Index: lib/Target/Mips/AsmParser/MipsAsmParser.cpp
===================================================================
--- lib/Target/Mips/AsmParser/MipsAsmParser.cpp
+++ lib/Target/Mips/AsmParser/MipsAsmParser.cpp
@@ -26,6 +26,7 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/TargetRegistry.h"
+#include <stack>
 
 using namespace llvm;
 
@@ -40,6 +41,13 @@
 public:
   MipsAssemblerOptions() : aTReg(1), reorder(true), macro(true) {}
 
+  MipsAssemblerOptions(MipsAssemblerOptions *Opts) {
+    aTReg = Opts->getATRegNum();
+    reorder = Opts->isReorder();
+    macro = Opts->isMacro();
+    CurrentFeatures = Opts->getCurrentFeatures();
+  }
+
   unsigned getATRegNum() { return aTReg; }
   bool setATReg(unsigned Reg);
 
@@ -65,11 +73,25 @@
       Mips::FeatureMips64r6 | Mips::FeatureCnMips | Mips::FeatureFP64Bit |
       Mips::FeatureGP64Bit | Mips::FeatureNaN2008;
 
+  unsigned getCurrentFeatures() { return CurrentFeatures; }
+
+  void setCurrentFeatures(unsigned Features) { CurrentFeatures = Features; }
+
+  static unsigned getInitialFeatures() { return InitialFeatures; }
+  
+  static void setInitialFeatures(unsigned Features) { 
+    InitialFeatures = Features; 
+  }
+
 private:
   unsigned aTReg;
   bool reorder;
   bool macro;
+  unsigned CurrentFeatures;
+  static unsigned InitialFeatures;
 };
+
+unsigned MipsAssemblerOptions::InitialFeatures;
 }
 
 namespace {
@@ -81,7 +103,7 @@
 
   MCSubtargetInfo &STI;
   MCAsmParser &Parser;
-  MipsAssemblerOptions Options;
+  std::stack<MipsAssemblerOptions *> AssemblerOptions;
 
 #define GET_ASSEMBLER_HEADER
 #include "MipsGenAsmMatcher.inc"
@@ -171,6 +193,8 @@
   bool parseSetNoReorderDirective();
   bool parseSetNoMips16Directive();
   bool parseSetFpDirective();
+  bool parseSetPopDirective();
+  bool parseSetPushDirective();
 
   bool parseSetAssignment();
 
@@ -242,6 +266,8 @@
     STI.setFeatureBits(FeatureBits);
     setAvailableFeatures(
         ComputeAvailableFeatures(STI.ToggleFeature(ArchFeature)));
+
+    AssemblerOptions.top()->setCurrentFeatures(getAvailableFeatures());
   }
 
   void setFeatureBits(unsigned Feature, StringRef FeatureString) {
@@ -249,6 +275,7 @@
       setAvailableFeatures(
           ComputeAvailableFeatures(STI.ToggleFeature(FeatureString)));
     }
+    AssemblerOptions.top()->setCurrentFeatures(getAvailableFeatures());
   }
 
   void clearFeatureBits(unsigned Feature, StringRef FeatureString) {
@@ -256,6 +283,7 @@
       setAvailableFeatures(
           ComputeAvailableFeatures(STI.ToggleFeature(FeatureString)));
     }
+    AssemblerOptions.top()->setCurrentFeatures(getAvailableFeatures());
   }
 
 public:
@@ -273,6 +301,15 @@
     // Initialize the set of available features.
     setAvailableFeatures(ComputeAvailableFeatures(STI.getFeatureBits()));
 
+    AssemblerOptions.push(new MipsAssemblerOptions());   
+    
+    // Set the initial configuration given through the command-line or by using
+    // the default values.
+    AssemblerOptions.top()->setCurrentFeatures(getAvailableFeatures());
+
+    // We cache the initial configuration here so that it's always retrievable.    
+    AssemblerOptions.top()->setInitialFeatures(getAvailableFeatures());
+
     getTargetStreamer().updateABIInfo(*this);
 
     // Assert exactly one ABI was chosen.
@@ -1005,7 +1042,7 @@
                                                       "nop instruction");
   }
 
