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Prefer lld in NativeAot when using clang #85478

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Prefer lld in NativeAot when using clang #85478

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a2ab683
Prefer lld in NativeAot when using clang
sbomer Apr 27, 2023
a1d7be8
Remove LinkerFlavor settings from runtime build
sbomer Apr 27, 2023
c21d315
Fix logic to work with overridden CppLinker
sbomer Apr 28, 2023
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1 change: 0 additions & 1 deletion eng/testing/tests.singlefile.targets
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Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,6 @@
<IlcSdkPath>$(CoreCLRAotSdkDir)</IlcSdkPath>
<IlcFrameworkPath>$(NetCoreAppCurrentTestHostSharedFrameworkPath)</IlcFrameworkPath>
<IlcFrameworkNativePath>$(NetCoreAppCurrentTestHostSharedFrameworkPath)</IlcFrameworkNativePath>
<LinkerFlavor Condition="'$(TargetOS)' == 'linux'">lld</LinkerFlavor>
<NoWarn>$(NoWarn);IL1005;IL2105;IL3000;IL3001;IL3002;IL3003</NoWarn>
<TrimMode>partial</TrimMode>
<SuppressTrimAnalysisWarnings>true</SuppressTrimAnalysisWarnings>
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14 changes: 11 additions & 3 deletions src/coreclr/nativeaot/BuildIntegration/Microsoft.NETCore.Native.Unix.targets
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Expand Up @@ -22,7 +22,6 @@ The .NET Foundation licenses this file to you under the MIT license.
<DsymUtilOptions Condition="'$(_IsApplePlatform)' == 'true'">--flat</DsymUtilOptions>
<_SymbolPrefix Condition="'$(_IsApplePlatform)' == 'true'">_</_SymbolPrefix>
<LinkerFlavor Condition="'$(LinkerFlavor)' == '' and '$(_targetOS)' == 'freebsd'">lld</LinkerFlavor>
<LinkerFlavor Condition="'$(LinkerFlavor)' == '' and '$(_targetOS)' == 'linux'">bfd</LinkerFlavor>
</PropertyGroup>

<Target Name="SetupOSSpecificProps" DependsOnTargets="$(IlcDynamicBuildPropertyDependencies)">
Expand Down Expand Up @@ -104,7 +103,6 @@ The .NET Foundation licenses this file to you under the MIT license.
</ItemGroup>

<ItemGroup>
<LinkerArg Include="-fuse-ld=$(LinkerFlavor)" Condition="'$(LinkerFlavor)' != ''" />
<LinkerArg Include="@(NativeLibrary)" />
<LinkerArg Include="--sysroot=$(SysRoot)" Condition="'$(SysRoot)' != ''" />
<LinkerArg Include="--target=$(TargetTriple)" Condition="'$(_IsApplePlatform)' != 'true' and '$(TargetTriple)' != ''" />
Expand Down Expand Up @@ -180,11 +178,21 @@ The .NET Foundation licenses this file to you under the MIT license.
<Error Condition="'$(_WhereLinker)' != '0' and '$(CppCompilerAndLinkerAlternative)' == '' and '$(_IsApplePlatform)' != 'true'"
Text="Requested linker ('$(CppLinker)') not found in PATH." />

<Exec Command="&quot;$(CppLinker)&quot; -fuse-ld=lld -Wl,--version" Condition="'$(LinkerFlavor)' == 'lld'" IgnoreExitCode="true" StandardOutputImportance="Low" ConsoleToMSBuild="true">
<Exec Command="&quot;$(CppLinker)&quot; -fuse-ld=lld -Wl,--version" Condition="'$(LinkerFlavor)' == 'lld' or ('$(LinkerFlavor)' == '' and $(CppCompilerAndLinker.Contains('clang')))"
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@am11 am11 Apr 28, 2023 •
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Suggested change
<Exec Command="&quot;$(CppLinker)&quot; -fuse-ld=lld -Wl,--version" Condition="'$(LinkerFlavor)' == 'lld' or ('$(LinkerFlavor)' == '' and $(CppCompilerAndLinker.Contains('clang')))"
<Exec Command="&quot;$(CppLinker)&quot; -fuse-ld=lld -Wl,--version" Condition="'$(LinkerFlavor)' == 'lld'" IgnoreExitCode="true" StandardOutputImportance="Low" ConsoleToMSBuild="true">

Revert this line: this is not correct. Before we were checking the --version regardless of LinkerFlavor emptiness. Which means FreeBSD and user-supplied -p:LinkkerFlavor cases were also considered.

