[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.

llvm-svn: 283787

3 files changed, 39 insertions, 1 deletions

diff --git a/lld/ELF/LTO.cpp b/lld/ELF/LTO.cpp
index 9c7de9d613d..ede80c24653 100644
--- a/lld/ELF/LTO.cpp
+++ b/lld/ELF/LTO.cpp
@@ -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> createLTO() {
     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);
 }
 
diff --git a/lld/test/ELF/lto/Inputs/thinlto.ll b/lld/test/ELF/lto/Inputs/thinlto.ll
new file mode 100644
index 00000000000..31c72ec4653
--- /dev/null
+++ b/lld/test/ELF/lto/Inputs/thinlto.ll
@@ -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
+}
diff --git a/lld/test/ELF/lto/thinlto.ll b/lld/test/ELF/lto/thinlto.ll
new file mode 100644
index 00000000000..98d4aff2f99
--- /dev/null
+++ b/lld/test/ELF/lto/thinlto.ll
@@ -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
+}