-  if (MCID.hasDelaySlot() && Options.isReorder()) {
+  if (MCID.hasDelaySlot() && AssemblerOptions.top()->isReorder()) {
     // If this instruction has a delay slot and .set reorder is active,
     // emit a NOP after it.
     Instructions.push_back(Inst);
@@ -1468,7 +1505,8 @@
 }
 
 void MipsAsmParser::WarnIfAssemblerTemporary(int RegIndex, SMLoc Loc) {
-  if ((RegIndex != 0) && ((int)Options.getATRegNum() == RegIndex)) {
+  if ((RegIndex != 0) && 
+      ((int)AssemblerOptions.top()->getATRegNum() == RegIndex)) {
     if (RegIndex == 1)
       Warning(Loc, "Used $at without \".set noat\"");
     else
@@ -1617,7 +1655,7 @@
 }
 
 int MipsAsmParser::getATReg(SMLoc Loc) {
-  int AT = Options.getATRegNum();
+  int AT = AssemblerOptions.top()->getATRegNum();
   if (AT == 0)
     reportParseError(Loc,
                      "Pseudo instruction requires $at, which is not available");
@@ -2372,7 +2410,7 @@
 bool MipsAsmParser::parseSetNoAtDirective() {
   // Line should look like: ".set noat".
   // set at reg to 0.
-  Options.setATReg(0);
+  AssemblerOptions.top()->setATReg(0);
   // eat noat
   Parser.Lex();
   // If this is not the end of the statement, report an error.
@@ -2390,7 +2428,7 @@
   int AtRegNo;
   getParser().Lex();
   if (getLexer().is(AsmToken::EndOfStatement)) {
-    Options.setATReg(1);
+    AssemblerOptions.top()->setATReg(1);
     Parser.Lex(); // Consume the EndOfStatement.
     return false;
   } else if (getLexer().is(AsmToken::Equal)) {
@@ -2415,7 +2453,7 @@
       return false;
     }
 
-    if (!Options.setATReg(AtRegNo)) {
+    if (!AssemblerOptions.top()->setATReg(AtRegNo)) {
       reportParseError("unexpected token in statement");
       return false;
     }
@@ -2440,7 +2478,7 @@
     reportParseError("unexpected token in statement");
     return false;
   }
-  Options.setReorder();
+  AssemblerOptions.top()->setReorder();
   getTargetStreamer().emitDirectiveSetReorder();
   Parser.Lex(); // Consume the EndOfStatement.
   return false;
@@ -2453,7 +2491,7 @@
     reportParseError("unexpected token in statement");
     return false;
   }
-  Options.setNoreorder();
+  AssemblerOptions.top()->setNoreorder();
   getTargetStreamer().emitDirectiveSetNoReorder();
   Parser.Lex(); // Consume the EndOfStatement.
   return false;
@@ -2466,7 +2504,7 @@
     reportParseError("unexpected token in statement");
     return false;
   }
-  Options.setMacro();
+  AssemblerOptions.top()->setMacro();
   Parser.Lex(); // Consume the EndOfStatement.
   return false;
 }
@@ -2478,11 +2516,11 @@
     reportParseError("`noreorder' must be set before `nomacro'");
     return false;
   }
-  if (Options.isReorder()) {
+  if (AssemblerOptions.top()->isReorder()) {
     reportParseError("`noreorder' must be set before `nomacro'");
     return false;
   }
-  Options.setNomacro();
+  AssemblerOptions.top()->setNomacro();
   Parser.Lex(); // Consume the EndOfStatement.
   return false;
 }
@@ -2525,6 +2563,34 @@
   return false;
 }
 
+bool MipsAsmParser::parseSetPopDirective() {
+  SMLoc Loc = getLexer().getLoc();
+
+  Parser.Lex();
+  if (getLexer().isNot(AsmToken::EndOfStatement))
+    return reportParseError("unexpected token in .set pop directive");
+
+  if (AssemblerOptions.size() == 1)
+    return reportParseError(Loc, ".set pop with no .set push");
+
+  AssemblerOptions.pop();  
+  setAvailableFeatures(AssemblerOptions.top()->getCurrentFeatures());
+  
+  getTargetStreamer().emitDirectiveSetPop();
+  return false;
+}
+
+bool MipsAsmParser::parseSetPushDirective() {
+  Parser.Lex();
+  if (getLexer().isNot(AsmToken::EndOfStatement))
+    return reportParseError("unexpected token in .set push directive");
+
+  AssemblerOptions.push(new MipsAssemblerOptions(AssemblerOptions.top()));
+
+  getTargetStreamer().emitDirectiveSetPush();
+  return false;
+}
+
 bool MipsAsmParser::parseSetAssignment() {
   StringRef Name;
   const MCExpr *Value;
@@ -2627,7 +2693,7 @@
 }
 
 bool MipsAsmParser::parseDirectiveCPLoad(SMLoc Loc) {
-  if (Options.isReorder())
+  if (AssemblerOptions.top()->isReorder())
     Warning(Loc, ".cpload in reorder section");
 
