Add a libLTO API to query a memory buffer and check if it contains ObjC categories

The linker supports a feature to force load an object from a static
archive if it defines an Objective-C category.
This API supports this feature by looking at every section in the
module to find if a category is defined in the module.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@275125 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 29 insertions, 0 deletions

diff --git a/tools/llvm-lto/llvm-lto.cpp b/tools/llvm-lto/llvm-lto.cpp
index f3c6c62d496..84dce23aee2 100644
--- a/tools/llvm-lto/llvm-lto.cpp
+++ b/tools/llvm-lto/llvm-lto.cpp
@@ -156,6 +156,10 @@ static cl::opt<bool> RestoreGlobalsLinkage(
     "restore-linkage", cl::init(false),
     cl::desc("Restore original linkage of globals prior to CodeGen"));
 
+static cl::opt<bool> CheckHasObjC(
+    "check-for-objc", cl::init(false),
+    cl::desc("Only check if the module has objective-C defined in it"));
+
 namespace {
 struct ModuleInfo {
   std::vector<bool> CanBeHidden;
@@ -714,6 +718,21 @@ int main(int argc, char **argv) {
     return 0;
   }
 
+  if (CheckHasObjC) {
+    for (auto &Filename : InputFilenames) {
+      ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
+          MemoryBuffer::getFile(Filename);
+      error(BufferOrErr, "error loading file '" + Filename + "'");
+      auto Buffer = std::move(BufferOrErr.get());
+      LLVMContext Ctx;
+      if (llvm::isBitcodeContainingObjCCategory(*Buffer, Ctx))
+        outs() << "Bitcode " << Filename << " contains ObjC\n";
+      else
+        outs() << "Bitcode " << Filename << " does not contain ObjC\n";
+    }
+    return 0;
+  }
+
   if (ThinLTOMode.getNumOccurrences()) {
     if (ThinLTOMode.getNumOccurrences() > 1)
       report_fatal_error("You can't specify more than one -thinlto-action");
diff --git a/tools/lto/lto.cpp b/tools/lto/lto.cpp
index e69f360b074..0c36c99c07f 100644
--- a/tools/lto/lto.cpp
+++ b/tools/lto/lto.cpp
@@ -14,6 +14,7 @@
 
 #include "llvm-c/lto.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/Bitcode/ReaderWriter.h"
 #include "llvm/CodeGen/CommandFlags.h"
 #include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/DiagnosticPrinter.h"
@@ -180,6 +181,14 @@ bool lto_module_is_object_file_for_target(const char* path,
   return LTOModule::isBitcodeForTarget(Buffer->get(), target_triplet_prefix);
 }
 
+bool lto_module_has_objc_category(const void *mem, size_t length) {
+  std::unique_ptr<MemoryBuffer> Buffer(LTOModule::makeBuffer(mem, length));
+  if (!Buffer)
+    return false;
+  LLVMContext Ctx;
+  return llvm::isBitcodeContainingObjCCategory(*Buffer, Ctx);
+}
+
 bool lto_module_is_object_file_in_memory(const void* mem, size_t length) {
   return LTOModule::isBitcodeFile(mem, length);
 }
diff --git a/tools/lto/lto.exports b/tools/lto/lto.exports
index 83a59437e81..74091c2641b 100644
--- a/tools/lto/lto.exports
+++ b/tools/lto/lto.exports
@@ -18,6 +18,7 @@ lto_module_is_object_file
 lto_module_is_object_file_for_target
 lto_module_is_object_file_in_memory
 lto_module_is_object_file_in_memory_for_target
+lto_module_has_objc_category
 lto_module_dispose
 lto_api_version
 lto_codegen_set_diagnostic_handler