[llvm-stress] Remove dependency to legacy pass manager

[bjope]

Summary

This patch removes the dependency to the legacy pass manager when
building llvm-stress.

Instead of setting up a pass manager at all we just run verifyModule()
to check that the generated IR satisfies the verifier, and then
we use Module::print() to output the IR. No need to setup passes and
populating a pass manager since we aren't doing anything more fancy
than that.

[aeubanks]

llvm/tools/llvm-stress/llvm-stress.cpp

766

can't we just WriteBitcodeToFile without a pass manager?

[bjope]

llvm/tools/llvm-stress/llvm-stress.cpp

766

Oh, yes. Why didn't I go all the way like that. No need to create the PrintModulePass just to do the WriteBircodeToFile. It should be possible to just call that helper directly. I'll try to update the patch that way.

[bjope]

Now using M->print() directly to output the IR.

[aeubanks]

description needs updating, otherwise lgtm

llvm/tools/llvm-stress/llvm-stress.cpp

 #include "llvm/ADT/Twine.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/CallingConv.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GlobalValue.h"
-#include "llvm/IR/IRPrintingPasses.h"
 #include "llvm/IR/InstrTypes.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/LLVMContext.h"
-#include "llvm/IR/LegacyPassManager.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Type.h"
 #include "llvm/IR/Value.h"
 #include "llvm/IR/Verifier.h"
-#include "llvm/Pass.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/InitLLVM.h"
 #include "llvm/Support/ToolOutputFile.h"
 #include "llvm/Support/WithColor.h"
 #include "llvm/Support/raw_ostream.h"
int main(int argc, char **argv) {
 
   std::error_code EC;
   Out.reset(new ToolOutputFile(OutputFilename, EC, sys::fs::OF_None));
   if (EC) {
     errs() << EC.message() << '\n';
     return 1;
   }
 
-  legacy::PassManager Passes;
-  Passes.add(createVerifierPass());
-  Passes.add(createPrintModulePass(Out->os()));
-  Passes.run(*M.get());
+  // Check that the generated module is accepted by the verifier.
+  if (verifyModule(*M.get(), &Out->os()))
+    report_fatal_error("Broken module found, compilation aborted!");
+
+  // Output textual IR.
+  M->print(Out->os(), nullptr);
+
   Out->keep();
 
   return 0;
 }