[RISCV] Fix gaps in IgnoreUnknown=true for RISCVISAInfo::parseArchString

[asb]

Summary

Prior to this patch, unrecognised z/s/sx/x prefixed extensions were not ignored when IgnoreUnknown=true.

[kito-cheng]

LGTM :)

llvm/lib/Support/RISCVISAInfo.cpp

for (StringRef Ext : Split) {
       }
 
       // Check if duplicated extension.
       if (!IgnoreUnknown && llvm::is_contained(AllExts, Name)) {
         return createStringError(errc::invalid_argument, "duplicated %s '%s'",
                                  Desc.str().c_str(), Name.str().c_str());
       }
 
+      if (IgnoreUnknown && !isSupportedExtension(Ext))
+        continue;
+
       ISAInfo->addExtension(Name, Major, Minor);
       // Extension format is correct, keep parsing the extensions.
       // TODO: Save Type, Name, Major, Minor to avoid parsing them later.
       AllExts.push_back(Name);
     }
   }
 
   for (auto Ext : AllExts) {

llvm/unittests/Support/RISCVISAInfoTest.cpp

EXPECT_EQ(
       "unsupported non-standard supervisor-level extension 'sxmadeup'");
   EXPECT_EQ(
       toString(
           RISCVISAInfo::parseArchString("rv64g_xmadeup", true).takeError()),
       "unsupported non-standard user-level extension 'xmadeup'");
 }
 
 TEST(ParseArchString, IgnoresUnrecognizedExtensionNamesWithIgnoreUnknown) {
-  for (StringRef Input : {"rv32ib"}) {
+  for (StringRef Input : {"rv32ib", "rv32i_zmadeup", "rv64i_smadeup",
+                          "rv32i_sxmadeup", "rv64i_xmadeup"}) {
     auto MaybeISAInfo = RISCVISAInfo::parseArchString(Input, true, false, true);
     ASSERT_THAT_EXPECTED(MaybeISAInfo, Succeeded());
     RISCVISAInfo &Info = **MaybeISAInfo;
     RISCVISAInfo::OrderedExtensionMap Exts = Info.getExtensions();
     EXPECT_EQ(Exts.size(), 1UL);
     EXPECT_TRUE(Exts.at("i") == (RISCVExtensionInfo{"i", 2, 0}));
   }
-  // FIXME: These unrecognized extensions should be ignored just as in the
-  // case above. The below captures the current (incorrect) behaviour.
-  for (StringRef Input :
-       {"rv32i_zmadeup", "rv64i_smadeup", "rv32i_sxmadeup", "rv64i_xmadeup"}) {
-    auto MaybeISAInfo = RISCVISAInfo::parseArchString(Input, true, false, true);
-    EXPECT_THAT_EXPECTED(MaybeISAInfo, Failed());
-  }
 }
 
 TEST(ParseArchString, AcceptsVersionInLongOrShortForm) {
   for (StringRef Input : {"rv64i2", "rv64i2p0"}) {
     auto MaybeISAInfo = RISCVISAInfo::parseArchString(Input, true);
     ASSERT_THAT_EXPECTED(MaybeISAInfo, Succeeded());
     RISCVISAInfo::OrderedExtensionMap Exts = (*MaybeISAInfo)->getExtensions();
     EXPECT_TRUE(Exts.at("i") == (RISCVExtensionInfo{"i", 2, 0}));