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We're still checking the version when LinkerFlavor is lld, like before, whether user-supplied or due to the FreeBSD default above. Maybe I'm missing something - could you give an example?

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@am11 am11 Apr 28, 2023 •
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When LinkerFlavor is lld, we will always check the version. Which means _LinkerVersion can't be empty if lld exists and changes made in src/coreclr/nativeaot/BuildIntegration/Microsoft.NETCore.Native.targets are not needed, right?

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It's possible that LinkerFlavor is lld, but lld did not exist - then _LinkerVersion is empty.

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@am11 am11 Apr 28, 2023 •
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Then it will result in error one way or the other with fuse-ld=<non-existing-flavor>. We shouldn't be checking for emptiness.

fuse-ld is even sensitive to version. Try apt install clang-13 lld-14 and fuse-ld=lld will fail.

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The problem is that if we try to compare versions against an empty string, the build fails at that comparison:

A numeric comparison was attempted on "$(_LinkerVersion)" that evaluates to "" instead of a number, in condition "'$(LinkerFlavor)' == 'lld' and '$(_LinkerVersion)' > '12'"

This looks like an error in the build logic, whereas failing on the invocation with:

clang : error : invalid linker name in argument '-fuse-ld=lld

gives a clearer indication of what's wrong.

IgnoreExitCode="true" IgnoreStandardErrorWarningFormat="true" StandardOutputImportance="Low" StandardErrorImportance="Low" ConsoleToMSBuild="true">
<Output TaskParameter="ExitCode" PropertyName="_LinkerVersionStringExitCode" />
<Output TaskParameter="ConsoleOutput" PropertyName="_LinkerVersionString" />
</Exec>

<PropertyGroup Condition="'$(LinkerFlavor)' == ''">
<LinkerFlavor Condition="'$(_LinkerVersionStringExitCode)' == '0'">lld</LinkerFlavor>
<LinkerFlavor Condition="'$(LinkerFlavor)' == '' and '$(_targetOS)' == 'linux'">bfd</LinkerFlavor>
</PropertyGroup>

<ItemGroup>
<LinkerArg Include="-fuse-ld=$(LinkerFlavor)" Condition="'$(LinkerFlavor)' != ''" />
</ItemGroup>

<PropertyGroup Condition="'$(_LinkerVersionStringExitCode)' == '0' and '$(_LinkerVersionString)' != ''">
<_LinkerVersion>$([System.Text.RegularExpressions.Regex]::Match($(_LinkerVersionString), '[1-9]\d*'))</_LinkerVersion>
</PropertyGroup>
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4 changes: 2 additions & 2 deletions src/coreclr/nativeaot/BuildIntegration/Microsoft.NETCore.Native.targets
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Same as above, revert changes in this file.

Original file line number Diff line number Diff line change
Expand Up @@ -321,7 +321,7 @@ The .NET Foundation licenses this file to you under the MIT license.
<ItemGroup Condition="'$(_targetOS)' != 'win' and '$(_IsApplePlatform)' != 'true'">
<CustomLinkerArg Include="-Wl,--discard-all" />
<CustomLinkerArg Include="-Wl,--gc-sections" Condition="'$(LinkerFlavor)' == '' or '$(LinkerFlavor)' == 'bfd' or '$(LinkerFlavor)' == 'lld'" />
<CustomLinkerArg Include="-Wl,-T,&quot;$(NativeIntermediateOutputPath)sections.ld&quot;" Condition="'$(LinkerFlavor)' == 'lld' and '$(_LinkerVersion)' &gt; '12'" />
<CustomLinkerArg Include="-Wl,-T,&quot;$(NativeIntermediateOutputPath)sections.ld&quot;" Condition="'$(LinkerFlavor)' == 'lld' and '$(_LinkerVersion)' != '' and '$(_LinkerVersion)' &gt; '12'" />
</ItemGroup>
<ItemGroup>
<CustomLibArg Include="-crs &quot;$(NativeBinary)&quot;" Condition="'$(_targetOS)' != 'win'" />
Expand All @@ -340,7 +340,7 @@ The .NET Foundation licenses this file to you under the MIT license.
</PropertyGroup>

