Bugpoint support for miscompilations that result in a crash.

This change allows bugpoint to pinpoint the "opt" pass and bitcode
segment responsible for a crash caused by miscompilation. At least it
works well for me now, without having to create any custom execution
wrappers.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131186 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 20 insertions, 5 deletions

diff --git a/tools/bugpoint/ExecutionDriver.cpp b/tools/bugpoint/ExecutionDriver.cpp
index 9be9dfd650..77c01ac552 100644
--- a/tools/bugpoint/ExecutionDriver.cpp
+++ b/tools/bugpoint/ExecutionDriver.cpp
@@ -475,7 +475,7 @@ bool BugDriver::createReferenceFile(Module *M, const std::string &Filename) {
 /// diffProgram - This method executes the specified module and diffs the
 /// output against the file specified by ReferenceOutputFile.  If the output
 /// is different, 1 is returned.  If there is a problem with the code
-/// generator (e.g., llc crashes), this will return -1 and set Error.
+/// generator (e.g., llc crashes), this will set ErrMsg.
 ///
 bool BugDriver::diffProgram(const Module *Program,
                             const std::string &BitcodeFile,
diff --git a/tools/bugpoint/Miscompilation.cpp b/tools/bugpoint/Miscompilation.cpp
index a9db38f20c..1834fe1e12 100644
--- a/tools/bugpoint/Miscompilation.cpp
+++ b/tools/bugpoint/Miscompilation.cpp
@@ -624,9 +624,10 @@ DebugAMiscompilation(BugDriver &BD,
   if (!BugpointIsInterrupted)
     ReduceMiscompilingFunctions(BD, TestFn).reduceList(MiscompiledFunctions,
                                                        Error);
-  if (!Error.empty())
+  if (!Error.empty()) {
+    errs() << "\n***Cannot reduce functions: ";
     return MiscompiledFunctions;
-
+  }
   outs() << "\n*** The following function"
          << (MiscompiledFunctions.size() == 1 ? " is" : "s are")
          << " being miscompiled: ";
diff --git a/tools/bugpoint/ToolRunner.cpp b/tools/bugpoint/ToolRunner.cpp
index 6c46ef18eb..9c3e6121f2 100644
--- a/tools/bugpoint/ToolRunner.cpp
+++ b/tools/bugpoint/ToolRunner.cpp
@@ -50,6 +50,11 @@ namespace {
           cl::desc("Remote execution (rsh/ssh) extra options"));
 }
 
+// Add a prefix to ErrMsg if the program is terminated by a signal to
+// distinguish compiled program crashes from other execution
+// failures. Miscompilation likely to results in SIGSEGV.
+static const char *SignalPrefix = "Signal - ";
+
 /// RunProgramWithTimeout - This function provides an alternate interface
 /// to the sys::Program::ExecuteAndWait interface.
 /// @see sys::Program::ExecuteAndWait
@@ -77,7 +82,7 @@ static int RunProgramWithTimeout(const sys::Path &ProgramPath,
 
   return
     sys::Program::ExecuteAndWait(ProgramPath, Args, 0, redirects,
-                                 NumSeconds, MemoryLimit, ErrMsg);
+                                 NumSeconds, MemoryLimit, ErrMsg, SignalPrefix);
 }
 
 /// RunProgramRemotelyWithTimeout - This function runs the given program
@@ -854,9 +859,18 @@ int GCC::ExecuteProgram(const std::string &ProgramFile,
 
   if (RemoteClientPath.isEmpty()) {
     DEBUG(errs() << "<run locally>");
-    return RunProgramWithTimeout(OutputBinary, &ProgramArgs[0],
+    int ExitCode = RunProgramWithTimeout(OutputBinary, &ProgramArgs[0],
         sys::Path(InputFile), sys::Path(OutputFile), sys::Path(OutputFile),
         Timeout, MemoryLimit, Error);
+    // Treat a signal (usually SIGSEGV) as part of the program output so that
+    // crash-causing miscompilation is handled seamlessly.
+    if (Error->find(SignalPrefix) == 0) {
+      std::ofstream outFile(OutputFile.c_str(), std::ios_base::app);
+      outFile << *Error << '\n';
+      outFile.close();
+      Error->clear();
+    }
+    return ExitCode;
   } else {
     outs() << "<run remotely>"; outs().flush();
     return RunProgramRemotelyWithTimeout(sys::Path(RemoteClientPath),