diff --git a/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp b/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
--- a/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
+++ b/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
@@ -182,6 +182,11 @@
   bool parseDirectiveInsn(SMLoc L);
   bool parseDirectiveVariantCC();
 
+  /// Helper to reset target features for a new arch string. It
+  /// also records the new arch string that expanded by RISCVISAInfo
+  /// and reports error for invalid arch string
+  bool resetToArch(StringRef Arch, SMLoc Loc, std::string &Result);
+
   void setFeatureBits(uint64_t Feature, StringRef FeatureString) {
     if (!(getSTI().hasFeature(Feature))) {
       MCSubtargetInfo &STI = copySTI();
@@ -2117,6 +2122,42 @@
   return true;
 }
 
+bool RISCVAsmParser::resetToArch(StringRef Arch, SMLoc Loc,
+                                 std::string &Result) {
+  for (auto Feature : RISCVFeatureKV)
+    if (llvm::RISCVISAInfo::isSupportedExtensionFeature(Feature.Key))
+      clearFeatureBits(Feature.Value, Feature.Key);
+
+  auto ParseResult = llvm::RISCVISAInfo::parseArchString(
+      Arch, /*EnableExperimentalExtension=*/true,
+      /*ExperimentalExtensionVersionCheck=*/true);
+  if (!ParseResult) {
+    std::string Buffer;
+    raw_string_ostream OutputErrMsg(Buffer);
+    handleAllErrors(ParseResult.takeError(), [&](llvm::StringError &ErrMsg) {
+      OutputErrMsg << "invalid arch name '" << Arch << "', "
+                   << ErrMsg.getMessage();
+    });
+
+    return Error(Loc, OutputErrMsg.str());
+  }
+  auto &ISAInfo = *ParseResult;
+
+  for (auto Feature : RISCVFeatureKV)
+    if (ISAInfo->hasExtension(Feature.Key))
+      setFeatureBits(Feature.Value, Feature.Key);
+
+  if (ISAInfo->getXLen() == 32)
+    clearFeatureBits(RISCV::Feature64Bit, "64bit");
+  else if (ISAInfo->getXLen() == 64)
+    setFeatureBits(RISCV::Feature64Bit, "64bit");
+  else
+    return Error(Loc, "bad arch string " + Arch);
+
+  Result = ISAInfo->toString();
+  return false;
+}
+
 bool RISCVAsmParser::parseDirectiveOption() {
   MCAsmParser &Parser = getParser();
   // Get the option token.
@@ -2149,6 +2190,105 @@
     return false;
   }
 
