llvm-reduce: Disable crash reports, symbolization and core dumps

[arsenm]

Summary

These are going to waste a lot of time and produce clutter when we're
bulk introducing crashes. Add a flag to disable this behavior in case
this matters to a reproducer.

[arsenm]

Use consistent overwrite behavior

[arsenm]

Forgot to commit overwrite behavior test

[aeubanks]

thanks, I've always manually added LLVM_DISABLE_SYMBOLIZATION to the reproducer, this is nicer

llvm/test/tools/llvm-reduce/Inputs/test-crash-vars.py

8

a comment here that both env vars being "1" is interesting would be nice, it took a non-trivial amount of time to work out

llvm/tools/llvm-reduce/llvm-reduce.cpp

115–116

win premerge bot is failing, you need

#ifdef _WIN32
#include <windows.h>
#endif

[arsenm]

Windows include, add another preserve environment test

[arsenm]

95abdeba6152c3fa15e96b4bababe6311bc9c118

[fhahn]

In D140388#4009398, @arsenm wrote:

95abdeba6152c3fa15e96b4bababe6311bc9c118

It might be good to include the review URL in the commit message so its easy to find the review from the commit and have Phabricator auto-close the review :)

llvm/test/tools/llvm-reduce/Inputs/test-crash-vars.py

+import os
+import sys
+
+disable_crash_report = os.getenv("LLVM_DISABLE_CRASH_REPORT")
+disable_symbolization = os.getenv("LLVM_DISABLE_SYMBOLIZATION")
+
+# Test that this is an explicitly set true value. If we preserve the
+# debug environment a pre-set explicit 0 should work.
+sys.exit(disable_crash_report != "1" or disable_symbolization != "1")

llvm/test/tools/llvm-reduce/disable-crash-reports.test

+# RUN: llvm-reduce --delta-passes=global-variables --test %python --test-arg %p/Inputs/test-crash-vars.py %p/Inputs/test-output-format.ll 2>&1 | FileCheck -check-prefix=INTERESTING %s
+
+# RUN: LLVM_DISABLE_CRASH_REPORT=0 llvm-reduce --delta-passes=global-variables --test %python --test-arg %p/Inputs/test-crash-vars.py %p/Inputs/test-output-format.ll 2>&1 | FileCheck -check-prefix=INTERESTING %s
+
+# RUN: not llvm-reduce --preserve-debug-environment --delta-passes=global-variables --test %python --test-arg %p/Inputs/test-crash-vars.py %p/Inputs/test-output-format.ll 2>&1 | FileCheck -check-prefix=NOTINTERESTING %s
+
+# RUN: LLVM_DISABLE_CRASH_REPORT=0 not llvm-reduce --preserve-debug-environment --delta-passes=global-variables --test %python --test-arg %p/Inputs/test-crash-vars.py %p/Inputs/test-output-format.ll 2>&1 | FileCheck -check-prefix=NOTINTERESTING %s
+
+# RUN: LLVM_DISABLE_CRASH_REPORT=1 LLVM_DISABLE_SYMBOLIZATION=1 llvm-reduce --preserve-debug-environment --delta-passes=global-variables --test %python --test-arg %p/Inputs/test-crash-vars.py %p/Inputs/test-output-format.ll 2>&1 | FileCheck -check-prefix=INTERESTING %s
+
+INTERESTING: Done reducing! Reduced testcase:
+NOTINTERESTING: Input isn't interesting! Verify interesting-ness test

llvm/tools/llvm-reduce/llvm-reduce.cpp

 // into the bugpoint tool itself.
 //
 //===----------------------------------------------------------------------===//
 
 #include "DeltaManager.h"
 #include "ReducerWorkItem.h"
 #include "TestRunner.h"
 #include "llvm/CodeGen/CommandFlags.h"
-
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/InitLLVM.h"
+#include "llvm/Support/Process.h"
 #include "llvm/Support/WithColor.h"
 #include "llvm/Support/raw_ostream.h"
 #include <system_error>
 #include <vector>
 
+#ifdef _WIN32
+#include <windows.h>
+#endif
+
 using namespace llvm;
 
 cl::OptionCategory LLVMReduceOptions("llvm-reduce options");
 
 static cl::opt<bool> Help("h", cl::desc("Alias for -help"), cl::Hidden,
                           cl::cat(LLVMReduceOptions));
 static cl::opt<bool> Version("v", cl::desc("Alias for -version"), cl::Hidden,
                              cl::cat(LLVMReduceOptions));
 
+static cl::opt<bool> PreserveDebugEnvironment(
+    "preserve-debug-environment",
+    cl::desc("Don't disable features used for crash "
+             "debugging (crash reports, llvm-symbolizer and core dumps)"),
+    cl::cat(LLVMReduceOptions));
+
 static cl::opt<bool>
     PrintDeltaPasses("print-delta-passes",
                      cl::desc("Print list of delta passes, passable to "
                               "--delta-passes as a comma separated list"),
                      cl::cat(LLVMReduceOptions));
 
 static cl::opt<std::string> InputFilename(cl::Positional, cl::Required,
                                           cl::desc("<input llvm ll/bc file>"),
MaxPassIterations("max-pass-iterations",
                       cl::desc("Maximum number of times to run the full set "
                                "of delta passes (default=5)"),
                       cl::init(5), cl::cat(LLVMReduceOptions));
 
 static codegen::RegisterCodeGenFlags CGF;
 
 bool isReduced(ReducerWorkItem &M, const TestRunner &Test);
 
+/// Turn off crash debugging features
+///
+/// Crash is expected, so disable crash reports and symbolization to reduce
+/// output clutter and avoid potentially slow symbolization.
+static void disableEnvironmentDebugFeatures() {
+  sys::Process::PreventCoreFiles();
+
+  // TODO: Copied from not. Should have a wrapper around setenv.
+#ifdef _WIN32
+  SetEnvironmentVariableA("LLVM_DISABLE_CRASH_REPORT", "1");
+  SetEnvironmentVariableA("LLVM_DISABLE_SYMBOLIZATION", "1");
+#else
+  setenv("LLVM_DISABLE_CRASH_REPORT", "1", /*overwrite=*/1);
+  setenv("LLVM_DISABLE_SYMBOLIZATION", "1", /*overwrite=*/1);
+#endif
+}
+
 static std::pair<StringRef, bool> determineOutputType(bool IsMIR,
                                                       bool InputIsBitcode) {
   bool OutputBitcode = ForceOutputBitcode || InputIsBitcode;
 
   if (ReplaceInput) { // In-place
     OutputFilename = InputFilename.c_str();
   } else if (OutputFilename.empty()) {
     // Default to producing bitcode if the input was bitcode, if not explicitly
if (InputLanguage != InputLanguages::None) {
     ReduceModeMIR = true;
   }
 
   if (PrintDeltaPasses) {
     printDeltaPasses(errs());
     return 0;
   }
 
+  if (!PreserveDebugEnvironment)
+    disableEnvironmentDebugFeatures();
+
   LLVMContext Context;
   std::unique_ptr<TargetMachine> TM;
 
   auto [OriginalProgram, InputIsBitcode] =
       parseReducerWorkItem(Argv[0], InputFilename, Context, TM, ReduceModeMIR);
   if (!OriginalProgram) {
     return 1;
   }