   // FIXME: Warn if cpload is used in Mips16 mode.
@@ -2740,6 +2806,10 @@
     return parseSetAtDirective();
   } else if (Tok.getString() == "fp") {
     return parseSetFpDirective();
+  } else if (Tok.getString() == "pop") {
+    return parseSetPopDirective();
+  } else if (Tok.getString() == "push") {
+    return parseSetPushDirective();
   } else if (Tok.getString() == "reorder") {
     return parseSetReorderDirective();
   } else if (Tok.getString() == "noreorder") {
Index: lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
===================================================================
--- lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
+++ lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
@@ -64,6 +64,8 @@
 void MipsTargetStreamer::emitDirectiveSetMips64R2() {}
 void MipsTargetStreamer::emitDirectiveSetMips64R6() {}
 void MipsTargetStreamer::emitDirectiveSetDsp() {}
+void MipsTargetStreamer::emitDirectiveSetPop() {}
+void MipsTargetStreamer::emitDirectiveSetPush() {}
 void MipsTargetStreamer::emitDirectiveCpload(unsigned RegNo) {}
 void MipsTargetStreamer::emitDirectiveCpsetup(unsigned RegNo, int RegOrOffset,
                                               const MCSymbol &Sym, bool IsReg) {
@@ -219,6 +221,11 @@
   OS << "\t.set\tdsp\n";
   setCanHaveModuleDir(false);
 }
+
+void MipsTargetAsmStreamer::emitDirectiveSetPop() { OS << "\t.set\tpop\n"; }
+
+void MipsTargetAsmStreamer::emitDirectiveSetPush() { OS << "\t.set\tpush\n"; }
+
 // Print a 32 bit hex number with all numbers.
 static void printHex32(unsigned Value, raw_ostream &OS) {
   OS << "0x";
Index: lib/Target/Mips/MipsTargetStreamer.h
===================================================================
--- lib/Target/Mips/MipsTargetStreamer.h
+++ lib/Target/Mips/MipsTargetStreamer.h
@@ -57,6 +57,8 @@
   virtual void emitDirectiveSetMips64R2();
   virtual void emitDirectiveSetMips64R6();
   virtual void emitDirectiveSetDsp();
+  virtual void emitDirectiveSetPop();
+  virtual void emitDirectiveSetPush();
 
   // PIC support
   virtual void emitDirectiveCpload(unsigned RegNo);
@@ -141,6 +143,8 @@
   void emitDirectiveSetMips64R2() override;
   void emitDirectiveSetMips64R6() override;
   void emitDirectiveSetDsp() override;
+  void emitDirectiveSetPop() override;
+  void emitDirectiveSetPush() override;
 
   // PIC support
   virtual void emitDirectiveCpload(unsigned RegNo);
Index: test/MC/Mips/set-push-pop-directives-bad.s
===================================================================
--- /dev/null
+++ test/MC/Mips/set-push-pop-directives-bad.s
@@ -0,0 +1,14 @@
+# RUN: not llvm-mc %s -triple=mipsel-unknown-linux -mcpu=mips32r2 2>%t1
+# RUN: FileCheck %s < %t1
+
+        .text
+        .set pop
+# CHECK: :[[@LINE-1]]:14: error: .set pop with no .set push
+        .set push
+        .set pop
+        .set pop
+# CHECK: :[[@LINE-1]]:14: error: .set pop with no .set push
+        .set push foo
+# CHECK: :[[@LINE-1]]:19: error: unexpected token in .set push directive
+        .set pop bar
+# CHECK: :[[@LINE-1]]:18: error: unexpected token in .set pop directive
Index: test/MC/Mips/set-push-pop-directives.s
===================================================================
--- /dev/null
+++ test/MC/Mips/set-push-pop-directives.s
@@ -0,0 +1,50 @@
+## This test checks that .set push and .set pop work as they should i.e.,
+## '.set push' creates a new environment with the same properties of the
+## old one and '.set pop' restores the old environment.
+# RUN: llvm-mc %s -triple=mipsel-unknown-linux -show-encoding -mcpu=mips32 | \
+# RUN: FileCheck %s
+
+    .text
+    .set noreorder
+    .set at=$ra
+    .set push
+    lw $1, 65536($1)
+    b  1336
+    .set reorder
+    b  1336
+    .set pop
+    b  1332
+
+# Now let's check the .set mipsx directives...
+# The -mcpu=mips32 option was specified on the command-line which means the current
+# arch is mips32.
+    .set push
+    .set mips32r2
+    .set push
+    .set mips32
+    .set pop
+# ARCH should be mips32r2 at this point. We must be able to assemble a mips32r2 instruction
+    ldxc1 $f0, $zero($5)
+    .set pop
+
+# CHECK: .text
+# CHECK: .set noreorder
+# CHECK: .set push
+# CHECK: lui $ra, 1
+# CHECK: addu $ra, $ra, $1
+# CHECK: lw $1, 0($ra)
+# CHECK: b 1336
+# CHECK-NOT: nop
+# CHECK: .set reorder
+# CHECK: b 1336
+# CHECK-NEXT: nop
+# CHECK: .set pop
+# CHECK: b 1332
+# CHECK-NOT: nop
+
+# CHECK: .set push
+# CHECK: .set mips32r2
+# CHECK: .set push
+# CHECK: .set mips32
+# CHECK: ldxc1 $f0, $zero($5)
+# CHECK: .set pop