[StandardInstrumentations] Add option to dump IR to a file on crash

[aeubanks]

Summary

We already have -print-on-crash which dumps the IR to stderr on a crash, but it's more useful to dump to a file.

Introduce -print-on-crash-path to dump the IR to a file.

Making -print-on-crash a string option is confusing if you only pass -print-on-crash and it swallows up the next command line arg, which is why this is a new option.

Perhaps we could retire the dump to stderr version if people don't use it, but not sure how much people find that useful.

[hans]

llvm/lib/Passes/StandardInstrumentations.cpp

101

How about -print-on-crash-file and PrintOnCrashFile instead?

[jamieschmeiser]

llvm/lib/Passes/StandardInstrumentations.cpp

2228

You have removed the test on CrashReporter, which prevents multiple reporters. Now, a subsequent one will replace previous reporters. Is this intentional? I think the replaced ones will still be registered with the signal handler.

[aeubanks]

add back unintentionally removed condition

[jamieschmeiser]

LGTM

llvm/lib/Passes/StandardInstrumentations.cpp

 
 // An option that determines where the generated website file (named
 // passes.html) and the associated pdf files (named diff_*.pdf) are saved.
 static cl::opt<std::string> DotCfgDir(
     "dot-cfg-dir",
     cl::desc("Generate dot files into specified directory for changed IRs"),
     cl::Hidden, cl::init("./"));
 
-// An option to print the IR that was being processed when a pass crashes.
-static cl::opt<bool>
-    PrintCrashIR("print-on-crash",
-                 cl::desc("Print the last form of the IR before crash"),
-                 cl::Hidden);
+// Options to print the IR that was being processed when a pass crashes.
+static cl::opt<std::string> PrintOnCrashPath(
+    "print-on-crash-path",
+    cl::desc("Print the last form of the IR before crash to a file"),
+    cl::Hidden);
+
+static cl::opt<bool> PrintOnCrash(
+    "print-on-crash",
+    cl::desc("Print the last form of the IR before crash (use -print-on-crash-path to dump to a file)"),
 
 static cl::opt<std::string> OptBisectPrintIRPath(
     "opt-bisect-print-ir-path",
     cl::desc("Print IR to path when opt-bisect-limit is reached"), cl::Hidden);
 
 namespace {
 
 // An option for specifying an executable that will be called with the IR
: PrintPass(DebugLogging, PrintPassOpts),
                        PrintChanged == ChangePrinter::ColourDiffVerbose ||
                            PrintChanged == ChangePrinter::ColourDiffQuiet),
       WebsiteChangeReporter(PrintChanged == ChangePrinter::DotCfgVerbose),
       Verify(DebugLogging), VerifyEach(VerifyEach) {}
 
 PrintCrashIRInstrumentation *PrintCrashIRInstrumentation::CrashReporter =
     nullptr;
 
-void PrintCrashIRInstrumentation::reportCrashIR() { dbgs() << SavedIR; }
+void PrintCrashIRInstrumentation::reportCrashIR() {
+  if (!PrintOnCrashPath.empty()) {
+    std::error_code EC;
+    raw_fd_ostream Out(PrintOnCrashPath, EC);
+    if (EC)
+      report_fatal_error(errorCodeToError(EC));
+    Out << SavedIR;
+  } else {
+    dbgs() << SavedIR;
+  }
+}
 
 void PrintCrashIRInstrumentation::SignalHandler(void *) {
   // Called by signal handlers so do not lock here
   // Is the PrintCrashIRInstrumentation still alive?
   if (!CrashReporter)
     return;
 
-  assert(PrintCrashIR && "Did not expect to get here without option set.");
+  assert((PrintOnCrash || !PrintOnCrashPath.empty()) &&
+         "Did not expect to get here without option set.");
   CrashReporter->reportCrashIR();
 }
 
 PrintCrashIRInstrumentation::~PrintCrashIRInstrumentation() {
   if (!CrashReporter)
     return;
 
-  assert(PrintCrashIR && "Did not expect to get here without option set.");
+  assert((PrintOnCrash || !PrintOnCrashPath.empty()) &&
+         "Did not expect to get here without option set.");
   CrashReporter = nullptr;
 }
 
 void PrintCrashIRInstrumentation::registerCallbacks(
     PassInstrumentationCallbacks &PIC) {
-  if (!PrintCrashIR || CrashReporter)
+  if ((!PrintOnCrash && PrintOnCrashPath.empty()) || CrashReporter)
     return;
 
   sys::AddSignalHandler(SignalHandler, nullptr);
   CrashReporter = this;
 
-  PIC.registerBeforeNonSkippedPassCallback([&PIC, this](StringRef PassID,
-                                                        Any IR) {
+  PIC.registerBeforeNonSkippedPassCallback(
+      [&PIC, this](StringRef PassID, Any IR) {
         SavedIR.clear();
         raw_string_ostream OS(SavedIR);
         OS << formatv("*** Dump of {0}IR Before Last Pass {1}",
                       llvm::forcePrintModuleIR() ? "Module " : "", PassID);
         if (!isInteresting(IR, PassID, PIC.getPassNameForClassName(PassID))) {
           OS << " Filtered Out ***\n";
           return;
         }
         OS << " Started ***\n";
         unwrapAndPrint(OS, IR);
       });
 }
 
 void StandardInstrumentations::registerCallbacks(
     PassInstrumentationCallbacks &PIC, ModuleAnalysisManager *MAM) {
   PrintIR.registerCallbacks(PIC);
   PrintPass.registerCallbacks(PIC);
   TimePasses.registerCallbacks(PIC);
   OptNone.registerCallbacks(PIC);

llvm/test/Other/print-on-crash.ll

 ; A test that the hidden option -print-on-crash properly sets a signal handler
 ; which gets called when a pass crashes.  The trigger-crash pass asserts.
 
 ; RUN: not --crash opt -print-on-crash -passes=trigger-crash < %s 2>&1 | FileCheck %s --check-prefix=CHECK_SIMPLE
 
+; RUN: not --crash opt -print-on-crash-path=%t -passes=trigger-crash < %s
+; RUN: FileCheck %s --check-prefix=CHECK_SIMPLE --input-file=%t
+
 ; A test that the signal handler set by the  hidden option -print-on-crash
 ; is not called when no pass crashes.
 
-; RUN: opt -print-on-crash -passes="default<O2>" < %s 2>&1 | FileCheck %s --check-prefix=CHECK_NO_CRASH
+; RUN: opt -disable-output -print-on-crash -passes="default<O2>" < %s 2>&1 | FileCheck %s --check-prefix=CHECK_NO_CRASH --allow-empty
 
 ; RUN: not --crash opt -print-on-crash -print-module-scope -passes=trigger-crash < %s 2>&1 | FileCheck %s --check-prefix=CHECK_MODULE
 
 ; RUN: not --crash opt -print-on-crash -print-module-scope -passes=trigger-crash -filter-passes=trigger-crash < %s 2>&1 | FileCheck %s --check-prefix=CHECK_MODULE
 
 ; RUN: not --crash opt -print-on-crash -print-module-scope -passes=trigger-crash -filter-passes=blah < %s 2>&1 | FileCheck %s --check-prefix=CHECK_FILTERED
 
 ; CHECK_SIMPLE: *** Dump of IR Before Last Pass {{.*}} Started ***