[ThinLTO]LTO]Legacy] Fix dependent libraries support by adding querying of the IRSymtab

Dependent libraries support for the legacy api was committed in a
broken state (see: https://reviews.llvm.org/D60274). This was missed
due to the painful nature of having to integrate the changes into a
linker in order to test. This change implements support for dependent
libraries in the legacy LTO api:

- I have removed the current api function, which returns a single
string, and   added functions to access each dependent library
specifier individually.

- To reduce the testing pain, I have made the api functions as thin as
possible to   maximize coverage from llvm-lto.

- When doing ThinLTO the system linker will load the modules lazily
when scanning   the input files. Unfortunately, when modules are
lazily loaded there is no access   to module level named metadata. To
fix this I have added api functions that allow   querying the IRSymtab
for the dependent libraries. I hope to expand the api in the   future
so that, eventually, all the information needed by a client linker
during   scan can be retrieved from the IRSymtab.

Differential Revision: https://reviews.llvm.org/D62935

llvm-svn: 363140

3 files changed, 62 insertions, 10 deletions

diff --git a/llvm/tools/llvm-lto/llvm-lto.cpp b/llvm/tools/llvm-lto/llvm-lto.cpp
index 9aabe0a4282..585207b2518 100644
--- a/llvm/tools/llvm-lto/llvm-lto.cpp
+++ b/llvm/tools/llvm-lto/llvm-lto.cpp
@@ -204,6 +204,10 @@ static cl::opt<bool> ListSymbolsOnly(
     "list-symbols-only", cl::init(false),
     cl::desc("Instead of running LTO, list the symbols in each IR file"));
 
+static cl::opt<bool> ListDependentLibrariesOnly(
+    "list-dependent-libraries-only", cl::init(false),
+    cl::desc("Instead of running LTO, list the dependent libraries in each IR file"));
+
 static cl::opt<bool> SetMergedModule(
     "set-merged-module", cl::init(false),
     cl::desc("Use the first input module as the merged module"));
@@ -372,6 +376,34 @@ static void listSymbols(const TargetOptions &Options) {
   }
 }
 
+static std::unique_ptr<MemoryBuffer> loadFile(StringRef Filename) {
+    ExitOnError ExitOnErr("llvm-lto: error loading file '" + Filename.str() +
+        "': ");
+    return ExitOnErr(errorOrToExpected(MemoryBuffer::getFileOrSTDIN(Filename)));
+}
+
+static void listDependentLibraries() {
+  for (auto &Filename : InputFilenames) {
+    auto Buffer = loadFile(Filename);
+    std::string E;
+    std::unique_ptr<lto::InputFile> Input(LTOModule::createInputFile(
+        Buffer->getBufferStart(), Buffer->getBufferSize(), Filename.c_str(),
+        E));
+    if (!Input)
+      error(E);
+
+    // List the dependent libraries.
+    outs() << Filename << ":\n";
+    for (size_t I = 0, C = LTOModule::getDependentLibraryCount(Input.get());
+         I != C; ++I) {
+      size_t L = 0;
+      const char *S = LTOModule::getDependentLibrary(Input.get(), I, &L);
+      assert(S);
+      outs() << StringRef(S, L) << "\n";
+    }
+  }
+}
+
 /// Create a combined index file from the input IR files and write it.
 ///
 /// This is meant to enable testing of ThinLTO combined index generation,
@@ -449,12 +481,6 @@ std::unique_ptr<ModuleSummaryIndex> loadCombinedIndex() {
   return ExitOnErr(getModuleSummaryIndexForFile(ThinLTOIndex));
 }
 
-static std::unique_ptr<MemoryBuffer> loadFile(StringRef Filename) {
-  ExitOnError ExitOnErr("llvm-lto: error loading file '" + Filename.str() +
-                        "': ");
-  return ExitOnErr(errorOrToExpected(MemoryBuffer::getFileOrSTDIN(Filename)));
-}
-
 static std::unique_ptr<lto::InputFile> loadInputFile(MemoryBufferRef Buffer) {
   ExitOnError ExitOnErr("llvm-lto: error loading input '" +
                         Buffer.getBufferIdentifier().str() + "': ");
@@ -854,6 +880,11 @@ int main(int argc, char **argv) {
     return 0;
   }
 
+  if (ListDependentLibrariesOnly) {
+    listDependentLibraries();
+    return 0;
+  }
+
   if (IndexStats) {
     printIndexStats();
     return 0;
diff --git a/llvm/tools/lto/lto.cpp b/llvm/tools/lto/lto.cpp
index 01dc141ffd0..fc2d3da43c0 100644
--- a/llvm/tools/lto/lto.cpp
+++ b/llvm/tools/lto/lto.cpp
@@ -18,6 +18,7 @@
 #include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/DiagnosticPrinter.h"
 #include "llvm/IR/LLVMContext.h"
+#include "llvm/LTO/LTO.h"
 #include "llvm/LTO/legacy/LTOCodeGenerator.h"
 #include "llvm/LTO/legacy/LTOModule.h"
 #include "llvm/LTO/legacy/ThinLTOCodeGenerator.h"
@@ -325,10 +326,6 @@ const char* lto_module_get_linkeropts(lto_module_t mod) {
   return unwrap(mod)->getLinkerOpts().data();
 }
 
-const char* lto_module_get_dependent_libraries(lto_module_t mod) {
-    return unwrap(mod)->getDependentLibraries().data();
-}
-
 void lto_codegen_set_diagnostic_handler(lto_code_gen_t cg,
                                         lto_diagnostic_handler_t diag_handler,
                                         void *ctxt) {
@@ -635,3 +632,23 @@ lto_bool_t thinlto_codegen_set_pic_model(thinlto_code_gen_t cg,
   sLastErrorString = "Unknown PIC model";
   return true;
 }
+
+DEFINE_SIMPLE_CONVERSION_FUNCTIONS(lto::InputFile, lto_input_t)
+
+lto_input_t lto_input_create(const void *buffer, size_t buffer_size, const char *path) {
+  return wrap(LTOModule::createInputFile(buffer, buffer_size, path, sLastErrorString));
+}
+
+void lto_input_dispose(lto_input_t input) {
+  delete unwrap(input);
+}
+
+extern unsigned lto_input_get_num_dependent_libraries(lto_input_t input) {
+  return LTOModule::getDependentLibraryCount(unwrap(input));
+}
+
+extern const char *lto_input_get_dependent_library(lto_input_t input,
+                                                   size_t index,
+                                                   size_t *size) {
+  return LTOModule::getDependentLibrary(unwrap(input), index, size);
+}
diff --git a/llvm/tools/lto/lto.exports b/llvm/tools/lto/lto.exports
index cb881d104fb..34922c820d6 100644
--- a/llvm/tools/lto/lto.exports
+++ b/llvm/tools/lto/lto.exports
@@ -72,3 +72,7 @@ thinlto_codegen_disable_codegen
 thinlto_module_get_num_object_files
 thinlto_module_get_object_file
 thinlto_set_generated_objects_dir
+lto_input_create
+lto_input_destroy
+lto_input_get_num_dependent_libraries
+lto_input_get_dependent_library