[CGData][ThinLTO] Global Outlining with Two-CodeGen Rounds (#90933)

This feature is enabled by `-codegen-data-thinlto-two-rounds`, which
effectively runs the `-codegen-data-generate` and `-codegen-data-use` in
two rounds to enable global outlining with ThinLTO.
1. The first round: Run both optimization + codegen with a scratch
output.
Before running codegen, we serialize the optimized bitcode modules to a
temporary path.
 2. From the scratch object files, we merge them into the codegen data.
3. The second round: Read the optimized bitcode modules and start the
codegen only this time.
Using the codegen data, the machine outliner effectively performs the
global outlining.
 
Depends on #90934, #110461 and  #110463.
This is a patch for
https://discourse.llvm.org/t/rfc-enhanced-machine-outliner-part-2-thinlto-nolto/78753.

1 files changed, 5 insertions, 4 deletions

diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index abc936f..f018130 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -1321,10 +1321,11 @@ static void runThinLTOBackend(
     Conf.CGFileType = getCodeGenFileType(Action);
     break;
   }
-  if (Error E = thinBackend(
-          Conf, -1, AddStream, *M, *CombinedIndex, ImportList,
-          ModuleToDefinedGVSummaries[M->getModuleIdentifier()],
-          /* ModuleMap */ nullptr, Conf.CodeGenOnly, CGOpts.CmdArgs)) {
+  if (Error E =
+          thinBackend(Conf, -1, AddStream, *M, *CombinedIndex, ImportList,
+                      ModuleToDefinedGVSummaries[M->getModuleIdentifier()],
+                      /*ModuleMap=*/nullptr, Conf.CodeGenOnly,
+                      /*IRAddStream=*/nullptr, CGOpts.CmdArgs)) {
     handleAllErrors(std::move(E), [&](ErrorInfoBase &EIB) {
       errs() << "Error running ThinLTO backend: " << EIB.message() << '\n';
     });