Index: lib/Target/Mips/AsmParser/MipsAsmParser.cpp
===================================================================
--- lib/Target/Mips/AsmParser/MipsAsmParser.cpp
+++ lib/Target/Mips/AsmParser/MipsAsmParser.cpp
@@ -1900,6 +1900,11 @@
     return true;
   }
 
+  // We know we emitted an instruction on the MER_NotAMacro or MER_Success path.
+  // If we're in microMIPS mode then we must also set EF_MIPS_MICROMIPS.
+  if (inMicroMipsMode())
+    TOut.setUsesMicroMips();
+
   // If this instruction has a delay slot and .set reorder is active,
   // emit a NOP after it.
   if (FillDelaySlot) {
@@ -5289,6 +5294,7 @@
     getTargetStreamer().emitDirectiveSetDsp();
     break;
   case Mips::FeatureMicroMips:
+    setFeatureBits(Mips::FeatureMicroMips, "micromips");
     getTargetStreamer().emitDirectiveSetMicroMips();
     break;
   case Mips::FeatureMips1:
@@ -5587,6 +5593,7 @@
   } else if (Tok.getString() == "nomips16") {
     return parseSetNoMips16Directive();
   } else if (Tok.getString() == "nomicromips") {
+    clearFeatureBits(Mips::FeatureMicroMips, "micromips");
     getTargetStreamer().emitDirectiveSetNoMicroMips();
     Parser.eatToEndOfStatement();
     return false;
Index: lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
===================================================================
--- lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
+++ lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
@@ -40,6 +40,7 @@
 }
 void MipsTargetStreamer::emitDirectiveSetMicroMips() {}
 void MipsTargetStreamer::emitDirectiveSetNoMicroMips() {}
+void MipsTargetStreamer::setUsesMicroMips() {}
 void MipsTargetStreamer::emitDirectiveSetMips16() {}
 void MipsTargetStreamer::emitDirectiveSetNoMips16() { forbidModuleDirective(); }
 void MipsTargetStreamer::emitDirectiveSetReorder() { forbidModuleDirective(); }
@@ -830,11 +831,6 @@
 
 void MipsTargetELFStreamer::emitDirectiveSetMicroMips() {
   MicroMipsEnabled = true;
-
-  MCAssembler &MCA = getStreamer().getAssembler();
-  unsigned Flags = MCA.getELFHeaderEFlags();
-  Flags |= ELF::EF_MIPS_MICROMIPS;
-  MCA.setELFHeaderEFlags(Flags);
   forbidModuleDirective();
 }
 
@@ -843,6 +839,13 @@
   forbidModuleDirective();
 }
 
+void MipsTargetELFStreamer::setUsesMicroMips() {
+  MCAssembler &MCA = getStreamer().getAssembler();
+  unsigned Flags = MCA.getELFHeaderEFlags();
+  Flags |= ELF::EF_MIPS_MICROMIPS;
+  MCA.setELFHeaderEFlags(Flags);
+}
+
 void MipsTargetELFStreamer::emitDirectiveSetMips16() {
   MCAssembler &MCA = getStreamer().getAssembler();
   unsigned Flags = MCA.getELFHeaderEFlags();
Index: lib/Target/Mips/MipsTargetStreamer.h
===================================================================
--- lib/Target/Mips/MipsTargetStreamer.h
+++ lib/Target/Mips/MipsTargetStreamer.h
@@ -30,6 +30,7 @@
 
   virtual void emitDirectiveSetMicroMips();
   virtual void emitDirectiveSetNoMicroMips();
+  virtual void setUsesMicroMips();
   virtual void emitDirectiveSetMips16();
   virtual void emitDirectiveSetNoMips16();
 
@@ -290,6 +291,7 @@
 
   void emitDirectiveSetMicroMips() override;
   void emitDirectiveSetNoMicroMips() override;
+  void setUsesMicroMips() override;
   void emitDirectiveSetMips16() override;
 
   void emitDirectiveSetNoReorder() override;
Index: test/MC/Mips/elf_eflags_micromips.s
===================================================================
--- test/MC/Mips/elf_eflags_micromips.s
+++ test/MC/Mips/elf_eflags_micromips.s
@@ -1,7 +1,12 @@
-# RUN: llvm-mc -filetype=obj -triple mipsel-unknown-linux -mcpu=mips32 %s -o -| llvm-readobj -h | FileCheck %s
+# RUN: llvm-mc -filetype=obj -triple mipsel-unknown-linux -mcpu=mips32 \
+# RUN:     -mattr=+micromips < /dev/null -o -| llvm-readobj -h | FileCheck \
+# RUN:     -check-prefix=NO-MM %s
+# RUN: llvm-mc -filetype=obj -triple mipsel-unknown-linux -mcpu=mips32 %s -o - \
+# RUN:     | llvm-readobj -h | FileCheck %s
 
 # This *MUST* match the output of 'gcc -c' compiled with the same triple.
 # CHECK: Flags [ (0x52001004)
+# NO-MM: Flags [ (0x50001004)
 
         .set micromips
 f:
Index: test/MC/Mips/elf_eflags_micromips2.s
===================================================================
--- /dev/null
+++ test/MC/Mips/elf_eflags_micromips2.s
@@ -0,0 +1,11 @@
+# RUN: llvm-mc -filetype=obj -triple mipsel-unknown-linux -mcpu=mips32 %s -o - \
+# RUN:     | llvm-readobj -h | FileCheck %s
+
+# This *MUST* match the output of 'gcc -c' compiled with the same triple.
+# The microMIPS flag is not set if no microMIPS code was emitted.
+# CHECK: Flags [ (0x50001004)
+
+        nop
+        .set micromips
+        .set nomicromips
+        nop