[Clang][RISCV] Recognize unsupport target feature by supporting isValidFeatureName (#106495)

This patch makes unsupported target attributes emit a warning and ignore
the target attribute during semantic checks. The changes include:

1. Adding the RISCVTargetInfo::isValidFeatureName function.
2. Rejecting non-full-arch strings in the handleFullArchString function.
3. Adding test cases to demonstrate the warning behavior.

clang/lib/Basic/Targets/RISCV.cpp

@@ -388,7 +388,7 @@ static void handleFullArchString(StringRef FullArchStr,
       FullArchStr, /* EnableExperimentalExtension */ true);
   if (llvm::errorToBool(RII.takeError())) {
     // Forward the invalid FullArchStr.
-    Features.push_back("+" + FullArchStr.str());
+    Features.push_back(FullArchStr.str());
   } else {
     // Append a full list of features, including any negative extensions so that
     // we override the CPU's features.
@@ -478,3 +478,7 @@ bool RISCVTargetInfo::validateCpuSupports(StringRef Feature) const {
   // __riscv_feature_bits structure.
   return -1 != llvm::RISCVISAInfo::getRISCVFeaturesBitsInfo(Feature).second;
 }
+
+bool RISCVTargetInfo::isValidFeatureName(StringRef Name) const {
+  return llvm::RISCVISAInfo::isSupportedExtensionFeature(Name);
+}

clang/lib/Basic/Targets/RISCV.h

@@ -130,6 +130,7 @@ public:
   bool supportsCpuSupports() const override { return getTriple().isOSLinux(); }
   bool supportsCpuInit() const override { return getTriple().isOSLinux(); }
   bool validateCpuSupports(StringRef Feature) const override;
+  bool isValidFeatureName(StringRef Name) const override;
 };
 class LLVM_LIBRARY_VISIBILITY RISCV32TargetInfo : public RISCVTargetInfo {
 public:

clang/lib/Sema/SemaDeclAttr.cpp

@@ -2993,10 +2993,17 @@ bool Sema::checkTargetAttr(SourceLocation LiteralLoc, StringRef AttrStr) {
     return Diag(LiteralLoc, diag::warn_unsupported_target_attribute)
            << Unknown << Tune << ParsedAttrs.Tune << Target;
 
-  if (Context.getTargetInfo().getTriple().isRISCV() &&
-      ParsedAttrs.Duplicate != "")
-    return Diag(LiteralLoc, diag::err_duplicate_target_attribute)
-           << Duplicate << None << ParsedAttrs.Duplicate << Target;
+  if (Context.getTargetInfo().getTriple().isRISCV()) {
+    if (ParsedAttrs.Duplicate != "")
+      return Diag(LiteralLoc, diag::err_duplicate_target_attribute)
+             << Duplicate << None << ParsedAttrs.Duplicate << Target;
+    for (const auto &Feature : ParsedAttrs.Features) {
+      StringRef CurFeature = Feature;
+      if (!CurFeature.starts_with('+') && !CurFeature.starts_with('-'))
+        return Diag(LiteralLoc, diag::warn_unsupported_target_attribute)
+               << Unsupported << None << AttrStr << Target;
+    }
+  }
 
   if (ParsedAttrs.Duplicate != "")
     return Diag(LiteralLoc, diag::warn_unsupported_target_attribute)

clang/test/Sema/attr-target-riscv.c

@@ -4,3 +4,15 @@
 int __attribute__((target("arch=rv64g"))) foo(void) { return 0; }
 //expected-error@+1 {{redefinition of 'foo'}}
 int __attribute__((target("arch=rv64gc"))) foo(void) { return 0; }
+
+//expected-warning@+1 {{unsupported 'notafeature' in the 'target' attribute string; 'target' attribute ignored}}
+int __attribute__((target("arch=+notafeature"))) UnsupportFeature(void) { return 0; }
+
+//expected-warning@+1 {{unsupported 'notafeature' in the 'target' attribute string; 'target' attribute ignored}}
+int __attribute__((target("arch=-notafeature"))) UnsupportNegativeFeature(void) { return 0; }
+
+//expected-warning@+1 {{unsupported 'arch=+zba,zbb' in the 'target' attribute string; 'target' attribute ignored}}
+int __attribute__((target("arch=+zba,zbb"))) WithoutPlus(void) { return 0; }
+
+//expected-warning@+1 {{unsupported 'arch=zba' in the 'target' attribute string; 'target' attribute ignored}}
+int __attribute__((target("arch=zba"))) WithoutPlus2(void) { return 0; }