[LTO] Infer ELFKind/EMachine from Bitcode files

So that users are not forced to pass `-m` on the command line
when the inputs are all bitcode.

PR:   28268
Differential Revision:  http://reviews.llvm.org/D21779

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@274107 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 41 insertions, 2 deletions

diff --git a/ELF/InputFiles.cpp b/ELF/InputFiles.cpp
index 786604c8d..eb17d86a4 100644
--- a/ELF/InputFiles.cpp
+++ b/ELF/InputFiles.cpp
@@ -14,6 +14,7 @@
 #include "SymbolTable.h"
 #include "Symbols.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/Bitcode/ReaderWriter.h"
 #include "llvm/CodeGen/Analysis.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
@@ -552,7 +553,45 @@ template <class ELFT> void SharedFile<ELFT>::parseRest() {
   }
 }
 
-BitcodeFile::BitcodeFile(MemoryBufferRef M) : InputFile(BitcodeKind, M) {}
+static ELFKind getELFKind(MemoryBufferRef MB) {
+  std::string TripleStr = getBitcodeTargetTriple(MB, Driver->Context);
+  Triple TheTriple(TripleStr);
+  bool Is64Bits = TheTriple.isArch64Bit();
+  if (TheTriple.isLittleEndian())
+    return Is64Bits ? ELF64LEKind : ELF32LEKind;
+  return Is64Bits ? ELF64BEKind : ELF32BEKind;
+}
+
+static uint8_t getMachineKind(MemoryBufferRef MB) {
+  std::string TripleStr = getBitcodeTargetTriple(MB, Driver->Context);
+  switch (Triple(TripleStr).getArch()) {
+    case Triple::aarch64:
+      return EM_AARCH64;
+    case Triple::arm:
+      return EM_ARM;
+    case Triple::mips:
+    case Triple::mipsel:
+    case Triple::mips64:
+    case Triple::mips64el:
+      return EM_MIPS;
+    case Triple::ppc:
+      return EM_PPC;
+    case Triple::ppc64:
+      return EM_PPC64;
+    case Triple::x86:
+      return EM_386;
+    case Triple::x86_64:
+      return EM_X86_64;
+    default:
+      fatal("unsupported architecture: " + TripleStr);
+  }
+}
+
+BitcodeFile::BitcodeFile(MemoryBufferRef MB) :
+    InputFile(BitcodeKind, MB) {
+  EKind = getELFKind(MB);
+  EMachine = getMachineKind(MB);
+}
 
 static uint8_t getGvVisibility(const GlobalValue *GV) {
   switch (GV->getVisibility()) {
diff --git a/test/ELF/lto/pic.ll b/test/ELF/lto/pic.ll
index 0d61d6a62..abc514d7c 100644
--- a/test/ELF/lto/pic.ll
+++ b/test/ELF/lto/pic.ll
@@ -1,7 +1,7 @@
 ; REQUIRES: x86
 
 ; RUN: llvm-as %s -o %t.o
-; RUN: ld.lld %t.o -m elf_x86_64 -o %t.so -shared
+; RUN: ld.lld %t.o -o %t.so -shared
 ; RUN: llvm-readobj -r %t.so | FileCheck %s
 
 ; CHECK:      Relocations [