Support more than one LTO partition.

Author: bd1976bris

lld/test/ELF/dtlto/parallel.test

@@ -0,0 +1,62 @@
+# REQUIRES: x86
+
+## Test that DTLTO works with more than one LTO partition.
+
+# RUN: rm -rf %t.dir && split-file %s %t.dir && cd %t.dir
+
+# Compile bitcode.
+RUN: llvm-as -o full.bc full.ll
+RUN: opt -thinlto-bc thin1.ll -o thin1.bc
+RUN: opt -thinlto-bc thin2.ll -o thin2.bc
+
+# Generate mock native object files.
+RUN: llc thin1.ll --filetype=obj -o thin1.o --relocation-model=pic
+RUN: llc thin2.ll --filetype=obj -o thin2.o --relocation-model=pic
+
+# Link with 3 LTO partitions.
+RUN: ld.lld full.bc thin1.bc thin2.bc \ 
+RUN:   --thinlto-distributor=%python \
+RUN:   --thinlto-remote-opt-tool=dummy \
+RUN:   -mllvm=-thinlto-distributor-arg=%llvm_src_root/utils/dtlto/mock.py \
+RUN:   -mllvm=-thinlto-distributor-arg=thin1.o \
+RUN:   -mllvm=-thinlto-distributor-arg=thin2.o \
+RUN:   --save-temps \
+RUN:   --lto-partitions=3 
+
+# DTLTO temporary object files include the task number and a PID component. The
+# task number should incorporate the LTO partition number.
+RUN: ls | FileCheck %s
+CHECK: thin1.3.[[#]].native.o
+CHECK: thin2.4.[[#]].native.o
+
+#--- full.ll
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @foo() mustprogress {
+  call void @bar()
+  ret void
+}
+
+define void @bar() mustprogress {
+  call void @foo()
+  ret void
+}
+
+#--- thin1.ll
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @baz() {
+entry:
+  ret void
+}
+
+#--- thin2.ll
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @_start() {
+entry:
+  ret void
+}

llvm/include/llvm/LTO/LTO.h

@@ -225,7 +225,7 @@ class ThinBackendProc {
         BackendThreadPool(ThinLTOParallelism) {}
 
   virtual ~ThinBackendProc() = default;
-  virtual void setup(unsigned MaxTasks) {}
+  virtual void setup(unsigned MaxTasks, unsigned ReservedTasks) {}
   virtual Error start(
       unsigned Task, BitcodeModule BM,
       const FunctionImporter::ImportMapTy &ImportList,

llvm/lib/LTO/LTO.cpp

@@ -2062,7 +2062,8 @@ Error LTO::runThinLTO(AddStreamFn AddStream, AddBufferFn AddBuffer,
           ResolvedODR[Mod.first], ThinLTO.ModuleMap, ThinLTO.ModuleTriples);
     };
 
-    BackendProcess->setup(ModuleMap.size());
+    BackendProcess->setup(ModuleMap.size(),
+                          RegularLTO.ParallelCodeGenParallelismLevel);
 
     if (BackendProcess->getThreadCount() == 1 ||
         BackendProcess->isSensitiveToInputOrder()) {
@@ -2228,6 +2229,9 @@ class OutOfProcessThinBackend : public CGThinBackend {
   // A unique string to identify the current link.
   SmallString<8> UID;
 
+  // The first ReservedTasks entries in the task range are used for Full LTO.
+  unsigned ReservedTasks;
+
 public:
   OutOfProcessThinBackend(
       const Config &Conf, ModuleSummaryIndex &CombinedIndex,
@@ -2244,9 +2248,10 @@ class OutOfProcessThinBackend : public CGThinBackend {
         RemoteOptTool(RemoteOptTool), DistributorPath(Distributor),
         SaveTemps(SaveTemps) {}
 
-  virtual void setup(unsigned MaxTasks) override {
+  virtual void setup(unsigned MaxTasks, unsigned ReservedTasks) override {
     UID = itostr(sys::Process::getProcessId());
     Jobs.resize((size_t)MaxTasks);
+    this->ReservedTasks = ReservedTasks;
   }
 
   Error start(
@@ -2263,7 +2268,7 @@ class OutOfProcessThinBackend : public CGThinBackend {
     sys::path::append(ObjFilePath, sys::path::stem(ModulePath) + "." +
                                        itostr(Task) + "." + UID + ".native.o");
 
-    Job &J = Jobs[Task - 1]; /*Task 0 is reserved*/
+    Job &J = Jobs[Task - ReservedTasks];
     J = {Task,
          ModulePath,
          ModuleTriples[ModulePath],