[mips] Add support to '.set mips64'.

The '.set mips64' directive enables the feature Mips:FeatureMips64
from assembly. Note that it doesn't modify the ELF header as opposed
to the use of -mips64 from the command-line. The reason for this
is that we want to be as compatible as possible with existing assemblers
like GAS.

llvm-svn: 204817
diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp b/llvm/lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
index f21dbed3..01730dd 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
+++ b/llvm/lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
@@ -105,6 +105,10 @@
   OS << "\t.set\tmips32r2\n";
 }
 
+void MipsTargetAsmStreamer::emitDirectiveSetMips64() {
+  OS << "\t.set\tmips64\n";
+}
+
 void MipsTargetAsmStreamer::emitDirectiveSetMips64R2() {
   OS << "\t.set\tmips64r2\n";
 }
@@ -359,6 +363,10 @@
   // No action required for ELF output.
 }
 
+void MipsTargetELFStreamer::emitDirectiveSetMips64() {
+  // No action required for ELF output.
+}
+
 void MipsTargetELFStreamer::emitDirectiveSetMips64R2() {
   // No action required for ELF output.
 }