[LTO] Use StringRef instead of C-style strings in setCodeGenDebugOptions

[chill]

Summary

Fixes an issue with missing nul-terminators and saves us some
string copying, compared to a version which would insert nul-terminators.

[thegameg]

Would it be cleaner to make setCodeGenDebugOptions take an ArrayRef<StringRef>?

[chill]

Yeah, I'd prefer that, but then I'm hesitant to change APIs.

[thegameg]

LGTM, thanks.

llvm/include/llvm/LTO/legacy/LTOCodeGenerator.h

struct LTOCodeGenerator {
   void addMustPreserveSymbol(StringRef Sym) { MustPreserveSymbols.insert(Sym); }
 
   /// Pass options to the driver and optimization passes.
   ///
   /// These options are not necessarily for debugging purpose (the function
   /// name is misleading).  This function should be called before
   /// LTOCodeGenerator::compilexxx(), and
   /// LTOCodeGenerator::writeMergedModules().
-  void setCodeGenDebugOptions(ArrayRef<const char *> Opts);
+  void setCodeGenDebugOptions(ArrayRef<StringRef> Opts);
 
   /// Parse the options set in setCodeGenDebugOptions.
   ///
   /// Like \a setCodeGenDebugOptions(), this must be called before
   /// LTOCodeGenerator::compilexxx() and
   /// LTOCodeGenerator::writeMergedModules().
   void parseCodeGenDebugOptions();
 

llvm/lib/LTO/LTOCodeGenerator.cpp

bool LTOCodeGenerator::compileOptimized(ArrayRef<raw_pwrite_stream *> Out) {
 
   reportAndResetTimings();
 
   finishOptimizationRemarks();
 
   return true;
 }
 
-void LTOCodeGenerator::setCodeGenDebugOptions(ArrayRef<const char *> Options) {
+void LTOCodeGenerator::setCodeGenDebugOptions(ArrayRef<StringRef> Options) {
   for (StringRef Option : Options)
-    CodegenOptions.push_back(std::string(Option));
+    CodegenOptions.push_back(Option.str());
 }
 
 void LTOCodeGenerator::parseCodeGenDebugOptions() {
   // if options were requested, set them
   if (!CodegenOptions.empty()) {
     // ParseCommandLineOptions() expects argv[0] to be program name.
     std::vector<const char *> CodegenArgv(1, "libLLVMLTO");
     for (std::string &Arg : CodegenOptions)

llvm/tools/lto/lto.cpp

 bool lto_codegen_compile_to_file(lto_code_gen_t cg, const char **name) {
   maybeParseOptions(cg);
   return !unwrap(cg)->compile_to_file(
       name, DisableVerify, DisableInline, DisableGVNLoadPRE,
       DisableLTOVectorization);
 }
 
 void lto_codegen_debug_options(lto_code_gen_t cg, const char *opt) {
-  std::vector<const char *> Options;
+  SmallVector<StringRef, 4> Options;
   for (std::pair<StringRef, StringRef> o = getToken(opt); !o.first.empty();
        o = getToken(o.second))
-    Options.push_back(o.first.data());
+    Options.push_back(o.first);
 
   unwrap(cg)->setCodeGenDebugOptions(Options);
 }
 
 void lto_codegen_debug_options_array(lto_code_gen_t cg,
                                      const char *const *options, int number) {
-  unwrap(cg)->setCodeGenDebugOptions(makeArrayRef(options, number));
+  SmallVector<StringRef, 4> Options;
+  for (int i = 0; i < number; ++i)
+    Options.push_back(options[i]);
+  unwrap(cg)->setCodeGenDebugOptions(makeArrayRef(Options));
 }
 
 unsigned int lto_api_version() { return LTO_API_VERSION; }
 
 void lto_codegen_set_should_internalize(lto_code_gen_t cg,
                                         bool ShouldInternalize) {
   unwrap(cg)->setShouldInternalize(ShouldInternalize);
 }