[RISCV][TableGen] Get right experimental extension name

We should remove the `experimental-` prefix when printing march
string.

We didn't meet this problem because there is no processor containing
experimental extensions.

Reviewers: fpetrogalli, asb, topperc

Reviewed By: topperc, asb

Pull Request: #90185

Author: wangpc-pp

llvm/test/TableGen/riscv-target-def.td

@@ -83,13 +83,15 @@ def ROCKET_RV32 : RISCVProcessorModel<"rocket-rv32",
                                        FeatureStdExtI,
                                        FeatureStdExtZifencei,
                                        FeatureStdExtZicsr,
+                                       FeatureStdExtZidummy,
                                        FeatureDummy]>;
 def ROCKET_RV64 : RISCVProcessorModel<"rocket-rv64",
                                       NoSchedModel,
                                       [Feature64Bit,
                                        FeatureStdExtI,
                                        FeatureStdExtZifencei,
                                        FeatureStdExtZicsr,
+                                       FeatureStdExtZidummy,
                                        FeatureDummy]>;
 def ROCKET : RISCVTuneProcessorModel<"rocket",
                                      NoSchedModel>;
@@ -125,8 +127,8 @@ def ROCKET : RISCVTuneProcessorModel<"rocket",
 
 // CHECK:      PROC(GENERIC_RV32, {"generic-rv32"}, {"rv32i2p1"}, 0)
 // CHECK-NEXT: PROC(GENERIC_RV64, {"generic-rv64"}, {"rv64i2p1"}, 0)
-// CHECK-NEXT: PROC(ROCKET_RV32, {"rocket-rv32"}, {"rv32i2p1_zicsr2p0_zifencei2p0"}, 0)
-// CHECK-NEXT: PROC(ROCKET_RV64, {"rocket-rv64"}, {"rv64i2p1_zicsr2p0_zifencei2p0"}, 0)
+// CHECK-NEXT: PROC(ROCKET_RV32, {"rocket-rv32"}, {"rv32i2p1_zicsr2p0_zidummy0p1_zifencei2p0"}, 0)
+// CHECK-NEXT: PROC(ROCKET_RV64, {"rocket-rv64"}, {"rv64i2p1_zicsr2p0_zidummy0p1_zifencei2p0"}, 0)
 
 // CHECK: #undef PROC
 

llvm/utils/TableGen/RISCVTargetDefEmitter.cpp

@@ -95,7 +95,7 @@ static void printMArch(raw_ostream &OS, const Record &Rec) {
 
   // Convert features to FeatureVector.
   for (auto *Feature : Rec.getValueAsListOfDefs("Features")) {
-    StringRef FeatureName = Feature->getValueAsString("Name");
+    StringRef FeatureName = getExtensionName(Feature);
     if (Feature->isSubClassOf("RISCVExtension")) {
       unsigned Major = Feature->getValueAsInt("MajorVersion");
       unsigned Minor = Feature->getValueAsInt("MinorVersion");