Add new hidden option -print-on-crash that prints out IR that caused opt pipeline to crash

A new hidden option -print-on-crash that prints the IR as it was upon entering
the last pass when there is a crash.

The IR is saved in its print form before each pass is started and a
signal handler is registered.  If the compilation crashes, the signal
handler will print the saved IR to dbgs().  This option
can be modified using -print-module-scope to get the IR for the complete
module.  Note that this option only works with the new pass manager.

Reviewed By: yrouban

Differential Revision: https://reviews.llvm.org/D86657

llvm/include/llvm/Passes/StandardInstrumentations.h

@@ -480,6 +480,25 @@ protected:
   std::unique_ptr<raw_fd_ostream> HTML;
 };
 
+// Print IR on crash.
+class PrintCrashIRInstrumentation {
+public:
+  PrintCrashIRInstrumentation()
+      : SavedIR("*** Dump of IR Before Last Pass Unknown ***") {}
+  ~PrintCrashIRInstrumentation();
+  void registerCallbacks(PassInstrumentationCallbacks &PIC);
+  void reportCrashIR();
+
+protected:
+  std::string SavedIR;
+
+private:
+  // The crash reporter that will report on a crash.
+  static PrintCrashIRInstrumentation *CrashReporter;
+  // Crash handler registered when print-on-crash is specified.
+  static void SignalHandler(void *);
+};
+
 /// This class provides an interface to register all the standard pass
 /// instrumentations and manages their state (if any).
 class StandardInstrumentations {
@@ -493,6 +512,7 @@ class StandardInstrumentations {
   PseudoProbeVerifier PseudoProbeVerification;
   InLineChangePrinter PrintChangedDiff;
   DotCfgChangeReporter WebsiteChangeReporter;
+  PrintCrashIRInstrumentation PrintCrashIR;
   VerifyInstrumentation Verify;
 
   bool VerifyEach;

llvm/lib/Passes/PassBuilder.cpp

@@ -375,6 +375,17 @@ bool shouldPopulateClassToPassNames() {
          !printAfterPasses().empty();
 }
 
+// A pass for testing -print-on-crash.
+// DO NOT USE THIS EXCEPT FOR TESTING!
+class TriggerCrashPass : public PassInfoMixin<TriggerCrashPass> {
+public:
+  PreservedAnalyses run(Module &, ModuleAnalysisManager &) {
+    abort();
+    return PreservedAnalyses::all();
+  }
+  static StringRef name() { return "TriggerCrashPass"; }
+};
+
 } // namespace
 
 PassBuilder::PassBuilder(TargetMachine *TM, PipelineTuningOptions PTO,

llvm/lib/Passes/PassRegistry.def

@@ -114,6 +114,7 @@ MODULE_PASS("strip-debug-declare", StripDebugDeclarePass())
 MODULE_PASS("strip-nondebug", StripNonDebugSymbolsPass())
 MODULE_PASS("strip-nonlinetable-debuginfo", StripNonLineTableDebugInfoPass())
 MODULE_PASS("synthetic-counts-propagation", SyntheticCountsPropagation())
+MODULE_PASS("trigger-crash", TriggerCrashPass())
 MODULE_PASS("verify", VerifierPass())
 MODULE_PASS("view-callgraph", CallGraphViewerPass())
 MODULE_PASS("wholeprogramdevirt", WholeProgramDevirtPass())

llvm/lib/Passes/StandardInstrumentations.cpp

@@ -28,12 +28,14 @@
 #include "llvm/IR/PrintPasses.h"
 #include "llvm/IR/Verifier.h"
 #include "llvm/Support/CommandLine.h"
+#include "llvm/Support/CrashRecoveryContext.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/GraphWriter.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Program.h"
 #include "llvm/Support/Regex.h"
+#include "llvm/Support/Signals.h"
 #include "llvm/Support/raw_ostream.h"
 #include <unordered_map>
 #include <unordered_set>
@@ -165,6 +167,12 @@ static cl::opt<std::string> DotCfgDir(
     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::init(false), cl::Hidden);
+
 namespace {
 
 // Perform a system based diff between \p Before and \p After, using
@@ -2115,6 +2123,51 @@ StandardInstrumentations::StandardInstrumentations(
                             ChangePrinter::PrintChangedDotCfgVerbose),
       Verify(DebugLogging), VerifyEach(VerifyEach) {}
 
+PrintCrashIRInstrumentation *PrintCrashIRInstrumentation::CrashReporter =
+    nullptr;
+
+void PrintCrashIRInstrumentation::reportCrashIR() { 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.");
+  CrashReporter->reportCrashIR();
+}
+
+PrintCrashIRInstrumentation::~PrintCrashIRInstrumentation() {
+  if (!CrashReporter)
+    return;
+
+  assert(PrintCrashIR && "Did not expect to get here without option set.");
+  CrashReporter = nullptr;
+}
+
+void PrintCrashIRInstrumentation::registerCallbacks(
+    PassInstrumentationCallbacks &PIC) {
+  if (!PrintCrashIR || CrashReporter)
+    return;
+
+  sys::AddSignalHandler(SignalHandler, nullptr);
+  CrashReporter = this;
+
+  PIC.registerBeforeNonSkippedPassCallback([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)) {
+      OS << " Filtered Out ***\n";
+      return;
+    }
+    OS << " Started ***\n";
+    unwrapAndPrint(OS, IR);
+  });
+}
+
 void StandardInstrumentations::registerCallbacks(
     PassInstrumentationCallbacks &PIC, FunctionAnalysisManager *FAM) {
   PrintIR.registerCallbacks(PIC);
@@ -2130,6 +2183,7 @@ void StandardInstrumentations::registerCallbacks(
     Verify.registerCallbacks(PIC);
   PrintChangedDiff.registerCallbacks(PIC);
   WebsiteChangeReporter.registerCallbacks(PIC);
+  PrintCrashIR.registerCallbacks(PIC);
 }
 
 template class ChangeReporter<std::string>;

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

@@ -0,0 +1,30 @@
+; 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
+
+; 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: 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=TriggerCrashPass < %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 ***
+; CHECK_SIMPLE: @main
+; CHECK_SIMPLE: entry:
+; CHECK_NO_CRASH-NOT: *** Dump of IR
+; CHECK_MODULE: *** Dump of Module IR Before Last Pass {{.*}} Started ***
+; CHECK_MODULE: ; ModuleID = {{.*}}
+; CHECK_FILTERED: *** Dump of Module IR Before Last Pass {{.*}} Filtered Out ***
+
+define i32 @main() {
+entry:
+  %retval = alloca i32, align 4
+  store i32 0, i32* %retval, align 4
+  ret i32 0
+}