Allow non-constant size for rep stos InitBlk on x86

Fixes DevDiv VSO bug 278371, and adds a test case.

2 files changed, 129 insertions, 0 deletions

diff --git a/tests/src/JIT/Regression/JitBlue/DevDiv_278371/DevDiv_278371.il b/tests/src/JIT/Regression/JitBlue/DevDiv_278371/DevDiv_278371.il
new file mode 100644
index 0000000000..447392e1fd
--- /dev/null
+++ b/tests/src/JIT/Regression/JitBlue/DevDiv_278371/DevDiv_278371.il
@@ -0,0 +1,88 @@
+// 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.
+
+// Test for a bug involving an initblk with a non-constant size,
+// which uses rep movs on x86 (x64 uses a helper call).
+
+.assembly extern legacy library mscorlib {}
+.assembly extern System.Console
+{
+  .publickeytoken = (B0 3F 5F 7F 11 D5 0A 3A )
+  .ver 4:0:0:0
+}
+
+.assembly DevDiv_278371 {}
+
+.class public sequential ansi sealed beforefieldinit S
+       extends [mscorlib]System.ValueType
+{
+  .field public uint32 val
+} // end of class S
+
+.class private auto ansi beforefieldinit Program
+       extends [mscorlib]System.Object
+{
+  .method public hidebysig static void  Init(valuetype S& s,
+                                             int32 size) cil managed noinlining
+  {
+          nop
+          ldarg.0
+          ldc.i4     0xaa
+          ldarg.1
+          initblk
+          ret
+  } // end of method Program::Init
+
+  .method private hidebysig static int32 
+          Main() cil managed
+  {
+    .entrypoint
+    .locals init (valuetype S V_0,
+             bool V_1,
+             int32 V_2)
+              ldloca.s   V_0
+              initobj    S
+              ldloca.s   V_0
+              ldc.i4     4
+              call       void Program::Init(valuetype S&, int32)
+              ldloc.0
+              ldfld      uint32 S::val
+              ldc.i4     0xaaaaaaaa
+              ceq
+              ldc.i4.0
+              ceq
+              stloc.1
+              ldloc.1
+              brfalse.s  L1
+
+              ldstr      "Fail"
+              call       void [mscorlib]System.Console::WriteLine(string)
+              nop
+              ldc.i4.m1
+              stloc.2
+              br.s       L2
+
+    L1:       ldstr      "Pass"
+              call       void [mscorlib]System.Console::WriteLine(string)
+              nop
+              ldc.i4.s   100
+              stloc.2
+
+    L2:       ldloc.2
+              ret
+  } // end of method Program::Main
+
+  .method public hidebysig specialname rtspecialname 
+          instance void  .ctor() cil managed
+  {
+    // Code size       8 (0x8)
+    .maxstack  8
+              ldarg.0
+              call       instance void [mscorlib]System.Object::.ctor()
+              nop
+              ret
+  } // end of method Program::.ctor
+
+} // end of class Program
+
diff --git a/tests/src/JIT/Regression/JitBlue/DevDiv_278371/DevDiv_278371.ilproj b/tests/src/JIT/Regression/JitBlue/DevDiv_278371/DevDiv_278371.ilproj
new file mode 100644
index 0000000000..11cfb62342
--- /dev/null
+++ b/tests/src/JIT/Regression/JitBlue/DevDiv_278371/DevDiv_278371.ilproj
@@ -0,0 +1,41 @@
+<?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\11.0\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="$(VS100COMNTOOLS)..\IDE\PrivateAssemblies">
+      <Visible>False</Visible>
+    </CodeAnalysisDependentAssemblyPaths>
+  </ItemGroup>
+  <PropertyGroup>
+    <DebugType>None</DebugType>
+    <Optimize>True</Optimize>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="DevDiv_278371.il" />
+  </ItemGroup>
+  <ItemGroup>
+    <Service Include="{82A7F48D-3B50-4B1E-B82E-3ADA8210C358}" />
+  </ItemGroup>
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.targets))\dir.targets" />
+  <PropertyGroup Condition=" '$(MsBuildProjectDirOverride)' != '' ">
+  </PropertyGroup> 
+</Project>