[RISCV] Add getExtensionSerial

[BeMg]

Summary

Provide a unique number for extension, and use it to implement multiVersionSortPriority.

llvm/include/llvm/Support/RISCVISAInfo.h

public:
   static bool isSupportedExtensionFeature(StringRef Ext);
   static bool isSupportedExtension(StringRef Ext);
   static bool isSupportedExtensionWithVersion(StringRef Ext);
   static bool isSupportedExtension(StringRef Ext, unsigned MajorVersion,
                                    unsigned MinorVersion);
   static llvm::Expected<std::unique_ptr<RISCVISAInfo>>
   postProcessAndChecking(std::unique_ptr<RISCVISAInfo> &&ISAInfo);
   static std::string getTargetFeatureForExtension(StringRef Ext);
+  static unsigned getExtensionSerial(StringRef ExtName);
 
 private:
   RISCVISAInfo(unsigned XLen)
       : XLen(XLen), FLen(0), MinVLen(0), MaxELen(0), MaxELenFp(0) {}
 
   unsigned XLen;
   unsigned FLen;
   unsigned MinVLen;

llvm/lib/Support/RISCVISAInfo.cpp

if (Pos != Ext.size() && !isSupportedExtensionWithVersion(Ext))
     return std::string();
 
   if (!isSupportedExtension(Name))
     return std::string();
 
   return isExperimentalExtension(Name) ? "experimental-" + Name.str()
                                        : Name.str();
 }
+
+
+
+unsigned RISCVISAInfo::getExtensionSerial(StringRef ExtName) {
+  verifyTables();
+
+  unsigned Offset = 1;
+  if (stripExperimentalPrefix(ExtName))
+    Offset += sizeof(SupportedExtensions) / sizeof(SupportedExtensions[0]);
+
+  for (auto ExtInfo : {ArrayRef(SupportedExtensions),
+                       ArrayRef(SupportedExperimentalExtensions)}) {
+    auto I = llvm::lower_bound(ExtInfo, ExtName, LessExtName());
+    if (I != ExtInfo.end() && I->Name == ExtName)
+      return (I - ExtInfo.begin()) + Offset;
+  }
+
+  return 0;
+}

llvm/unittests/Support/RISCVISAInfoTest.cpp

TEST(getTargetFeatureForExtension, RetrieveTargetFeatureFromOneExt) {
   EXPECT_EQ(RISCVISAInfo::getTargetFeatureForExtension("zicond"),
             "experimental-zicond");
   EXPECT_EQ(RISCVISAInfo::getTargetFeatureForExtension("zihintntl1234p4321"),
             "");
   EXPECT_EQ(RISCVISAInfo::getTargetFeatureForExtension("zfoo"), "");
   EXPECT_EQ(RISCVISAInfo::getTargetFeatureForExtension(""), "");
   EXPECT_EQ(RISCVISAInfo::getTargetFeatureForExtension("zbbzihintntl"), "");
 }
+
+TEST(getExtensionSerial, RetrieveAUniqueNumberForExt) {
+  EXPECT_EQ(RISCVISAInfo::getExtensionSerial("f"), 5U);
+  EXPECT_EQ(RISCVISAInfo::getExtensionSerial("a"), 1U);
+  EXPECT_EQ(RISCVISAInfo::getExtensionSerial("foo"), 0U);
+  EXPECT_EQ(RISCVISAInfo::getExtensionSerial("experimental-zicond"), 97U);
+}