vs integration: Use llvm-lib for librarian

[russell.gallop]

Summary

This uses llvm-lib.exe for the librarian instead of Visual Studio
provided lib.exe. Without this it is not possible to create static
libraries with -flto using the plugin.

Original patch by Steven Noonan

This fixes: PR41147

[tycho]

LGTM.

Also this maybe an independent change, but:

One thing I ran into when running with this change locally was that llvm-lib.exe didn't like the /LTCG argument (IIRC it caused a fatal error and llvm-lib.exe refused to continue). This also affected lld-link.exe. I notice that LLVM.Cpp.Common.targets has a big list of options at the bottom that get automatically turned off for compatibility with the LLVM/clang-cl toolchain. Maybe we should add some for llvm-lib.exe and lld-link.exe to drop the /LTCG arguments? Or maybe remap /LTCG -> -flto=thin under the hood where relevant, or something.

[hans]

Thanks! I've rebuilt and published the extension: https://marketplace.visualstudio.com/items?itemName=LLVMExtensions.llvm-toolchain (version 1.0.359557).

I also updated the manifest to add VS 2019 support.

llvm/tools/msbuild/LLVM.Cpp.Common.props

<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
 
   <!-- Find an installed LLVM and set up our paths. -->
   <PropertyGroup>
     <LLVMInstallDir>$(Registry:HKEY_LOCAL_MACHINE\SOFTWARE\LLVM\LLVM)</LLVMInstallDir>
     <LLVMInstallDir Condition="'$(LLVMInstallDir)' == ''">$(Registry:HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\LLVM\LLVM)</LLVMInstallDir>
     <LLVMInstallDir Condition="'$(LLVMInstallDir)' != ''">$(LLVMInstallDir)\</LLVMInstallDir>
     <ClangClExecutable>$(LLVMInstallDir)bin\clang-cl.exe</ClangClExecutable>
     <LldLinkExecutable>$(LLVMInstallDir)bin\lld-link.exe</LldLinkExecutable>
+    <LlvmLibExecutable>$(LLVMInstallDir)bin\llvm-lib.exe</LlvmLibExecutable>
     <UseClangCl>true</UseClangCl>
     <UseLldLink>true</UseLldLink>
+    <UseLlvmLib>true</UseLlvmLib>
   </PropertyGroup>
 
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.WindowsSDK.props" Condition="Exists('$(VCTargetsPath)\Microsoft.Cpp.WindowsSDK.props')"/>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.Common.props" />
 
   <PropertyGroup>
     <!-- Set some paths (such as include paths) that are common to all platforms.  This is the same as what
          the default paths for cl will use.

llvm/tools/msbuild/LLVM.Cpp.Common.targets

 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="$(VCTargetsPath)\Microsoft.CppCommon.targets" />
 
   <PropertyGroup>
     <!-- Set the path to clang-cl executable based on the value of the project-
          level setting.  This has to be done in the .targets file since values
          selected via the settings UI appear in the vcxproj (which is imported
          before the targets file but after the props file) and we need the path
          that the user may have overridden in the UI. -->
     <CLToolExe Condition="$(UseClangCl)">$(ClangClExecutable)</CLToolExe>
     <LinkToolExe Condition="$(UseLldLink)">$(LldLinkExecutable)</LinkToolExe>
+    <LIBToolExe Condition="$(UseLlvmLib)">$(LlvmLibExecutable)</LIBToolExe>
   </PropertyGroup>
 
   <ItemGroup>
     <PropertyPageSchema Include="$(VCTargetsPath)$(LangID)\llvm-general.xml">
       <Context>Project</Context>
     </PropertyPageSchema>
   </ItemGroup>
 

llvm/tools/msbuild/llvm-general.xml

<Rule
   </StringProperty>
 
   <StringProperty Name="LldLinkAdditionalOptions"
                   DisplayName="Additional Linker Options"
                   Description="Additional options to pass to lld-link.  This is essentially the same as General > Linker > Command Line > Additional Options, except that it is safe to put options here that will be rejected by link.exe in case you switch toolchains back and forth."
                   Category="General">
   </StringProperty>
 
+
+  <BoolProperty Name="UseLlvmLib"
+                DisplayName="Use llvm-lib"
+                Description="Use llvm-lib for managing libraries.  If this option is disabled, the Microsoft librarian (lib.exe) will be used instead."
+                Category="General"
+                Default="true">
+  </BoolProperty>
+  <StringProperty Name="LlvmLibExecutable"
+                  DisplayName="llvm-lib Executable"
+                  Description="Specifies the path to llvm-lib.exe."
+                  Category="General"
+                  Default="$(LLVMInstallDir)bin\llvm-lib.exe"
+                  Subtype="file">
+  </StringProperty>
+
+  <StringProperty Name="LlvmLibAdditionalOptions"
+                  DisplayName="Additional Librarian Options"
+                  Description="Additional options to pass to llvm-lib.  This is essentially the same as General > Librarian > Command Line > Additional Options, except that it is safe to put options here that will be rejected by lib.exe in case you switch toolchains back and forth."
+                  Category="General">
+  </StringProperty>
+
 </Rule>