[llvm-dwp] Add a command line option to set the target triple

[pfaffe]

Summary

The llvm-dwp tool hard-codes the target triple to x86. Instead, add a command
line option for overriding the default triple to support alternative targets
such as WebAssembly as well.

[dblaikie]

Could the target triple be identified from one of the input files instead? (in any case, this'll need test coverage)

[pfaffe]

Read triple from first dwo file instead of from command line and add a test.

[dblaikie]

Code change looks good - test might be able to be tweaked a bit before committing.

llvm/test/tools/llvm-dwp/WebAssembly/simple.test

1 ↗

(On Diff #316390)

Could the wasm.dwo file be written in assembly (that's more the style used these days, compared to when I wrote the original dwp tests) and assembled with llvm-mc? (this .test file could be the assembly .s file instead - self-describing/standalone in one file rather than an opaque binary beside this .test file that doesn't describe its inputs)

[pfaffe]

Replace binary test with an assembly test.

[pfaffe]

Rebase and improve testcase: The file can just be empty.

[pfaffe]

Restore changes lost in previous patchset.

[dblaikie]

Looks good

llvm/tools/llvm-dwp/llvm-dwp.cpp

static cl::list<std::string> ExecFilenames(
     cl::desc("Specify the executable/library files to get the list of *.dwo from"),
     cl::value_desc("filename"), cl::cat(DwpCategory));
 
 static cl::opt<std::string> OutputFilename(cl::Required, "o",
                                            cl::desc("Specify the output file."),
                                            cl::value_desc("filename"),
                                            cl::cat(DwpCategory));
 
+static cl::opt<std::string>
+    TargetTriple("triple", cl::desc("Override target triple for module"),
+                 cl::init("x86_64-linux-gnu"));
+
 static void writeStringsAndOffsets(MCStreamer &Out, DWPStringPool &Strings,
                                    MCSection *StrOffsetSection,
                                    StringRef CurStrSection,
                                    StringRef CurStrOffsetSection) {
   // Could possibly produce an error or warning if one of these was non-null but
   // the other was null.
   if (CurStrSection.empty() || CurStrOffsetSection.empty())
     return;
int main(int argc, char **argv) {
   llvm::InitializeAllTargetInfos();
   llvm::InitializeAllTargetMCs();
   llvm::InitializeAllTargets();
   llvm::InitializeAllAsmPrinters();
 
   std::string ErrorStr;
   StringRef Context = "dwarf streamer init";
 
-  Triple TheTriple("x86_64-linux-gnu");
+  Triple TheTriple(TargetTriple);
 
   // Get the target.
   const Target *TheTarget =
       TargetRegistry::lookupTarget("", TheTriple, ErrorStr);
   if (!TheTarget)
     return error(ErrorStr, Context);
   std::string TripleName = TheTriple.getTriple();