[NewPM] teach -passes= to emit meaningful error messages

All the PassBuilder::parse interfaces now return descriptive StringError
instead of a plain bool. It allows to make -passes/aa-pipeline parsing
errors context-specific and thus less confusing.

TODO: ideally we should also make suggestions for misspelled pass names,
but that requires some extensions to PassBuilder.

Reviewed By: philip.pfaffe, chandlerc
Differential Revision: https://reviews.llvm.org/D53246

llvm-svn: 344685

1 files changed, 6 insertions, 5 deletions

diff --git a/llvm/tools/llvm-opt-fuzzer/llvm-opt-fuzzer.cpp b/llvm/tools/llvm-opt-fuzzer/llvm-opt-fuzzer.cpp
index 98d5428ddd1..57e75b1db9e 100644
--- a/llvm/tools/llvm-opt-fuzzer/llvm-opt-fuzzer.cpp
+++ b/llvm/tools/llvm-opt-fuzzer/llvm-opt-fuzzer.cpp
@@ -144,9 +144,10 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
   PB.registerLoopAnalyses(LAM);
   PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
 
-  bool Ok = PB.parsePassPipeline(MPM, PassPipeline, false, false);
-  assert(Ok && "Should have been checked during fuzzer initialization");
-  (void)Ok; // silence unused variable warning on release builds
+  auto Err = PB.parsePassPipeline(MPM, PassPipeline, false, false);
+  assert(!Err && "Should have been checked during fuzzer initialization");
+  // Only fail with assert above, otherwise ignore the parsing error.
+  consumeError(std::move(Err));
 
   // Run passes which we need to test
   //
@@ -235,8 +236,8 @@ extern "C" LLVM_ATTRIBUTE_USED int LLVMFuzzerInitialize(
 
   PassBuilder PB(TM.get());
   ModulePassManager MPM;
-  if (!PB.parsePassPipeline(MPM, PassPipeline, false, false)) {
-    errs() << *argv[0] << ": can't parse pass pipeline\n";
+  if (auto Err = PB.parsePassPipeline(MPM, PassPipeline, false, false)) {
+    errs() << *argv[0] << ": " << toString(std::move(Err)) << "\n";
     exit(1);
   }