[lld] r283787 - [LTO/Thin] Make the number of threads to run in the BE configurable.

[Peter Collingbourne via llvm-commits]

We should expose this flag separately from the parallel LTO parallelism
level. See what we do in the gold plugin for example.

Peter

On Mon, Oct 10, 2016 at 11:12 AM, Davide Italiano via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: davide
> Date: Mon Oct 10 13:12:53 2016
> New Revision: 283787
>
> URL: http://llvm.org/viewvc/llvm-project?rev=283787&view=rev
> Log:
> [LTO/Thin] Make the number of threads to run in the BE configurable.
>
> Before the default was whatever number hardware_concurrency() returned.
> Users can specify the number of threads via --lto-jobs=X option.
>
> Added:
>     lld/trunk/test/ELF/lto/Inputs/thinlto.ll
>     lld/trunk/test/ELF/lto/thinlto.ll
> Modified:
>     lld/trunk/ELF/LTO.cpp
>
> Modified: lld/trunk/ELF/LTO.cpp
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/LTO.cpp?
> rev=283787&r1=283786&r2=283787&view=diff
> ============================================================
> ==================
> --- lld/trunk/ELF/LTO.cpp (original)
> +++ lld/trunk/ELF/LTO.cpp Mon Oct 10 13:12:53 2016
> @@ -49,7 +49,6 @@ static void checkError(Error E) {
>
>  static std::unique_ptr<lto::LTO> createLTO() {
>    lto::Config Conf;
> -  lto::ThinBackend Backend;
>
>    // LLD supports the new relocations.
>    Conf.Options = InitTargetOptionsFromCodeGenFlags();
> @@ -68,6 +67,9 @@ static std::unique_ptr<lto::LTO> createL
>      checkError(Conf.addSaveTemps(std::string(Config->OutputFile) + ".",
>                              /*UseInputModulePath*/ true));
>
> +  lto::ThinBackend Backend;
> +  if (Config->LtoJobs)
> +    Backend = lto::createInProcessThinBackend(Config->LtoJobs);
>    return llvm::make_unique<lto::LTO>(std::move(Conf), Backend,
> Config->LtoJobs);
>  }
>
>
> Added: lld/trunk/test/ELF/lto/Inputs/thinlto.ll
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/
> lto/Inputs/thinlto.ll?rev=283787&view=auto
> ============================================================
> ==================
> --- lld/trunk/test/ELF/lto/Inputs/thinlto.ll (added)
> +++ lld/trunk/test/ELF/lto/Inputs/thinlto.ll Mon Oct 10 13:12:53 2016
> @@ -0,0 +1,7 @@
> +target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
> +target triple = "x86_64-unknown-linux-gnu"
> +
> +define void @g() {
> +entry:
> +  ret void
> +}
>
> Added: lld/trunk/test/ELF/lto/thinlto.ll
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/
> lto/thinlto.ll?rev=283787&view=auto
> ============================================================
> ==================
> --- lld/trunk/test/ELF/lto/thinlto.ll (added)
> +++ lld/trunk/test/ELF/lto/thinlto.ll Mon Oct 10 13:12:53 2016
> @@ -0,0 +1,29 @@
> +; Basic ThinLTO tests.
> +; RUN: llvm-as %s -o %t.o
> +; RUN: llvm-as %p/Inputs/thinlto.ll -o %t2.o
> +
> +; First force single-threaded mode
> +; RUN: ld.lld -save-temps --lto-jobs=1 -shared %t.o %t2.o -o %t
> +; RUN: llvm-nm %t.lto.o | FileCheck %s --check-prefix=NM
> +
> +; NM: T f
> +; NM: T g
> +
> +; Next force multi-threaded mode
> +; RUN: ld.lld -save-temps --lto-jobs=2 -shared %t.o %t2.o -o %t2
> +; RUN: llvm-nm %t20.lto.o | FileCheck %s --check-prefix=NM1
> +; RUN: llvm-nm %t21.lto.o | FileCheck %s --check-prefix=NM2
> +
> +; NM1: T g
> +; NM2: T f
> +
> +target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
> +target triple = "x86_64-unknown-linux-gnu"
> +
> +declare void @g(...)
> +
> +define void @f() {
> +entry:
> +  call void (...) @g()
> +  ret void
> +}
>
>
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-- 
-- 
Peter
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