[mlir][gpu] Fix option parsing in `TargetOptions`

[fmorac]

Summary

TargetOptions includes a field for passing additional command line options to
the GPU compilation process. This field is typically used during the 'gpu-module-to-binary`
pass:

--gpu-module-to-binary=opts="-v -c"

The problem is that tokenizeCmdOptions receives the quoted string, which produces an
incorrect tokenization for "-v -c". This patch removes quotes, fixing this issue.

[bondhugula]

mlir/lib/Dialect/GPU/IR/GPUDialect.cpp

2010

opts.size() -> !opts.empty()

2010–2013

Need a code comment.

[fmorac]

Addressed comments.

mlir/lib/Dialect/GPU/IR/GPUDialect.cpp

 ArrayRef<std::string> TargetOptions::getLinkFiles() const { return linkFiles; }
 
 StringRef TargetOptions::getCmdOptions() const { return cmdOptions; }
 
 std::pair<llvm::BumpPtrAllocator, SmallVector<const char *>>
 TargetOptions::tokenizeCmdOptions() const {
   std::pair<llvm::BumpPtrAllocator, SmallVector<const char *>> options;
   llvm::StringSaver stringSaver(options.first);
+  StringRef opts = cmdOptions;
+  // For a correct tokenization of the command line options `opts` must be
+  // unquoted, otherwise the tokenization function returns a single string: the
+  // unquoted `cmdOptions` -which is not the desired behavior.
+  // Remove any quotes if they are at the beginning and end of the string:
+  if (!opts.empty() && opts.front() == '"' && opts.back() == '"')
+    opts.consume_front("\""), opts.consume_back("\"");
+  if (!opts.empty() && opts.front() == '\'' && opts.back() == '\'')
+    opts.consume_front("'"), opts.consume_back("'");
 #ifdef _WIN32
-  llvm::cl::TokenizeWindowsCommandLine(cmdOptions, stringSaver, options.second,
+  llvm::cl::TokenizeWindowsCommandLine(opts, stringSaver, options.second,
                                        /*MarkEOLs=*/false);
 #else
-  llvm::cl::TokenizeGNUCommandLine(cmdOptions, stringSaver, options.second,
+  llvm::cl::TokenizeGNUCommandLine(opts, stringSaver, options.second,
                                    /*MarkEOLs=*/false);
 #endif // _WIN32
   return options;
 }
 
 TargetOptions::CompilationTarget TargetOptions::getCompilationTarget() const {
   return compilationTarget;
 }