/GitHub_5164/app.config
@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+  <runtime>
+    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
+      <dependentAssembly>
+        <assemblyIdentity name="System.Runtime" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
+        <bindingRedirect oldVersion="0.0.0.0-4.0.20.0" newVersion="4.0.20.0" />
+      </dependentAssembly>
+      <dependentAssembly>
+        <assemblyIdentity name="System.Text.Encoding" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
+        <bindingRedirect oldVersion="0.0.0.0-4.0.10.0" newVersion="4.0.10.0" />
+      </dependentAssembly>
+      <dependentAssembly>
+        <assemblyIdentity name="System.Threading.Tasks" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
+        <bindingRedirect oldVersion="0.0.0.0-4.0.10.0" newVersion="4.0.10.0" />
+      </dependentAssembly>
+      <dependentAssembly>
+        <assemblyIdentity name="System.IO" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
+        <bindingRedirect oldVersion="0.0.0.0-4.0.10.0" newVersion="4.0.10.0" />
+      </dependentAssembly>
+      <dependentAssembly>
+        <assemblyIdentity name="System.Reflection" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
+        <bindingRedirect oldVersion="0.0.0.0-4.0.10.0" newVersion="4.0.10.0" />
+      </dependentAssembly>
+    </assemblyBinding>
+  </runtime>
+</configuration>
\ No newline at end of file