[ThinLTO] Option to invoke ThinLTO backend passes and importing

Summary:
Adds new option -fthinlto-index=<file> to invoke the LTO pipeline
along with function importing via clang using the supplied function
summary index file. This supports invoking the parallel ThinLTO
backend processes in a distributed build environment via clang.

Additionally, this causes the module linker to be invoked on the bitcode
file being compiled to perform any necessary promotion and renaming of
locals that are exported via the function summary index file.

Add a couple tests that confirm we get expected errors when we try to
use the new option on a file that isn't bitcode, or specify an invalid
index file. The tests also confirm that we trigger the expected function
import pass.

Depends on D15024

Reviewers: joker.eph, dexonsmith

Subscribers: joker.eph, davidxl, cfe-commits

Differential Revision: http://reviews.llvm.org/D15025

llvm-svn: 254927

2 files changed, 20 insertions, 0 deletions

diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 2015e3b821d..7025314c691 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -3419,6 +3419,13 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
       Args.AddLastArg(CmdArgs, options::OPT_flto, options::OPT_flto_EQ);
   }
 
+  if (const Arg *A = Args.getLastArg(options::OPT_fthinlto_index_EQ)) {
+    if (!types::isLLVMIR(Input.getType()))
+      D.Diag(diag::err_drv_argument_only_allowed_with) << A->getAsString(Args)
+                                                       << "-x ir";
+    Args.AddLastArg(CmdArgs, options::OPT_fthinlto_index_EQ);
+  }
+
   // We normally speed up the clang process a bit by skipping destructors at
   // exit, but when we're generating diagnostics we can rely on some of the
   // cleanup.
diff --git a/clang/lib/Driver/Types.cpp b/clang/lib/Driver/Types.cpp
index 2085b012429..c29ce9462a0 100644
--- a/clang/lib/Driver/Types.cpp
+++ b/clang/lib/Driver/Types.cpp
@@ -128,6 +128,19 @@ bool types::isCXX(ID Id) {
   }
 }
 
+bool types::isLLVMIR(ID Id) {
+  switch (Id) {
+  default:
+    return false;
+
+  case TY_LLVM_IR:
+  case TY_LLVM_BC:
+  case TY_LTO_IR:
+  case TY_LTO_BC:
+    return true;
+  }
+}
+
 bool types::isCuda(ID Id) {
   switch (Id) {
   default: