[mips] Support micromips attribute passed by front-end

This patch adds handling of the `micromips` and `nomicromips` attributes
passed by front-end. The patch depends on D33363.

Differential revision: https://reviews.llvm.org/D33364

llvm-svn: 303545
diff --git a/llvm/lib/Target/Mips/MipsTargetMachine.cpp b/llvm/lib/Target/Mips/MipsTargetMachine.cpp
index 9e5935c..092de21 100644
--- a/llvm/lib/Target/Mips/MipsTargetMachine.cpp
+++ b/llvm/lib/Target/Mips/MipsTargetMachine.cpp
@@ -154,6 +154,11 @@
   bool hasNoMips16Attr =
       !F.getFnAttribute("nomips16").hasAttribute(Attribute::None);
 
+  bool HasMicroMipsAttr =
+      !F.getFnAttribute("micromips").hasAttribute(Attribute::None);
+  bool HasNoMicroMipsAttr =
+      !F.getFnAttribute("nomicromips").hasAttribute(Attribute::None);
+
   // FIXME: This is related to the code below to reset the target options,
   // we need to know whether or not the soft float flag is set on the
   // function, so we can enable it as a subtarget feature.
@@ -165,6 +170,10 @@
     FS += FS.empty() ? "+mips16" : ",+mips16";
   else if (hasNoMips16Attr)
     FS += FS.empty() ? "-mips16" : ",-mips16";
+  if (HasMicroMipsAttr)
+    FS += FS.empty() ? "+micromips" : ",+micromips";
+  else if (HasNoMicroMipsAttr)
+    FS += FS.empty() ? "-micromips" : ",-micromips";
   if (softFloat)
     FS += FS.empty() ? "+soft-float" : ",+soft-float";