diff --git a/clang/test/Driver/riscv-arch.c b/clang/test/Driver/riscv-arch.c
index ffd92e1f398c45..0f285f7c0033cf 100644
--- a/clang/test/Driver/riscv-arch.c
+++ b/clang/test/Driver/riscv-arch.c
@@ -306,7 +306,7 @@
 // RUN: not %clang --target=riscv32-unknown-elf -march=rv32ixabc_ -### %s \
 // RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=RV32-XSEP %s
 // RV32-XSEP: error: invalid arch name 'rv32ixabc_',
-// RV32-XSEP: extension name missing after separator '_'
+// RV32-XSEP: unsupported non-standard user-level extension 'xabc'
 
 // RUN: not %clang --target=riscv32-unknown-elf -march=rv32ixabc_a -### %s \
 // RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=RV32-PREFIX %s
@@ -318,10 +318,10 @@
 // RV32-X-ORDER: error: invalid arch name 'rv32ixdef_sabc',
 // RV32-X-ORDER  unsupported non-standard user-level extension 'xdef'
 
-// RUN: not %clang --target=riscv32-unknown-elf -march=rv32ixabc_xabc -### %s \
+// RUN: not %clang --target=riscv32-unknown-elf -march=rv32im_m -### %s \
 // RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=RV32-XDUP %s
-// RV32-XDUP: error: invalid arch name 'rv32ixabc_xabc',
-// RV32-XDUP: duplicated non-standard user-level extension 'xabc'
+// RV32-XDUP: error: invalid arch name 'rv32im_m',
+// RV32-XDUP: duplicated standard user-level extension 'm'
 
 // RUN: not %clang --target=riscv32-unknown-elf -march=rv32ixabc_xdef -### %s \
 // RUN: -fsyntax-only 2>&1 | FileCheck -check-prefix=RV32-X-X-INVAL %s
diff --git a/llvm/lib/TargetParser/RISCVISAInfo.cpp b/llvm/lib/TargetParser/RISCVISAInfo.cpp
index 133c6852bc85e8..ee8024b3bea36c 100644
--- a/llvm/lib/TargetParser/RISCVISAInfo.cpp
+++ b/llvm/lib/TargetParser/RISCVISAInfo.cpp
@@ -7,9 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/TargetParser/RISCVISAInfo.h"
-#include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/STLExtras.h"
-#include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Errc.h"
@@ -558,9 +556,6 @@ RISCVISAInfo::parseArchString(StringRef Arch, bool EnableExperimentalExtension,
         "profile name");
 
   std::unique_ptr<RISCVISAInfo> ISAInfo(new RISCVISAInfo(XLen));
-  MapVector<std::string, RISCVISAUtils::ExtensionVersion,
-            std::map<std::string, unsigned>>
-      SeenExtMap;
 
   // The canonical order specified in ISA manual.
   // Ref: Table 22.1 in RISC-V User-Level ISA V2.2
@@ -583,8 +578,7 @@ RISCVISAInfo::parseArchString(StringRef Arch, bool EnableExperimentalExtension,
             EnableExperimentalExtension, ExperimentalExtensionVersionCheck))
       return std::move(E);
 
-    // Postpone AddExtension until end of this function
-    SeenExtMap[StringRef(&Baseline, 1).str()] = {Major, Minor};
+    ISAInfo->Exts[std::string(1, Baseline)] = {Major, Minor};
     break;
   case 'g':
     // g expands to extensions in RISCVGImplications.
@@ -597,11 +591,11 @@ RISCVISAInfo::parseArchString(StringRef Arch, bool EnableExperimentalExtension,
     // No matter which version is given to `g`, we always set imafd to default
     // version since the we don't have clear version scheme for that on
     // ISA spec.
-    for (const auto *Ext : RISCVGImplications) {
+    for (const char *Ext : RISCVGImplications) {
       auto Version = findDefaultVersion(Ext);
       assert(Version && "Default extension version not found?");
       // Postpone AddExtension until end of this function
-      SeenExtMap[Ext] = {Version->Major, Version->Minor};
+      ISAInfo->Exts[std::string(Ext)] = {Version->Major, Version->Minor};
     }
     break;
   }
@@ -662,23 +656,19 @@ RISCVISAInfo::parseArchString(StringRef Arch, bool EnableExperimentalExtension,
       if (Name.size() == 1)
         Ext = Ext.substr(ConsumeLength);
 
-      // Check if duplicated extension.
-      if (SeenExtMap.contains(Name.str()))
+      if (!RISCVISAInfo::isSupportedExtension(Name))
+        return getErrorForInvalidExt(Name);
+
+      // Insert and error for duplicates.
+      if (!ISAInfo->Exts
+               .emplace(Name.str(),
+                        RISCVISAUtils::ExtensionVersion{Major, Minor})
+               .second)
         return getError("duplicated " + Desc + " '" + Name + "'");
 
-      SeenExtMap[Name.str()] = {Major, Minor};
     } while (!Ext.empty());
   }
 
-  // Check all Extensions are supported.
-  for (auto &SeenExtAndVers : SeenExtMap) {
-    const std::string &ExtName = SeenExtAndVers.first;
-
-    if (!RISCVISAInfo::isSupportedExtension(ExtName))
-      return getErrorForInvalidExt(ExtName);
-    ISAInfo->Exts[ExtName] = SeenExtAndVers.second;
-  }
-
   return RISCVISAInfo::postProcessAndChecking(std::move(ISAInfo));
 }