<!-- write linker script for lld (13+) to retain the __modules section -->
<WriteLinesToFile File="$(NativeIntermediateOutputPath)sections.ld" Lines="OVERWRITE_SECTIONS { __modules : { KEEP(*(__modules)) } }" Overwrite="true" Condition="'$(LinkerFlavor)' == 'lld' and '$(_LinkerVersion)' &gt; '12'" />
<WriteLinesToFile File="$(NativeIntermediateOutputPath)sections.ld" Lines="OVERWRITE_SECTIONS { __modules : { KEEP(*(__modules)) } }" Overwrite="true" Condition="'$(LinkerFlavor)' == 'lld' and '$(_LinkerVersion)' != '' and '$(_LinkerVersion)' &gt; '12'" />

<Exec Command="&quot;$(CppLinker)&quot; @(CustomLinkerArg, ' ')" Condition="'$(_targetOS)' != 'win' and '$(NativeLib)' != 'Static'" IgnoreStandardErrorWarningFormat="$(_IgnoreLinkerWarnings)" />
<Exec Command="&quot;$(CppLibCreator)&quot; @(CustomLibArg, ' ')" Condition="'$(_targetOS)' != 'win' and '$(NativeLib)' == 'Static'" />
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5 changes: 0 additions & 5 deletions src/coreclr/tools/aot/crossgen2/crossgen2.csproj
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Expand Up @@ -88,11 +88,6 @@
<Target Name="LocateNativeCompiler"
Condition="'$(NativeAotSupported)' == 'true' and '$(_IsPublishing)' == 'true' and '$(HostOS)' != 'windows'"
BeforeTargets="SetupOSSpecificProps">
<PropertyGroup>
<CppCompilerAndLinker Condition="'$(CppCompilerAndLinker)' == ''">clang</CppCompilerAndLinker>
<LinkerFlavor Condition="'$(CppCompilerAndLinker)' == 'clang' and '$(TargetOS)' == 'linux'">lld</LinkerFlavor>
</PropertyGroup>

<Exec Command="sh -c 'build_arch=&quot;$(TargetArchitecture)&quot; compiler=&quot;$(CppCompilerAndLinker)&quot; . &quot;$(RepositoryEngineeringDir)/common/native/init-compiler.sh&quot; &amp;&amp; echo $CC' 2>/dev/null"
EchoOff="true"
ConsoleToMsBuild="true"
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1 change: 0 additions & 1 deletion src/tests/Directory.Build.targets
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Expand Up @@ -533,7 +533,6 @@
<IlcFrameworkNativePath>$(MicrosoftNetCoreAppRuntimePackNativeDir)</IlcFrameworkNativePath>
<RuntimeIdentifier>$(OutputRID)</RuntimeIdentifier>

<LinkerFlavor Condition="'$(TargetOS)' == 'linux'">lld</LinkerFlavor>
<SysRoot Condition="'$(CrossBuild)' == 'true' and '$(HostOS)' != 'windows'">$(ROOTFS_DIR)</SysRoot>
<BuildNativeAotFrameworkObjects Condition="'$(IlcMultiModule)' == 'true'">true</BuildNativeAotFrameworkObjects>
<DisableFrameworkLibGeneration Condition="'$(BuildNativeAotFrameworkObjects)' == 'true'">true</DisableFrameworkLibGeneration>
Expand Down