[NFC][RISCV] rename findFirstNonVersionCharacter with findLastNonVersionCharacter

[craig.topper]

LGTM

[jrtc27]

llvm/lib/Support/RISCVISAInfo.cpp

179

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[BeMg]

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llvm/lib/Support/RISCVISAInfo.cpp

static const RISCVSupportedExtension SupportedExperimentalExtensions[] = {
     {"zvksh", RISCVExtensionVersion{0, 9}},
     {"zvkt", RISCVExtensionVersion{0, 9}},
 };
 
 static bool stripExperimentalPrefix(StringRef &Ext) {
   return Ext.consume_front("experimental-");
 }
 
-// This function finds the first character that doesn't belong to a version
+// This function finds the last character that doesn't belong to a version
 // (e.g. zba1p0 is extension 'zba' of version '1p0'). So the function will
 // consume [0-9]*p[0-9]* starting from the backward. An extension name will not
 // end with a digit or the letter 'p', so this function will parse correctly.
 // NOTE: This function is NOT able to take empty strings or strings that only
 // have version numbers and no extension name. It assumes the extension name
 // will be at least more than one character.
-static size_t findFirstNonVersionCharacter(StringRef Ext) {
+static size_t findLastNonVersionCharacter(StringRef Ext) {
   assert(!Ext.empty() &&
          "Already guarded by if-statement in ::parseArchString");
 
   int Pos = Ext.size() - 1;
   while (Pos > 0 && isDigit(Ext[Pos]))
     Pos--;
   if (Pos > 0 && Ext[Pos] == 'p' && isDigit(Ext[Pos - 1])) {
     Pos--;
RISCVISAInfo::parseArchString(StringRef Arch, bool EnableExperimentalExtension,
   if (Split.size() > 1 || Split[0] != "") {
     for (StringRef Ext : Split) {
       if (Ext.empty())
         return createStringError(errc::invalid_argument,
                                  "extension name missing after separator '_'");
 
       StringRef Type = getExtensionType(Ext);
       StringRef Desc = getExtensionTypeDesc(Ext);
-      auto Pos = findFirstNonVersionCharacter(Ext) + 1;
+      auto Pos = findLastNonVersionCharacter(Ext) + 1;
       StringRef Name(Ext.substr(0, Pos));
       StringRef Vers(Ext.substr(Pos));
 
       if (Type.empty()) {
         if (IgnoreUnknown)
           continue;
         return createStringError(errc::invalid_argument,
                                  "invalid extension prefix '" + Ext + "'");