+  if (Option == "arch") {
+
+    Parser.parseComma();
+
+    bool PrefixEmitted = false;
+    bool IsExtensionList = false;
+    bool IsFullArchString = false;
+    while (true) {
+      bool IsAdd;
+      if (Parser.getTok().is(AsmToken::Plus)) {
+        IsAdd = true;
+        IsExtensionList = true;
+      } else if (Parser.getTok().is(AsmToken::Minus)) {
+        IsAdd = false;
+        IsExtensionList = true;
+      } else {
+        IsFullArchString = true;
+        SMLoc ArchLoc = Parser.getTok().getLoc();
+
+        if (IsExtensionList)
+          return Error(
+              ArchLoc,
+              "mix extension list with full arch string is not allowed!");
+
+        if (Parser.getTok().isNot(AsmToken::String))
+          return Error(ArchLoc, "unexpected token, expected string");
+
+        StringRef Arch = Parser.getTok().getStringContents();
+        std::string Result;
+        if (resetToArch(Arch, ArchLoc, Result))
+          return true;
+
+        Parser.Lex();
+        bool HasComma = getTok().is(AsmToken::Comma);
+        getTargetStreamer().emitDirectiveOptionArchEqual(Result, PrefixEmitted,
+                                                         HasComma);
+
+        if (HasComma) {
+          Parser.Lex();
+          continue;
+        }
+        return Parser.parseToken(AsmToken::EndOfStatement,
+                                 "unexpected token, expected end of statement");
+      }
+
+      if (IsFullArchString)
+        return Error(
+            Parser.getTok().getLoc(),
+            "mix extension list with full arch string is not allowed!");
+
+      Parser.Lex();
+
+      if (Parser.getTok().isNot(AsmToken::Identifier))
+        return Error(Parser.getTok().getLoc(),
+                     "unexpected token, expected identifier");
+
+      StringRef ExtStr = Parser.getTok().getString();
+
+      if (ExtStr.find_if(isDigit) != StringRef::npos)
+        return Error(Parser.getTok().getLoc(),
+                     "Don't specify version number, extensions don't rely on "
+                     "version numbers");
+
+      ArrayRef<SubtargetFeatureKV> KVArray(RISCVFeatureKV);
+      auto Ext = llvm::lower_bound(KVArray, ExtStr);
+      if (Ext == KVArray.end() || StringRef(Ext->Key) != ExtStr)
+        return Error(Parser.getTok().getLoc(), "unknown extension");
+
+      Parser.Lex(); // Eat arch string
+      bool HasComma = getTok().is(AsmToken::Comma);
+      if (IsAdd) {
+        setFeatureBits(Ext->Value, Ext->Key);
+        getTargetStreamer().emitDirectiveOptionArchPlus(Ext->Key, PrefixEmitted,
+                                                        HasComma);
+      } else {
+        // Check dependency. It is invalid to disable an extension that
+        // there are other enabled extensions depend on it.
+        for (auto Feature : KVArray) {
+          if (getSTI().hasFeature(Feature.Value) &&
+              Feature.Implies.test(Ext->Value))
+            return Error(Parser.getTok().getLoc(),
+                         Twine("Can't disable ") + Ext->Key + " extension, " +
+                             Feature.Key + " extension requires " + Ext->Key +
+                             " extension be enabled");
+        }
+
+        clearFeatureBits(Ext->Value, Ext->Key);
+        getTargetStreamer().emitDirectiveOptionArchMinus(
+            Ext->Key, PrefixEmitted, HasComma);
+      }
+
+      if (!HasComma)
+        return Parser.parseToken(AsmToken::EndOfStatement,
+                                 "unexpected token, expected end of statement");
+      // Eat comma
+      Parser.Lex();
+    }
+  }
+
   if (Option == "rvc") {
     if (Parser.parseEOL())
       return true;
@@ -2205,9 +2345,9 @@
   }
 
   // Unknown option.
-  Warning(Parser.getTok().getLoc(),
-          "unknown option, expected 'push', 'pop', 'rvc', 'norvc', 'relax' or "
-          "'norelax'");
+  Warning(Parser.getTok().getLoc(), "unknown option, expected 'push', 'pop', "
+                                    "'rvc', 'norvc', 'arch', 'relax' or "
+                                    "'norelax'");
   Parser.eatToEndOfStatement();
   return false;
 }
@@ -2282,39 +2422,12 @@
   else if (Tag != RISCVAttrs::ARCH)
     getTargetStreamer().emitTextAttribute(Tag, StringValue);
   else {
-    StringRef Arch = StringValue;
-    for (auto Feature : RISCVFeatureKV)
-      if (llvm::RISCVISAInfo::isSupportedExtensionFeature(Feature.Key))
-        clearFeatureBits(Feature.Value, Feature.Key);
-
-    auto ParseResult = llvm::RISCVISAInfo::parseArchString(
-        StringValue, /*EnableExperimentalExtension=*/true,
-        /*ExperimentalExtensionVersionCheck=*/true);
-    if (!ParseResult) {
-      std::string Buffer;
-      raw_string_ostream OutputErrMsg(Buffer);
-      handleAllErrors(ParseResult.takeError(), [&](llvm::StringError &ErrMsg) {
-        OutputErrMsg << "invalid arch name '" << Arch << "', "
-                     << ErrMsg.getMessage();
-      });
-
-      return Error(ValueExprLoc, OutputErrMsg.str());
-    }
-    auto &ISAInfo = *ParseResult;
-
-    for (auto Feature : RISCVFeatureKV)
-      if (ISAInfo->hasExtension(Feature.Key))
-        setFeatureBits(Feature.Value, Feature.Key);
-
-    if (ISAInfo->getXLen() == 32)
-      clearFeatureBits(RISCV::Feature64Bit, "64bit");
-    else if (ISAInfo->getXLen() == 64)
-      setFeatureBits(RISCV::Feature64Bit, "64bit");
-    else
-      return Error(ValueExprLoc, "bad arch string " + Arch);
+    std::string Result;
+    if (resetToArch(StringValue, ValueExprLoc, Result))
+      return true;
 
