[RISCV] Fix RISCVTargetInfo::initFeatureMap, add non-ISA features back after implication

[eopXD]

Summary

Previously D113336 makes RISCVTargetInfo::initFeatureMap return the results
processed by RISCVISAInfo, which only consists of ISA features and misses
non-ISA features like relax and save-restore.

This patch fixes the problem.

[eopXD]

Add testcase.

[junparser]

LGTM, thanks for the fix.

[rogfer01]

clang/test/Driver/riscv-default-features.c

4 ↗

(On Diff #408325)

I think we may be missing are missing a RUN line for this case, right?

[eopXD]

clang/test/Driver/riscv-default-features.c

4 ↗

(On Diff #408325)

Created patch D120297, thanks!

[arichardson]

I just noticed that target features (e.g. -mrelax) are broken in all LLVM 14 releases due to D113336 . This should have been cherry-picked back tot the release branch, but it's too late now. In the future please ensure that important fixes such as this one end up on the release branch as well.

[asb]

In D119541#3940597, @arichardson wrote:

I just noticed that target features (e.g. -mrelax) are broken in all LLVM 14 releases due to D113336 . This should have been cherry-picked back tot the release branch, but it's too late now. In the future please ensure that important fixes such as this one end up on the release branch as well.

Thanks for flagging that this was missed - definitely a collective failure here for us to recognise this was fixing an important bug in a shipping release. We'll try harder to keep in mind the possibility of cherry-picking into point releases in the future.

clang/lib/Basic/Targets/RISCV.cpp

if (!ParseResult) {
     llvm::raw_string_ostream OutputErrMsg(Buffer);
     handleAllErrors(ParseResult.takeError(), [&](llvm::StringError &ErrMsg) {
       OutputErrMsg << ErrMsg.getMessage();
     });
     Diags.Report(diag::err_invalid_feature_combination) << OutputErrMsg.str();
     return false;
   }
 
-  return TargetInfo::initFeatureMap(Features, Diags, CPU,
-                                    (*ParseResult)->toFeatureVector());
+  // RISCVISAInfo makes implications for ISA features
+  std::vector<std::string> ImpliedFeatures = (*ParseResult)->toFeatureVector();
+  // Add non-ISA features like `relax` and `save-restore` back
+  for (std::string Feature : FeaturesVec) {
+    if (std::find(begin(ImpliedFeatures), end(ImpliedFeatures), Feature) ==
+        end(ImpliedFeatures))
+      ImpliedFeatures.push_back(Feature);
+  }
+
+  return TargetInfo::initFeatureMap(Features, Diags, CPU, ImpliedFeatures);
 }
 
 /// Return true if has this feature, need to sync with handleTargetFeatures.
 bool RISCVTargetInfo::hasFeature(StringRef Feature) const {
   bool Is64Bit = getTriple().getArch() == llvm::Triple::riscv64;
   auto Result = llvm::StringSwitch<Optional<bool>>(Feature)
                     .Case("riscv", true)
                     .Case("riscv32", !Is64Bit)