[PATCH] D31101: [ThinLTO] Use clang's existing code gen handling for ThinLTO backends

[Teresa Johnson via Phabricator via cfe-commits]

tejohnson updated this revision to Diff 92324.
tejohnson added a comment.

As discussed in the review threads for https://reviews.llvm.org/D31114 and https://reviews.llvm.org/D31100, only fall
back to clang's output file emission for -emit-llvm and -emit-llvm-bc.


https://reviews.llvm.org/D31101

Files:
  lib/CodeGen/BackendUtil.cpp
  test/CodeGen/thinlto-emit-llvm.c


Index: test/CodeGen/thinlto-emit-llvm.c
===================================================================
--- /dev/null
+++ test/CodeGen/thinlto-emit-llvm.c
@@ -0,0 +1,10 @@
+// Test to ensure -emit-llvm and -emit-llvm-bc work when invoking the
+// ThinLTO backend path.
+// RUN: %clang -O2 %s -flto=thin -c -o %t.o
+// RUN: llvm-lto -thinlto -o %t %t.o
+// RUN: %clang_cc1 -O2 -x ir %t.o -fthinlto-index=%t.thinlto.bc -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 -O2 -x ir %t.o -fthinlto-index=%t.thinlto.bc -emit-llvm-bc -o - | llvm-dis -o - | FileCheck %s
+
+// CHECK: define void @foo()
+void foo() {
+}
Index: lib/CodeGen/BackendUtil.cpp
===================================================================
--- lib/CodeGen/BackendUtil.cpp
+++ lib/CodeGen/BackendUtil.cpp
@@ -897,7 +897,8 @@
 
 static void runThinLTOBackend(ModuleSummaryIndex *CombinedIndex, Module *M,
                               std::unique_ptr<raw_pwrite_stream> OS,
-                              std::string SampleProfile) {
+                              std::string SampleProfile,
+                              bool SkipCodeGen) {
   StringMap<std::map<GlobalValue::GUID, GlobalValueSummary *>>
       ModuleToDefinedGVSummaries;
   CombinedIndex->collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
@@ -949,6 +950,7 @@
   };
   lto::Config Conf;
   Conf.SampleProfile = SampleProfile;
+  Conf.SkipCodeGen = SkipCodeGen;
   if (Error E = thinBackend(
           Conf, 0, AddStream, *M, *CombinedIndex, ImportList,
           ModuleToDefinedGVSummaries[M->getModuleIdentifier()], ModuleMap)) {
@@ -984,9 +986,16 @@
     // of an error).
     bool DoThinLTOBackend = CombinedIndex != nullptr;
     if (DoThinLTOBackend) {
-      runThinLTOBackend(CombinedIndex.get(), M, std::move(OS),
-                        CGOpts.SampleProfileFile);
-      return;
+      bool UsesCodeGen = (Action != Backend_EmitNothing &&
+                          Action != Backend_EmitBC &&
+                          Action != Backend_EmitLL);
+      if (UsesCodeGen) {
+        runThinLTOBackend(CombinedIndex.get(), M, std::move(OS),
+                          CGOpts.SampleProfileFile, /*SkipCodeGen*/false);
+        return;
+      } else
+        runThinLTOBackend(CombinedIndex.get(), M, nullptr,
+                          CGOpts.SampleProfileFile, /*SkipCodeGen*/true);
     }
   }
 


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