     // Then emit the arch string.
-    getTargetStreamer().emitTextAttribute(Tag, ISAInfo->toString());
+    getTargetStreamer().emitTextAttribute(Tag, Result);
   }
 
   return false;
diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVTargetStreamer.h b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVTargetStreamer.h
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVTargetStreamer.h
+++ b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVTargetStreamer.h
@@ -34,6 +34,14 @@
   virtual void emitDirectiveOptionRelax();
   virtual void emitDirectiveOptionNoRelax();
   virtual void emitDirectiveVariantCC(MCSymbol &Symbol);
+  virtual void emitDirectiveOptionArchEqual(StringRef Value,
+                                            bool &PrefixEmitted,
+                                            bool EmitComma);
+  virtual void emitDirectiveOptionArchPlus(StringRef Value, bool &PrefixEmitted,
+                                           bool EmitComma);
+  virtual void emitDirectiveOptionArchMinus(StringRef Value,
+                                            bool &PrefixEmitted,
+                                            bool EmitComma);
   virtual void emitAttribute(unsigned Attribute, unsigned Value);
   virtual void finishAttributeSection();
   virtual void emitTextAttribute(unsigned Attribute, StringRef String);
@@ -67,6 +75,12 @@
   void emitDirectiveOptionRelax() override;
   void emitDirectiveOptionNoRelax() override;
   void emitDirectiveVariantCC(MCSymbol &Symbol) override;
+  void emitDirectiveOptionArchEqual(StringRef Value, bool &PrefixEmitted,
+                                    bool EmitComma) override;
+  void emitDirectiveOptionArchPlus(StringRef Value, bool &PrefixEmitted,
+                                   bool EmitComma) override;
+  void emitDirectiveOptionArchMinus(StringRef Value, bool &PrefixEmitted,
+                                    bool EmitComma) override;
 };
 
 }
diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVTargetStreamer.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVTargetStreamer.cpp
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVTargetStreamer.cpp
+++ b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVTargetStreamer.cpp
@@ -34,6 +34,15 @@
 void RISCVTargetStreamer::emitDirectiveOptionRelax() {}
 void RISCVTargetStreamer::emitDirectiveOptionNoRelax() {}
 void RISCVTargetStreamer::emitDirectiveVariantCC(MCSymbol &Symbol) {}
+void RISCVTargetStreamer::emitDirectiveOptionArchEqual(StringRef Value,
+                                                       bool &hasDotOption,
+                                                       bool EmitComma) {}
+void RISCVTargetStreamer::emitDirectiveOptionArchPlus(StringRef Value,
+                                                      bool &hasDotOption,
+                                                      bool EmitComma) {}
+void RISCVTargetStreamer::emitDirectiveOptionArchMinus(StringRef Value,
+                                                       bool &hasDotOption,
+                                                       bool EmitComma) {}
 void RISCVTargetStreamer::emitAttribute(unsigned Attribute, unsigned Value) {}
 void RISCVTargetStreamer::finishAttributeSection() {}
 void RISCVTargetStreamer::emitTextAttribute(unsigned Attribute,
@@ -116,4 +125,41 @@
                                                   unsigned IntValue,
                                                   StringRef StringValue) {}
 
