[llvm] fe5599e - [llvm-ar] Use target triple to deduce archive kind for bitcode inputs

[Pirama Arumuga Nainar via llvm-commits]

Author: Pirama Arumuga Nainar
Date: 2020-03-20T13:19:44-07:00
New Revision: fe5599eac6a57ad5a354e3b6fec9e97332304bac

URL: https://github.com/llvm/llvm-project/commit/fe5599eac6a57ad5a354e3b6fec9e97332304bac
DIFF: https://github.com/llvm/llvm-project/commit/fe5599eac6a57ad5a354e3b6fec9e97332304bac.diff

LOG: [llvm-ar] Use target triple to deduce archive kind for bitcode inputs

Summary:
When using full LTO on cross-compile settings, instead of generating the
default archive kind of the host platform, we could deduce the archive
kind based on the target triple.

This specifically addresses https://github.com/android/ndk/issues/1209
by making it possible to drop llvm-ar in place of GNU ar without extra
flags.

Reviewers: compnerd, pcc, srhines, danalbert

Subscribers: hiraditya, MaskRay, steven_wu, dexonsmith, rupprecht, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D76461

Added: 
    llvm/test/tools/llvm-ar/lto-kind-from-triple.test

Modified: 
    llvm/tools/llvm-ar/llvm-ar.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/test/tools/llvm-ar/lto-kind-from-triple.test b/llvm/test/tools/llvm-ar/lto-kind-from-triple.test
new file mode 100644
index 000000000000..92b194c6abf1
--- /dev/null
+++ b/llvm/test/tools/llvm-ar/lto-kind-from-triple.test
@@ -0,0 +1,26 @@
+## Ensure that we generate a GNU style archive if the first input is a bitcode
+## file with a GNU target triple (absence of __.SYMDEF in the archive).
+
+# RUN: echo -e 'target triple = "x86_64-unknown-linux-gnu" \n define void @_Z3foov() { ret void }' > %t.gnu.ll
+# RUN: llvm-as -o %t.gnu.o %t.gnu.ll
+
+# RUN: rm -f %t.ar
+# RUN: llvm-ar crs %t.ar %t.gnu.o
+# RUN: not grep -q __.SYMDEF %t.ar
+
+## Ensure that we generate a MachO style archive if the first input is a
+## bitcode file with a MachO target triple (presence of __.SYMDEF in the
+## archive).
+
+# RUN: echo -e 'target triple = "x86_64-apple-macosx10.9" \n define void @_Z3foov() { ret void }' > %t.macho.ll
+# RUN: llvm-as -o %t.macho.o %t.macho.ll
+
+# RUN: rm -f %t.ar
+# RUN: llvm-ar crs %t.ar %t.macho.o
+# RUN: grep -q __.SYMDEF %t.ar
+
+## Verify that archive format is based on the first input's target triple.
+
+# RUN: rm -f %t.ar
+# RUN: llvm-ar crs %t.ar %t.gnu.o %t.macho.o
+# RUN: not grep -q __.SYMDEF %t.ar

diff  --git a/llvm/tools/llvm-ar/llvm-ar.cpp b/llvm/tools/llvm-ar/llvm-ar.cpp
index 4e5c0b408f77..652219568db1 100644
--- a/llvm/tools/llvm-ar/llvm-ar.cpp
+++ b/llvm/tools/llvm-ar/llvm-ar.cpp
@@ -14,11 +14,14 @@
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/ADT/Triple.h"
+#include "llvm/BinaryFormat/Magic.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/Object/Archive.h"
 #include "llvm/Object/ArchiveWriter.h"
+#include "llvm/Object/IRObjectFile.h"
 #include "llvm/Object/MachO.h"
 #include "llvm/Object/ObjectFile.h"
+#include "llvm/Object/SymbolicFile.h"
 #include "llvm/Support/Chrono.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ConvertUTF.h"
@@ -875,8 +878,9 @@ static object::Archive::Kind getDefaultForHost() {
 }
 
 static object::Archive::Kind getKindFromMember(const NewArchiveMember &Member) {
+  auto MemBufferRef = Member.Buf->getMemBufferRef();
   Expected<std::unique_ptr<object::ObjectFile>> OptionalObject =
-      object::ObjectFile::createObjectFile(Member.Buf->getMemBufferRef());
+      object::ObjectFile::createObjectFile(MemBufferRef);
 
   if (OptionalObject)
     return isa<object::MachOObjectFile>(**OptionalObject)
@@ -885,6 +889,23 @@ static object::Archive::Kind getKindFromMember(const NewArchiveMember &Member) {
 
   // squelch the error in case we had a non-object file
   consumeError(OptionalObject.takeError());
+
+  // If we're adding a bitcode file to the archive, detect the Archive kind
+  // based on the target triple.
+  LLVMContext Context;
+  if (identify_magic(MemBufferRef.getBuffer()) == file_magic::bitcode) {
+    if (auto ObjOrErr = object::SymbolicFile::createSymbolicFile(
+            MemBufferRef, file_magic::bitcode, &Context)) {
+      auto &IRObject = cast<object::IRObjectFile>(**ObjOrErr);
+      return Triple(IRObject.getTargetTriple()).isOSDarwin()
+                 ? object::Archive::K_DARWIN
+                 : object::Archive::K_GNU;
+    } else {
+      // Squelch the error in case this was not a SymbolicFile.
+      consumeError(ObjOrErr.takeError());
+    }
+  }
+
   return getDefaultForHost();
 }