[Triple] Make mipsel-*-windows-* use COFF files by default

Windows NT/MIPS and Windows CE/MIPS always used COFF format.

Author: hpoussin

llvm/lib/TargetParser/Triple.cpp

@@ -905,7 +905,6 @@ static Triple::ObjectFormatType getDefaultFormat(const Triple &T) {
   case Triple::mips64:
   case Triple::mips64el:
   case Triple::mips:
-  case Triple::mipsel:
   case Triple::msp430:
   case Triple::nvptx64:
   case Triple::nvptx:
@@ -930,6 +929,11 @@ static Triple::ObjectFormatType getDefaultFormat(const Triple &T) {
   case Triple::xtensa:
     return Triple::ELF;
 
+  case Triple::mipsel:
+    if (T.isOSWindows())
+      return Triple::COFF;
+    return Triple::ELF;
+
   case Triple::ppc64:
   case Triple::ppc:
     if (T.isOSAIX())

llvm/unittests/TargetParser/TripleTest.cpp

@@ -2302,6 +2302,10 @@ TEST(TripleTest, NormalizeWindows) {
             Triple::normalize("i686-pc-windows-elf-elf"));
 
   EXPECT_TRUE(Triple("x86_64-pc-win32").isWindowsMSVCEnvironment());
+
+  EXPECT_TRUE(Triple(Triple::normalize("mipsel-windows-msvccoff")).isOSBinFormatCOFF());
+  EXPECT_TRUE(Triple(Triple::normalize("mipsel-windows-msvc")).isOSBinFormatCOFF());
+  EXPECT_TRUE(Triple(Triple::normalize("mipsel-windows-gnu")).isOSBinFormatCOFF());
 }
 
 TEST(TripleTest, NormalizeAndroid) {