+static void emitDirectiveOptionArchPrefix(formatted_raw_ostream &OS,
+                                          bool &PrefixEmitted) {
+  if (!PrefixEmitted) {
+    OS << "\t .option\tarch,\t";
+    PrefixEmitted = true;
+  }
+}
+
+static void emitCommaOrNextLine(formatted_raw_ostream &OS, bool EmitComma) {
+  if (EmitComma)
+    OS << ", ";
+  else
+    OS << "\n";
+}
+
+void RISCVTargetAsmStreamer::emitDirectiveOptionArchEqual(StringRef Value,
+                                                          bool &PrefixEmitted,
+                                                          bool EmitComma) {
+  emitDirectiveOptionArchPrefix(OS, PrefixEmitted);
+  OS << "\"" << Value << "\"";
+  emitCommaOrNextLine(OS, EmitComma);
+}
+void RISCVTargetAsmStreamer::emitDirectiveOptionArchPlus(StringRef Value,
+                                                         bool &PrefixEmitted,
+                                                         bool EmitComma) {
+  emitDirectiveOptionArchPrefix(OS, PrefixEmitted);
+  OS << "+" << Value;
+  emitCommaOrNextLine(OS, EmitComma);
+}
+void RISCVTargetAsmStreamer::emitDirectiveOptionArchMinus(StringRef Value,
+                                                          bool &PrefixEmitted,
+                                                          bool EmitComma) {
+  emitDirectiveOptionArchPrefix(OS, PrefixEmitted);
+  OS << "-" << Value;
+  emitCommaOrNextLine(OS, EmitComma);
+}
+
 void RISCVTargetAsmStreamer::finishAttributeSection() {}
diff --git a/llvm/test/MC/RISCV/option-arch.s b/llvm/test/MC/RISCV/option-arch.s
new file mode 100644
--- /dev/null
+++ b/llvm/test/MC/RISCV/option-arch.s
@@ -0,0 +1,96 @@
+# RUN: llvm-mc -triple riscv32 -show-encoding < %s \
+# RUN:   | FileCheck -check-prefixes=CHECK,CHECK-ALIAS %s
+# RUN: llvm-mc -triple riscv32 -show-encoding \
+# RUN:   -riscv-no-aliases < %s | FileCheck -check-prefixes=CHECK,CHECK-INST %s
+# RUN: llvm-mc -triple riscv32 -filetype=obj < %s \
+# RUN:   | llvm-objdump  --triple=riscv32 --mattr=+c -d - \
+# RUN:   | FileCheck -check-prefixes=CHECK-BYTES,CHECK-ALIAS %s
+# RUN: llvm-mc -triple riscv32 -filetype=obj < %s \
+# RUN:   | llvm-objdump  --triple=riscv32 --mattr=+c -d -M no-aliases - \
+# RUN:   | FileCheck -check-prefixes=CHECK-BYTES,CHECK-INST %s
+
+# RUN: llvm-mc -triple riscv64 -show-encoding < %s \
+# RUN:   | FileCheck -check-prefixes=CHECK-ALIAS %s
+# RUN: llvm-mc -triple riscv64 -show-encoding \
+# RUN:   -riscv-no-aliases < %s | FileCheck -check-prefixes=CHECK-INST %s
+# RUN: llvm-mc -triple riscv64 -filetype=obj < %s \
+# RUN:   | llvm-objdump  --triple=riscv64 --mattr=+c -d - \
+# RUN:   | FileCheck -check-prefixes=CHECK-BYTES,CHECK-ALIAS %s
+# RUN: llvm-mc -triple riscv64 -filetype=obj < %s \
+# RUN:   | llvm-objdump  --triple=riscv64 --mattr=+c -d -M no-aliases - \
+# RUN:   | FileCheck -check-prefixes=CHECK-BYTES,CHECK-INST %s
+
+# Test '.option arch, +' and '.option arch, -' directive
+# The following test cases were copied from MC/RISCV/option-rvc.s
+
+# CHECK-BYTES: 13 85 05 00
+# CHECK-ALIAS: mv a0, a1
+# CHECK-INST: addi a0, a1, 0
+# CHECK: # encoding:  [0x13,0x85,0x05,0x00]
+addi a0, a1, 0
+
+# CHECK-BYTES: 13 04 c1 3f
+# CHECK-ALIAS: addi s0, sp, 1020
+# CHECK-INST: addi s0, sp, 1020
+# CHECK: # encoding:  [0x13,0x04,0xc1,0x3f]
+addi s0, sp, 1020
+
+# CHECK: .option arch, +c
+.option arch, +c
+# CHECK-BYTES: 2e 85
+# CHECK-ALIAS: mv a0, a1
+# CHECK-INST: c.mv a0, a1
+# CHECK: # encoding:  [0x2e,0x85]
+addi a0, a1, 0
+
+# CHECK-BYTES: e0 1f
+# CHECK-ALIAS: addi s0, sp, 1020
+# CHECK-INST: c.addi4spn s0, sp, 1020
+# CHECK: # encoding:  [0xe0,0x1f]
+addi s0, sp, 1020
+
+# CHECK: .option arch, -c
+.option arch, -c
+# CHECK-BYTES: 13 85 05 00
+# CHECK-ALIAS: mv a0, a1
+# CHECK-INST: addi a0, a1, 0
+# CHECK: # encoding:  [0x13,0x85,0x05,0x00]
+addi a0, a1, 0
+
+# CHECK-BYTES: 13 04 c1 3f
+# CHECK-ALIAS: addi s0, sp, 1020
+# CHECK-INST: addi s0, sp, 1020
+# CHECK: # encoding:  [0x13,0x04,0xc1,0x3f]
+addi s0, sp, 1020
+
+# CHECK: .option arch, +c
+.option arch, +c
+# CHECK-BYTES: 2e 85
+# CHECK-ALIAS: mv a0, a1
+# CHECK-INST: c.mv a0, a1
+# CHECK: # encoding:  [0x2e,0x85]
+addi a0, a1, 0
+
+# CHECK-BYTES: e0 1f
+# CHECK-ALIAS: addi s0, sp, 1020
+# CHECK-INST: c.addi4spn s0, sp, 1020
+# CHECK: # encoding:  [0xe0,0x1f]
+addi s0, sp, 1020
+
+# CHECK: .option arch, -c
+.option arch, -c
+# CHECK-BYTES: 13 85 05 00
+# CHECK-ALIAS: mv a0, a1
+# CHECK-INST: addi a0, a1, 0
+# CHECK: # encoding:  [0x13,0x85,0x05,0x00]
+addi a0, a1, 0
+
+# CHECK-BYTES: 13 04 c1 3f
+# CHECK-ALIAS: addi s0, sp, 1020
+# CHECK-INST: addi s0, sp, 1020
+# CHECK: # encoding:  [0x13,0x04,0xc1,0x3f]
+addi s0, sp, 1020
+
+# Test '.option arch, <arch-stringg>' directive
+#CHECK: .option arch, "rv32i2p0_m2p0_a2p0_c2p0"
+.option arch, "rv32i2p0_m2p0_a2p0_c2p0"
diff --git a/llvm/test/MC/RISCV/option-invalid.s b/llvm/test/MC/RISCV/option-invalid.s
--- a/llvm/test/MC/RISCV/option-invalid.s
+++ b/llvm/test/MC/RISCV/option-invalid.s
@@ -13,7 +13,35 @@
 # CHECK: :[[#@LINE+1]]:13: error: expected newline
 .option rvc foo
 
