commit 2dfd6210dcc3782d0f298b7bb996cc313d53c3a6
Author: dim <dim@FreeBSD.org>
Date:   Sun Sep 22 17:31:27 2019 +0000

    Pull in r372513 from upstream lld trunk (by Simon Atanasyan):
    
      [mips] Deduce MIPS specific ELF header flags from `emulation`
    
      In case of linking binary blobs which do not have any ELF headers, we
      can deduce MIPS ABI ELF header flags from an `emulation` option.
    
      Patch by Kyle Evans.
    
    Requested by:   kevans :)

Notes:
    svn path=/projects/clang900-import/; revision=352600

diff --git tools/lld/ELF/Arch/MipsArchTree.cpp tools/lld/ELF/Arch/MipsArchTree.cpp
index f64d03756457..20e07e1114eb 100644
--- tools/lld/ELF/Arch/MipsArchTree.cpp
+++ tools/lld/ELF/Arch/MipsArchTree.cpp
@@ -294,12 +294,30 @@ static uint32_t getArchFlags(ArrayRef<FileFlags> files) {
   return ret;
 }
 
+// If we don't have any input files, we'll have to rely on the information we
+// can derive from emulation information, since this at least gets us ABI.
+static uint32_t getFlagsFromEmulation() {
+  uint32_t ret = 0;
+
+  if (config->emulation.empty())
+    return 0;
+
+  if (config->ekind == ELF32BEKind || config->ekind == ELF32LEKind) {
+    if (config->mipsN32Abi)
+      ret |= EF_MIPS_ABI2;
+    else
+      ret |= EF_MIPS_ABI_O32;
+  }
+
+  return ret;
+}
+
 template <class ELFT> uint32_t elf::calcMipsEFlags() {
   std::vector<FileFlags> v;
   for (InputFile *f : objectFiles)
     v.push_back({f, cast<ObjFile<ELFT>>(f)->getObj().getHeader()->e_flags});
   if (v.empty())
-    return 0;
+    return getFlagsFromEmulation();
   checkFlags(v);
   return getMiscFlags(v) | getPicFlags(v) | getArchFlags(v);
 }