Use feature to allow/disallow experimental extensions.

Author: Yeting Kuo

clang/lib/Driver/ToolChains/Clang.cpp

@@ -8449,11 +8449,6 @@ void ClangAs::AddRISCVTargetArgs(const ArgList &Args,
       CmdArgs.push_back("-mllvm");
       CmdArgs.push_back("-riscv-add-build-attributes");
   }
-
-  if (!Args.hasArg(options::OPT_menable_experimental_extensions)) {
-    CmdArgs.push_back("-mllvm");
-    CmdArgs.push_back("-riscv-disable-experimental-ext");
-  }
 }
 
 void ClangAs::ConstructJob(Compilation &C, const JobAction &JA,

clang/test/Driver/riscv-option-arch.c

@@ -0,0 +1,7 @@
+// RUN: %clang --target=riscv64 -menable-experimental-extensions -c -o /dev/null %s
+// RUN: ! %clang --target=riscv64 -c -o /dev/null %s 2>&1 | FileCheck -check-prefixes=CHECK-ERR %s
+
+void foo() {
+  asm volatile (".option arch, +zicfiss");
+  // CHECK-ERR: Unexpected experimental extensions.
+}

llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp

@@ -51,10 +51,6 @@ STATISTIC(RISCVNumInstrsCompressed,
 
 static cl::opt<bool> AddBuildAttributes("riscv-add-build-attributes",
                                         cl::init(false));
-static cl::opt<bool>
-    DisableExperimentalExtension("riscv-disable-experimental-ext",
-                                 cl::init(false));
-
 namespace llvm {
 extern const SubtargetFeatureKV RISCVFeatureKV[RISCV::NumSubtargetFeatures];
 } // namespace llvm
@@ -87,6 +83,9 @@ class RISCVAsmParser : public MCTargetAsmParser {
   SMLoc getLoc() const { return getParser().getTok().getLoc(); }
   bool isRV64() const { return getSTI().hasFeature(RISCV::Feature64Bit); }
   bool isRVE() const { return getSTI().hasFeature(RISCV::FeatureStdExtE); }
+  bool enableExperimentalExtension() const {
+    return getSTI().hasFeature(RISCV::Experimental);
+  }
 
   RISCVTargetStreamer &getTargetStreamer() {
     assert(getParser().getStreamer().getTargetStreamer() &&
@@ -2828,7 +2827,7 @@ bool RISCVAsmParser::parseDirectiveOption() {
       }
 
       std::string Feature = RISCVISAInfo::getTargetFeatureForExtension(Arch);
-      if (DisableExperimentalExtension &&
+      if (!enableExperimentalExtension() &&
           StringRef(Feature).starts_with("experimental-"))
         return Error(Loc, "Unexpected experimental extensions.");
       auto Ext = llvm::lower_bound(RISCVFeatureKV, Feature);

llvm/test/MC/RISCV/option-arch.s

@@ -1,6 +1,6 @@
-# RUN: llvm-mc -triple riscv32 -show-encoding < %s \
+# RUN: llvm-mc -triple riscv32 -mattr=+experimental -show-encoding < %s \
 # RUN:   | FileCheck -check-prefixes=CHECK %s
-# RUN: llvm-mc -triple riscv32 -filetype=obj < %s \
+# RUN: llvm-mc -triple riscv32 -mattr=+experimental -filetype=obj < %s \
 # RUN:   | llvm-objdump  --triple=riscv32 --mattr=+c,+m,+a,+f,+zba,+experimental-zicfiss -d -M no-aliases - \
 # RUN:   | FileCheck -check-prefixes=CHECK-INST %s