-# CHECK: :[[#@LINE+1]]:12: warning: unknown option, expected 'push', 'pop', 'rvc', 'norvc', 'relax' or 'norelax'
+# CHECK: :[[#@LINE+1]]:15: error: unexpected token, expected string
+.option arch, rv32i
+
+# CHECK: :[[#@LINE+1]]:23: error: mix extension list with full arch string is not allowed!
+.option arch, +f, +d, "rv32ifd", -d
+
+# CHECK: :[[#@LINE+1]]:16: error: unexpected token, expected identifier
+.option arch, +"c"
+
+# CHECK: :[[#@LINE+1]]:16: error: unknown extension
+.option arch, +x
+
+# CHECK: :[[#@LINE+1]]:23: error: unexpected token, expected end of statement
+.option arch, "rv32i" foo
+
+# CHECK: :[[#@LINE+1]]:18: error: unexpected token, expected end of statement
+.option arch, +c foo
+
+# CHECK: :[[#@LINE+1]]:16: error: Don't specify version number, extensions don't rely on version numbers
+.option arch, +c2p0
+
+.option arch, +d
+# CHECK: :[[#@LINE+1]]:17: error: Can't disable f extension, d extension requires f extension be enabled
+.option arch, -f
+
+# CHECK: :[[#@LINE+1]]:13: error: expected newline
+.option rvc foo
+
+# CHECK: :[[#@LINE+1]]:12: warning: unknown option, expected 'push', 'pop', 'rvc', 'norvc', 'arch', 'relax' or 'norelax'
 .option bar
 
 # CHECK: :[[#@LINE+1]]:12: error: .option pop with no .option push