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Merge commit '475ff348f1e9' from llvm.org/release/21.x into stable/21.x
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‎clang/docs/ThinLTO.rst

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@@ -240,6 +240,38 @@ The ``BOOTSTRAP_LLVM_ENABLE_LTO=Thin`` will enable ThinLTO for stage 2 and
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stage 3 in case the compiler used for stage 1 does not support the ThinLTO
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option.
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Integrated Distributed ThinLTO (DTLTO)
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--------------------------------------
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Integrated Distributed ThinLTO (DTLTO) enables the distribution of backend
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ThinLTO compilations via external distribution systems, such as Incredibuild,
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during the traditional link step.
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The implementation is documented here: https://llvm.org/docs/DTLTO.html.
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DTLTO requires the LLD linker (``-fuse-ld=lld``).
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``-fthinlto-distributor=<path>``
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- Specifies the ``<path>`` to the distributor process executable for DTLTO.
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- If specified, ThinLTO backend compilations will be distributed by LLD.
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``-Xthinlto-distributor=<arg>``
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- Passes ``<arg>`` to the distributor process (see ``-fthinlto-distributor=``).
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- Can be specified multiple times to pass multiple options.
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- Multiple options can also be specified by separating them with commas.
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Examples:
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- ``clang -flto=thin -fthinlto-distributor=incredibuild.exe -Xthinlto-distributor=--verbose,--j10 -fuse-ld=lld``
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- ``clang -flto=thin -fthinlto-distributor=$(which python) -Xthinlto-distributor=incredibuild.py -fuse-ld=lld``
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If ``-fthinlto-distributor=`` is specified, Clang supplies the path to a
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compiler to be executed remotely to perform the ThinLTO backend
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compilations. Currently, this is Clang itself.
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Note that currently, DTLTO is only supported in some LLD flavors. Support can
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be added to other LLD flavours in the future.
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See `DTLTO <https://lld.llvm.org/dtlto.html>`_ for more information.
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More Information
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================
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‎clang/include/clang/Driver/Options.td

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@@ -1017,6 +1017,13 @@ def Xlinker : Separate<["-"], "Xlinker">, Flags<[LinkerInput, RenderAsInput]>,
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Visibility<[ClangOption, CLOption, FlangOption]>,
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HelpText<"Pass <arg> to the linker">, MetaVarName<"<arg>">,
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Group<Link_Group>;
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def Xthinlto_distributor_EQ : CommaJoined<["-"], "Xthinlto-distributor=">,
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Flags<[LinkOption]>,
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Visibility<[ClangOption, CLOption]>,
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HelpText<"Pass <arg> to the ThinLTO distributor process. Can be specified "
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"multiple times or with comma-separated values.">,
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MetaVarName<"<arg>">,
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Group<Link_Group>;
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def Xoffload_linker : JoinedAndSeparate<["-"], "Xoffload-linker">,
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Visibility<[ClangOption, FlangOption]>,
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HelpText<"Pass <arg> to the offload linkers or the ones identified by -<triple>">,
@@ -4375,7 +4382,12 @@ def ffinite_loops: Flag<["-"], "ffinite-loops">, Group<f_Group>,
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def fno_finite_loops: Flag<["-"], "fno-finite-loops">, Group<f_Group>,
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HelpText<"Do not assume that any loop is finite.">,
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Visibility<[ClangOption, CC1Option]>;
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def fthinlto_distributor_EQ : Joined<["-"], "fthinlto-distributor=">,
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Group<f_Group>,
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HelpText<"Path to the ThinLTO distributor process. If specified, "
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"ThinLTO backend compilations will be distributed by LLD">,
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MetaVarName<"<path>">,
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Visibility<[ClangOption, CLOption]>;
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def ftrigraphs : Flag<["-"], "ftrigraphs">, Group<f_Group>,
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HelpText<"Process trigraph sequences">, Visibility<[ClangOption, CC1Option]>;
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def fno_trigraphs : Flag<["-"], "fno-trigraphs">, Group<f_Group>,

‎clang/lib/Driver/ToolChains/CommonArgs.cpp

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@@ -1320,6 +1320,17 @@ void tools::addLTOOptions(const ToolChain &ToolChain, const ArgList &Args,
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if (Args.hasArg(options::OPT_ftime_report))
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CmdArgs.push_back(
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Args.MakeArgString(Twine(PluginOptPrefix) + "-time-passes"));
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if (Arg *A = Args.getLastArg(options::OPT_fthinlto_distributor_EQ)) {
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CmdArgs.push_back(
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Args.MakeArgString("--thinlto-distributor=" + Twine(A->getValue())));
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CmdArgs.push_back(
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Args.MakeArgString("--thinlto-remote-compiler=" +
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Twine(ToolChain.getDriver().getClangProgramPath())));
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for (auto A : Args.getAllArgValues(options::OPT_Xthinlto_distributor_EQ))
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CmdArgs.push_back(Args.MakeArgString("--thinlto-distributor-arg=" + A));
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}
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}
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void tools::addOpenMPRuntimeLibraryPath(const ToolChain &TC,

