[RISCV] Detect duplicate extensions in parseNormalizedArchString. (#91416)

This detects the same extension name being added twice. Mostly I'm
worried about the case that the same string appears with two different
versions. We will only preserve one of the versions.

We could allow the same version to be repeated, but that doesn't seem
useful at the moment.

I've updated addExtension to use map::emplace instead of
map::operator[]. This means we only keep the first version if there are
duplicates. Previously we kept the last version, but that shouldn't matter
now that we don't allow duplicates. parseArchString already doesn't allow
duplicates.

Author: topperc

llvm/include/llvm/TargetParser/RISCVISAInfo.h

@@ -87,7 +87,7 @@ class RISCVISAInfo {
 
   RISCVISAUtils::OrderedExtensionMap Exts;
 
-  void addExtension(StringRef ExtName, RISCVISAUtils::ExtensionVersion Version);
+  bool addExtension(StringRef ExtName, RISCVISAUtils::ExtensionVersion Version);
 
   Error checkDependency();
 

llvm/lib/TargetParser/RISCVISAInfo.cpp

@@ -159,9 +159,9 @@ findDefaultVersion(StringRef ExtName) {
   return std::nullopt;
 }
 
-void RISCVISAInfo::addExtension(StringRef ExtName,
+bool RISCVISAInfo::addExtension(StringRef ExtName,
                                 RISCVISAUtils::ExtensionVersion Version) {
-  Exts[ExtName.str()] = Version;
+  return Exts.emplace(ExtName, Version).second;
 }
 
 static StringRef getExtensionTypeDesc(StringRef Ext) {
@@ -492,7 +492,9 @@ RISCVISAInfo::parseNormalizedArchString(StringRef Arch) {
                                "'" + Twine(ExtName[0]) +
                                    "' must be followed by a letter");
 
-    ISAInfo->addExtension(ExtName, {MajorVersion, MinorVersion});
+    if (!ISAInfo->addExtension(ExtName, {MajorVersion, MinorVersion}))
+      return createStringError(errc::invalid_argument,
+                               "duplicate extension '" + ExtName + "'");
   }
   ISAInfo->updateImpliedLengths();
   return std::move(ISAInfo);

llvm/unittests/TargetParser/RISCVISAInfoTest.cpp

@@ -78,6 +78,14 @@ TEST(ParseNormalizedArchString, RejectsBadX) {
   }
 }
 
+TEST(ParseNormalizedArchString, DuplicateExtension) {
+  for (StringRef Input : {"rv64i2p0_a2p0_a1p0"}) {
+    EXPECT_EQ(
+        toString(RISCVISAInfo::parseNormalizedArchString(Input).takeError()),
+        "duplicate extension 'a'");
+  }
+}
+
 TEST(ParseNormalizedArchString, AcceptsValidBaseISAsAndSetsXLen) {
   auto MaybeRV32I = RISCVISAInfo::parseNormalizedArchString("rv32i2p0");
   ASSERT_THAT_EXPECTED(MaybeRV32I, Succeeded());