Replace usage of StringRef::find_last_of with a string literal of size one by the equivalent char literal

Author: serge-sans-paille

clang/lib/Driver/ToolChains/ZOS.cpp

@@ -143,7 +143,7 @@ void zos::Linker::ConstructJob(Compilation &C, const JobAction &JA,
     StringRef OutputName = Output.getFilename();
     // Strip away the last file suffix in presence from output name and add
     // a new .x suffix.
-    size_t Suffix = OutputName.find_last_of(".");
+    size_t Suffix = OutputName.find_last_of('.');
     const char *SideDeckName =
         Args.MakeArgString(OutputName.substr(0, Suffix) + ".x");
     CmdArgs.push_back("-x");

llvm/lib/Target/AMDGPU/AMDGPUPrintfRuntimeBinding.cpp

@@ -102,7 +102,7 @@ void AMDGPUPrintfRuntimeBindingImpl::getConversionSpecifiers(
     bool ArgDump = false;
     StringRef CurFmt = Fmt.substr(PrevFmtSpecifierIdx,
                                   CurFmtSpecifierIdx - PrevFmtSpecifierIdx);
-    size_t pTag = CurFmt.find_last_of("%");
+    size_t pTag = CurFmt.find_last_of('%');
     if (pTag != StringRef::npos) {
       ArgDump = true;
       while (pTag && CurFmt[--pTag] == '%') {

llvm/lib/Target/SPIRV/SPIRVBuiltins.cpp

@@ -163,7 +163,7 @@ lookupBuiltin(StringRef DemangledCall,
   // the information after angle brackets and return type removed.
   if (BuiltinName.find('<') && BuiltinName.back() == '>') {
     BuiltinName = BuiltinName.substr(0, BuiltinName.find('<'));
-    BuiltinName = BuiltinName.substr(BuiltinName.find_last_of(" ") + 1);
+    BuiltinName = BuiltinName.substr(BuiltinName.find_last_of(' ') + 1);
   }
 
   // Check if the extracted name begins with "__spirv_ImageSampleExplicitLod"

mlir/lib/Tools/lsp-server-support/SourceMgrUtils.cpp

@@ -83,7 +83,7 @@ lsp::extractSourceDocComment(llvm::SourceMgr &sourceMgr, SMLoc loc) {
 
   // Pop the last line from the buffer string.
   auto popLastLine = [&]() -> std::optional<StringRef> {
-    size_t newlineOffset = buffer.find_last_of("\n");
+    size_t newlineOffset = buffer.find_last_of('\n');
     if (newlineOffset == StringRef::npos)
       return std::nullopt;
     StringRef lastLine = buffer.drop_front(newlineOffset).trim();