ELF: Add ThinLTO caching support.

This patch adds an option named --thinlto-cache-dir, which specifies the
path to a directory in which to cache native object files for ThinLTO
incremental builds.

Differential Revision: https://reviews.llvm.org/D30509

llvm-svn: 296702

7 files changed, 54 insertions, 5 deletions

diff --git a/lld/ELF/Config.h b/lld/ELF/Config.h
index a47d7cda4af..91d4eb7afc0 100644
--- a/lld/ELF/Config.h
+++ b/lld/ELF/Config.h
@@ -86,6 +86,7 @@ struct Configuration {
   llvm::StringRef OptRemarksFilename;
   llvm::StringRef SoName;
   llvm::StringRef Sysroot;
+  llvm::StringRef ThinLTOCacheDir;
   std::string RPath;
   std::vector<VersionDefinition> VersionDefinitions;
   std::vector<llvm::StringRef> AuxiliaryList;
diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
index 72bb10984ef..97fd5308321 100644
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -583,6 +583,7 @@ void LinkerDriver::readConfigs(opt::InputArgList &Args) {
   Config->Sysroot = getString(Args, OPT_sysroot);
   Config->Target1Rel = getArg(Args, OPT_target1_rel, OPT_target1_abs, false);
   Config->Target2 = getTarget2(Args);
+  Config->ThinLTOCacheDir = getString(Args, OPT_thinlto_cache_dir);
   Config->ThinLTOJobs = getInteger(Args, OPT_thinlto_jobs, -1u);
   Config->Threads = getArg(Args, OPT_threads, OPT_no_threads, true);
   Config->Trace = Args.hasArg(OPT_trace);
diff --git a/lld/ELF/LTO.cpp b/lld/ELF/LTO.cpp
index eec62e96bb1..9e271a2c6ed 100644
--- a/lld/ELF/LTO.cpp
+++ b/lld/ELF/LTO.cpp
@@ -18,6 +18,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/IR/DiagnosticPrinter.h"
+#include "llvm/LTO/Caching.h"
 #include "llvm/LTO/Config.h"
 #include "llvm/LTO/LTO.h"
 #include "llvm/Object/SymbolicFile.h"
@@ -142,11 +143,24 @@ std::vector<InputFile *> BitcodeCompiler::compile() {
   std::vector<InputFile *> Ret;
   unsigned MaxTasks = LTOObj->getMaxTasks();
   Buff.resize(MaxTasks);
-
-  checkError(LTOObj->run([&](size_t Task) {
-    return llvm::make_unique<lto::NativeObjectStream>(
-        llvm::make_unique<raw_svector_ostream>(Buff[Task]));
-  }));
+  Files.resize(MaxTasks);
+
+  // The --thinlto-cache-dir option specifies the path to a directory in which
+  // to cache native object files for ThinLTO incremental builds. If a path was
+  // specified, configure LTO to use it as the cache directory.
+  lto::NativeObjectCache Cache;
+  if (!Config->ThinLTOCacheDir.empty())
+    Cache = lto::localCache(Config->ThinLTOCacheDir,
+                            [&](size_t Task, StringRef Path) {
+                              Files[Task] = check(MemoryBuffer::getFile(Path));
+                            });
+
+  checkError(LTOObj->run(
+      [&](size_t Task) {
+        return llvm::make_unique<lto::NativeObjectStream>(
+            llvm::make_unique<raw_svector_ostream>(Buff[Task]));
+      },
+      Cache));
 
   for (unsigned I = 0; I != MaxTasks; ++I) {
     if (Buff[I].empty())
@@ -160,5 +174,10 @@ std::vector<InputFile *> BitcodeCompiler::compile() {
     InputFile *Obj = createObjectFile(MemoryBufferRef(Buff[I], "lto.tmp"));
     Ret.push_back(Obj);
   }
+
+  for (std::unique_ptr<MemoryBuffer> &File : Files)
+    if (File)
+      Ret.push_back(createObjectFile(*File));
+
   return Ret;
 }
diff --git a/lld/ELF/LTO.h b/lld/ELF/LTO.h
index b3d734f2d38..28afa0e83ad 100644
--- a/lld/ELF/LTO.h
+++ b/lld/ELF/LTO.h
@@ -49,6 +49,7 @@ public:
 private:
   std::unique_ptr<llvm::lto::LTO> LTOObj;
   std::vector<SmallString<0>> Buff;
+  std::vector<std::unique_ptr<MemoryBuffer>> Files;
 };
 }
 }
diff --git a/lld/ELF/Options.td b/lld/ELF/Options.td
index 508ab320533..c49306dd1fc 100644
--- a/lld/ELF/Options.td
+++ b/lld/ELF/Options.td
@@ -392,4 +392,6 @@ def opt_remarks_filename: S<"opt-remarks-filename">,
 def opt_remarks_with_hotness: F<"opt-remarks-with-hotness">,
   HelpText<"Include hotness informations in the optimization remarks file">;
 def save_temps: F<"save-temps">;
+def thinlto_cache_dir: J<"thinlto-cache-dir=">,
+  HelpText<"Path to ThinLTO cached object file directory">;
 def thinlto_jobs: J<"thinlto-jobs=">, HelpText<"Number of ThinLTO jobs">;
diff --git a/lld/test/ELF/lto/Inputs/cache.ll b/lld/test/ELF/lto/Inputs/cache.ll
new file mode 100644
index 00000000000..4abbb457137
--- /dev/null
+++ b/lld/test/ELF/lto/Inputs/cache.ll
@@ -0,0 +1,10 @@
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define i32 @main() {
+entry:
+  call void (...) @globalfunc()
+  ret i32 0
+}
+
+declare void @globalfunc(...)
diff --git a/lld/test/ELF/lto/cache.ll b/lld/test/ELF/lto/cache.ll
new file mode 100644
index 00000000000..74b1d197f19
--- /dev/null
+++ b/lld/test/ELF/lto/cache.ll
@@ -0,0 +1,15 @@
+; RUN: opt -module-hash -module-summary %s -o %t.o
+; RUN: opt -module-hash -module-summary %p/Inputs/cache.ll -o %t2.o
+
+; RUN: rm -Rf %t.cache && mkdir %t.cache
+; RUN: ld.lld --thinlto-cache-dir=%t.cache -o %t3.o %t2.o %t.o
+
+; RUN: ls %t.cache | count 2
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @globalfunc() #0 {
+entry:
+  ret void
+}