‎clang/test/Driver/DTLTO/dtlto.c

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// REQUIRES: lld
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/// Check DTLTO options are forwarded to the linker.
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/// Check that options are forwarded as expected with --thinlto-distributor=.
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// RUN: %clang -flto=thin %s -### -fuse-ld=lld --target=x86_64-linux-gnu \
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// RUN: -Xthinlto-distributor=a1 -Xthinlto-distributor=a2,a3 \
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// RUN: -fthinlto-distributor=d.exe -Werror 2>&1 | \
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// RUN: FileCheck %s --check-prefix=FORWARD
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// FORWARD: ld.lld
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// FORWARD-SAME: "--thinlto-distributor=d.exe"
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// FORWARD-SAME: "--thinlto-remote-compiler={{[^"]+}}"
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// FORWARD-SAME: "--thinlto-distributor-arg=a1"
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// FORWARD-SAME: "--thinlto-distributor-arg=a2"
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// FORWARD-SAME: "--thinlto-distributor-arg=a3"
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/// Check that options are not added without --thinlto-distributor= and
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/// that a warning is issued for unused -Xthinlto-distributor options.
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// RUN: %clang -flto=thin %s -### -fuse-ld=lld --target=x86_64-linux-gnu \
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// RUN: -Xthinlto-distributor=a1 -Xthinlto-distributor=a2,a3 2>&1 | \
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// RUN: FileCheck %s --check-prefix=NODIST --implicit-check-not=distributor \
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// RUN: --implicit-check-not=remote-compiler
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// NODIST: warning: argument unused during compilation: '-Xthinlto-distributor=a1'
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// NODIST: warning: argument unused during compilation: '-Xthinlto-distributor=a2,a3'
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// NODIST: ld.lld
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/// Check the expected arguments are forwarded by default with only
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/// --thinlto-distributor=.
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// RUN: %clang -flto=thin %s -### -fuse-ld=lld --target=x86_64-linux-gnu \
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// RUN: -fthinlto-distributor=d.exe -Werror 2>&1 | \
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// RUN: FileCheck %s --check-prefix=DEFAULT --implicit-check-not=distributor \
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// RUN: --implicit-check-not=remote-compiler
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// DEFAULT: ld.lld
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// DEFAULT-SAME: "--thinlto-distributor=d.exe"
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// DEFAULT-SAME: "--thinlto-remote-compiler={{.*}}clang{{[^\"]*}}"
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/// Check that nothing is forwarded when the compiler is not in LTO mode, and that
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/// appropriate unused option warnings are issued.
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// RUN: %clang %s -### -fuse-ld=lld --target=x86_64-linux-gnu \
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// RUN: -fthinlto-distributor=d.exe 2>&1 | \
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// RUN: FileCheck %s --check-prefix=NOFLTO --implicit-check-not=distributor \
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// RUN: --implicit-check-not=remote-compiler
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// NOFLTO: warning: argument unused during compilation: '-fthinlto-distributor=d.exe'
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// NOFLTO: ld.lld

‎cross-project-tests/dtlto/ld-dtlto.c

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@@ -5,13 +5,11 @@
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// RUN: rm -rf %t && mkdir %t && cd %t
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// RUN: %clang --target=x86_64-linux-gnu -c -flto=thin %s -o dtlto.o
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// RUN: ld.lld dtlto.o \
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// RUN: --thinlto-distributor=%python \
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// RUN: --thinlto-distributor-arg=%llvm_src_root/utils/dtlto/local.py \
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// RUN: --thinlto-remote-compiler=%clang \
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// RUN: --thinlto-remote-compiler-arg=--save-temps
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// RUN: %clang --target=x86_64-linux-gnu %s -flto=thin -fuse-ld=lld \
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// RUN: -fthinlto-distributor=%python \
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// RUN: -Xthinlto-distributor=%llvm_src_root/utils/dtlto/local.py \
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// RUN: -Wl,--thinlto-remote-compiler-arg=--save-temps \
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// RUN: -nostdlib -Werror
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/// Check that the required output files have been created.
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// RUN: ls | sort | FileCheck %s
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/// Linked ELF.
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// CHECK: {{^}}a.out{{$}}
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/// Produced by the bitcode compilation.
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// CHECK-NEXT: {{^}}dtlto.o{{$}}
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/// --save-temps output for the backend compilation.
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// CHECK-NEXT: {{^}}dtlto.s{{$}}
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// CHECK-NEXT: {{^}}dtlto.s.0.preopt.bc{{$}}
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// CHECK-NEXT: {{^}}dtlto.s.1.promote.bc{{$}}
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// CHECK-NEXT: {{^}}dtlto.s.2.internalize.bc{{$}}
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// CHECK-NEXT: {{^}}dtlto.s.3.import.bc{{$}}
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// CHECK-NEXT: {{^}}dtlto.s.4.opt.bc{{$}}
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// CHECK-NEXT: {{^}}dtlto.s.5.precodegen.bc{{$}}
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// CHECK-NEXT: {{^}}dtlto.s.resolution.txt{{$}}
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// CHECK-NEXT: {{^}}ld-dtlto-[[TMP:[a-zA-Z0-9_]+]].s{{$}}
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// CHECK-NEXT: {{^}}ld-dtlto-[[TMP]].s.0.preopt.bc{{$}}
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// CHECK-NEXT: {{^}}ld-dtlto-[[TMP]].s.1.promote.bc{{$}}
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// CHECK-NEXT: {{^}}ld-dtlto-[[TMP]].s.2.internalize.bc{{$}}
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// CHECK-NEXT: {{^}}ld-dtlto-[[TMP]].s.3.import.bc{{$}}
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// CHECK-NEXT: {{^}}ld-dtlto-[[TMP]].s.4.opt.bc{{$}}
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// CHECK-NEXT: {{^}}ld-dtlto-[[TMP]].s.5.precodegen.bc{{$}}
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// CHECK-NEXT: {{^}}ld-dtlto-[[TMP]].s.resolution.txt{{$}}
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/// No files are expected after.
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// CHECK-NOT: {{.}}

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