Index: lib/MC/MCObjectFileInfo.cpp
===================================================================
--- lib/MC/MCObjectFileInfo.cpp
+++ lib/MC/MCObjectFileInfo.cpp
@@ -595,7 +595,18 @@
                        COFF::IMAGE_SCN_MEM_READ | COFF::IMAGE_SCN_MEM_WRITE,
       SectionKind::getData());
 
-  bool IsWoA = T.getArch() == Triple::arm || T.getArch() == Triple::thumb;
+  // If we are under Windows and compiling for thumb, we need to add an extra
+  // flag to the .text section to inform the linker thumb code is present! (see
+  // below).
+  // The flag is IMAGE_SCN_MEM_16BIT, which is documented by Microsoft as
+  // "reserved for future use" (see
+  // https://msdn.microsoft.com/en-us/library/windows/hardware/gg463119.aspx),
+  // but the dumpbin.exe tool from Visual Studio confirms that this set the
+  // corresponding "thumb code" flag on a section.
+  // Without this flag, the linker will interpret the code inside this section
+  // as ARM code, and will fail at lots of things (starting by the
+  // relocations).
+  const bool IsThumb = T.getArch() == Triple::thumb;
 
   CommDirectiveSupportsAlignment = true;
 
@@ -606,7 +617,7 @@
       SectionKind::getBSS());
   TextSection = Ctx->getCOFFSection(
       ".text",
-      (IsWoA ? COFF::IMAGE_SCN_MEM_16BIT : (COFF::SectionCharacteristics)0) |
+      (IsThumb ? COFF::IMAGE_SCN_MEM_16BIT : (COFF::SectionCharacteristics)0) |
           COFF::IMAGE_SCN_CNT_CODE | COFF::IMAGE_SCN_MEM_EXECUTE |
           COFF::IMAGE_SCN_MEM_READ,
       SectionKind::getText());