From 776b2bf39f3ef429d9e92633d3de4337f8b42bfc Mon Sep 17 00:00:00 2001
From: Eugene Rozenfeld <erozen@microsoft.com>
Date: Fri, 15 Sep 2017 13:34:21 -0700
Subject: [PATCH] Fix check for recursive call in the importer. (#13990)

The check for recursive call was incorrect when processing an inlineee.
The change had no diffs with jit-diff --frameworks --tests so I added a test where
this change results in a codegen diff: the call to C is inlined with this change but
is not inlined without it.
---
 src/jit/compiler.h                                 |  7 +++-
 src/jit/importer.cpp                               |  2 +-
 .../JIT/opt/FastTailCall/FastTailCallInlining.cs   | 39 +++++++++++++++++++
 .../opt/FastTailCall/FastTailCallInlining.csproj   | 45 ++++++++++++++++++++++
 4 files changed, 91 insertions(+), 2 deletions(-)
 create mode 100644 tests/src/JIT/opt/FastTailCall/FastTailCallInlining.cs
 create mode 100644 tests/src/JIT/opt/FastTailCall/FastTailCallInlining.csproj

diff --git a/src/jit/compiler.h b/src/jit/compiler.h
index 86917d9..7c99a69 100644
--- a/src/jit/compiler.h
+++ b/src/jit/compiler.h
@@ -2218,7 +2218,12 @@ public:
     // Note when inlining, this looks for calls back to the root method.
     bool gtIsRecursiveCall(GenTreeCall* call)
     {
-        return (call->gtCallMethHnd == impInlineRoot()->info.compMethodHnd);
+        return gtIsRecursiveCall(call->gtCallMethHnd);
+    }
+
+    bool gtIsRecursiveCall(CORINFO_METHOD_HANDLE callMethodHandle)
+    {
+        return (callMethodHandle == impInlineRoot()->info.compMethodHnd);
     }
 
     //-------------------------------------------------------------------------
diff --git a/src/jit/importer.cpp b/src/jit/importer.cpp
index 580e2b8..90d1618 100644
--- a/src/jit/importer.cpp
+++ b/src/jit/importer.cpp
@@ -6993,7 +6993,7 @@ var_types Compiler::impImportCall(OPCODE                  opcode,
         exactContextNeedsRuntimeLookup = callInfo->exactContextNeedsRuntimeLookup == TRUE;
 
         // Recursive call is treated as a loop to the begining of the method.
-        if (methHnd == info.compMethodHnd)
+        if (gtIsRecursiveCall(methHnd))
         {
 #ifdef DEBUG
             if (verbose)
diff --git a/tests/src/JIT/opt/FastTailCall/FastTailCallInlining.cs b/tests/src/JIT/opt/FastTailCall/FastTailCallInlining.cs
new file mode 100644
index 0000000..81ffd72
--- /dev/null
+++ b/tests/src/JIT/opt/FastTailCall/FastTailCallInlining.cs
@@ -0,0 +1,39 @@
+// 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.
+
+using System;
+using System.Runtime.CompilerServices;
+
+public class Test
+{
+   public static int Main()
+   {
+       A(2);
+       return 100;
+   }
+      
+   public static void A(int i)
+   {
+       if (i > 0)
+       {
+           B(--i);
+       }
+   }  
+
+   [MethodImpl(MethodImplOptions.AggressiveInlining)]
+   public static void B(int i)
+   {
+       C(i);
+       A(--i);
+   }
+
+   public static void C(int i)
+   {
+       Console.WriteLine("In C");
+       if (i==0)
+       {
+           Console.WriteLine("In C");
+       }
+   }
+}
diff --git a/tests/src/JIT/opt/FastTailCall/FastTailCallInlining.csproj b/tests/src/JIT/opt/FastTailCall/FastTailCallInlining.csproj
new file mode 100644
index 0000000..4481224
--- /dev/null
+++ b/tests/src/JIT/opt/FastTailCall/FastTailCallInlining.csproj
@@ -0,0 +1,45 @@
+<?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>$(MSBuildProjectName)</AssemblyName>
+    <SchemaVersion>2.0</SchemaVersion>
+    <ProjectGuid>{95DFC527-4DC1-495E-97D7-E94EE1F7140D}</ProjectGuid>
+    <OutputType>Exe</OutputType>
+    <ProjectTypeGuids>{786C830F-07A1-408B-BD7F-6EE04809D6DB};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
+    <SolutionDir Condition="$(SolutionDir) == '' Or $(SolutionDir) == '*Undefined*'">..\..\</SolutionDir>
+    <IlasmRoundTrip>true</IlasmRoundTrip>
+  </PropertyGroup>
+  <!-- Default configurations to help VS understand the configurations -->
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
+  </PropertyGroup>
+  <ItemGroup>
+    <CodeAnalysisDependentAssemblyPaths Condition=" '$(VS100COMNTOOLS)' != '' " Include="$(VS100COMNTOOLS)..\IDE\PrivateAssemblies">
+      <Visible>False</Visible>
+    </CodeAnalysisDependentAssemblyPaths>
+  </ItemGroup>
+  <PropertyGroup>
+    <!-- Set to 'Full' if the Debug? column is marked in the spreadsheet. Leave blank otherwise. -->
+    <DebugType>None</DebugType>
+    <NoLogo>True</NoLogo>
+    <NoStandardLib>True</NoStandardLib>
+    <Noconfig>True</Noconfig>
+    <Optimize>True</Optimize>
+    <JitOptimizationSensitive>True</JitOptimizationSensitive>
+    <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
+    <DefineConstants>$(DefineConstants);CORECLR</DefineConstants>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="FastTailCallInlining.cs" />
+  </ItemGroup>
+  <ItemGroup>
+    <Service Include="{82A7F48D-3B50-4B1E-B82E-3ADA8210C358}" />
+  </ItemGroup>
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.targets))\dir.targets" />
+  <PropertyGroup Condition=" '$(MsBuildProjectDirOverride)' != '' ">
+  </PropertyGroup> 
+</Project>
-- 
2.7.4