[RISCV] Make RISCVISAInfo::toFeatureVector ignore unsupported extensions

[asb]

Summary

parseNormalizedArchString adds a code path that creates a RISCVISAInfo including extensions that may not be supported by LLVM (rather than erroring or just ignoring them). Therefore, toFeatureVector needs to check the extension is supported in order to avoid creating unrecognised feature strings.

This change shouldn't impact any code paths used outside of test code, but this will be relied upon by the next patch which moves llvm-objdump and related tools over to using parseNormalizedArchString.

llvm/lib/Support/RISCVISAInfo.cpp

 }
 
 std::vector<std::string> RISCVISAInfo::toFeatureVector() const {
   std::vector<std::string> FeatureVector;
   for (auto const &Ext : Exts) {
     std::string ExtName = Ext.first;
     if (ExtName == "i") // i is not recognized in clang -cc1
       continue;
+    if (!isSupportedExtension(ExtName))
+      continue;
     std::string Feature = isExperimentalExtension(ExtName)
                               ? "+experimental-" + ExtName
                               : "+" + ExtName;
     FeatureVector.push_back(Feature);
   }
   return FeatureVector;
 }
 

llvm/unittests/Support/RISCVISAInfoTest.cpp

EXPECT_THAT((*MaybeISAInfo1)->toFeatureVector(),
               ElementsAre("+m", "+experimental-zihintntl"));
 
   auto MaybeISAInfo2 = RISCVISAInfo::parseArchString(
       "rv32e_zihintntl_xventanacondops", true, false);
   ASSERT_THAT_EXPECTED(MaybeISAInfo2, Succeeded());
   EXPECT_THAT((*MaybeISAInfo2)->toFeatureVector(),
               ElementsAre("+e", "+experimental-zihintntl", "+xventanacondops"));
 }
+
+TEST(ToFeatureVector, UnsupportedExtensionsAreDropped) {
+  auto MaybeISAInfo =
+      RISCVISAInfo::parseNormalizedArchString("rv64i2p0_m2p0_xmadeup1p0");
+  ASSERT_THAT_EXPECTED(MaybeISAInfo, Succeeded());
+  EXPECT_THAT((*MaybeISAInfo)->toFeatureVector(), ElementsAre("+m"));
+}