[llvm-reduce] Skip dso_local reduction step that results in invalid IR

[arichardson]

Summary

Trying to call setDSOLocal(false) on a GlobalValue that is implicitly
dso_local results in the following module verifier error:

• WARNING | reduction resulted in invalid module, skipping GlobalValue with local linkage or non-default visibility must be dso_local!

Since this will never result in a valid test case reduction, skip it to avoid
unncessary work and lots of WARNING messages.

[fhahn]

Could you add a test for this?

[arichardson]

In D99943#2670827, @fhahn wrote:

Could you add a test for this?

Should I add a new test or is modifying the test from D98673 sufficient?

[fhahn]

In D99943#2670840, @arichardson wrote:

In D99943#2670827, @fhahn wrote:

Could you add a test for this?

Should I add a new test or is modifying the test from D98673 sufficient?

I'd go with whatever is easiest.

[aeubanks]

llvm/tools/llvm-reduce/deltas/ReduceGlobalValues.cpp

40

This should also check GV.isImplicitDSOLocal

[arichardson]

Superseded by D101279

llvm/tools/llvm-reduce/deltas/ReduceGlobalValues.cpp

 
 /// Sets dso_local to false for all global values.
 static void extractGVsFromModule(std::vector<Chunk> ChunksToKeep,
                                  Module *Program) {
   Oracle O(ChunksToKeep);
 
   // remove dso_local from global values
   for (auto &GV : Program->global_values())
-    if (GV.isDSOLocal() && !O.shouldKeep()) {
+    if (GV.isDSOLocal() && !GV.isImplicitDSOLocal() && !O.shouldKeep()) {
       GV.setDSOLocal(false);
     }
 }
 
 /// Counts the amount of global values with dso_local and displays their
 /// respective name & index
 static int countGVs(Module *Program) {
   // TODO: Silence index with --quiet flag
   outs() << "----------------------------\n";
   outs() << "GlobalValue Index Reference:\n";
   int GVCount = 0;
   for (auto &GV : Program->global_values())
     if (GV.isDSOLocal())
       outs() << "\t" << ++GVCount << ": " << GV.getName() << "\n";
   outs() << "----------------------------\n";
   return GVCount;
 }
 
 void llvm::reduceGlobalValuesDeltaPass(TestRunner &Test) {
   outs() << "*** Reducing GlobalValues...\n";
   int GVCount = countGVs(Test.getProgram());
   runDeltaPass(Test, GVCount, extractGVsFromModule);
 }