llvm-project/llvm/tools/bugpoint/Miscompilation.cpp

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//===- Miscompilation.cpp - Debug program miscompilations -----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements program miscompilation debugging support.
//
//===----------------------------------------------------------------------===//
#include "BugDriver.h"
#include "ListReducer.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Linker.h"
#include "Support/FileUtilities.h"
using namespace llvm;
namespace {
class ReduceMiscompilingPasses : public ListReducer<const PassInfo*> {
BugDriver &BD;
public:
ReduceMiscompilingPasses(BugDriver &bd) : BD(bd) {}
virtual TestResult doTest(std::vector<const PassInfo*> &Prefix,
std::vector<const PassInfo*> &Suffix);
};
}
ReduceMiscompilingPasses::TestResult
ReduceMiscompilingPasses::doTest(std::vector<const PassInfo*> &Prefix,
std::vector<const PassInfo*> &Suffix) {
// First, run the program with just the Suffix passes. If it is still broken
// with JUST the kept passes, discard the prefix passes.
std::cout << "Checking to see if '" << getPassesString(Suffix)
<< "' compile correctly: ";
std::string BytecodeResult;
if (BD.runPasses(Suffix, BytecodeResult, false/*delete*/, true/*quiet*/)) {
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std::cerr << " Error running this sequence of passes"
<< " on the input program!\n";
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BD.setPassesToRun(Suffix);
BD.EmitProgressBytecode("pass-error", false);
exit(BD.debugOptimizerCrash());
}
// Check to see if the finished program matches the reference output...
if (BD.diffProgram(BytecodeResult, "", true /*delete bytecode*/)) {
std::cout << "nope.\n";
return KeepSuffix; // Miscompilation detected!
}
std::cout << "yup.\n"; // No miscompilation!
if (Prefix.empty()) return NoFailure;
// Next, see if the program is broken if we run the "prefix" passes first,
// then separately run the "kept" passes.
std::cout << "Checking to see if '" << getPassesString(Prefix)
<< "' compile correctly: ";
// If it is not broken with the kept passes, it's possible that the prefix
// passes must be run before the kept passes to break it. If the program
// WORKS after the prefix passes, but then fails if running the prefix AND
// kept passes, we can update our bytecode file to include the result of the
// prefix passes, then discard the prefix passes.
//
if (BD.runPasses(Prefix, BytecodeResult, false/*delete*/, true/*quiet*/)) {
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std::cerr << " Error running this sequence of passes"
<< " on the input program!\n";
BD.setPassesToRun(Prefix);
BD.EmitProgressBytecode("pass-error", false);
exit(BD.debugOptimizerCrash());
}
// If the prefix maintains the predicate by itself, only keep the prefix!
if (BD.diffProgram(BytecodeResult)) {
std::cout << "nope.\n";
removeFile(BytecodeResult);
return KeepPrefix;
}
std::cout << "yup.\n"; // No miscompilation!
// Ok, so now we know that the prefix passes work, try running the suffix
// passes on the result of the prefix passes.
//
Module *PrefixOutput = ParseInputFile(BytecodeResult);
if (PrefixOutput == 0) {
std::cerr << BD.getToolName() << ": Error reading bytecode file '"
<< BytecodeResult << "'!\n";
exit(1);
}
removeFile(BytecodeResult); // No longer need the file on disk
std::cout << "Checking to see if '" << getPassesString(Suffix)
<< "' passes compile correctly after the '"
<< getPassesString(Prefix) << "' passes: ";
Module *OriginalInput = BD.swapProgramIn(PrefixOutput);
if (BD.runPasses(Suffix, BytecodeResult, false/*delete*/, true/*quiet*/)) {
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std::cerr << " Error running this sequence of passes"
<< " on the input program!\n";
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BD.setPassesToRun(Suffix);
BD.EmitProgressBytecode("pass-error", false);
exit(BD.debugOptimizerCrash());
}
// Run the result...
if (BD.diffProgram(BytecodeResult, "", true/*delete bytecode*/)) {
std::cout << "nope.\n";
delete OriginalInput; // We pruned down the original input...
return KeepSuffix;
}
// Otherwise, we must not be running the bad pass anymore.
std::cout << "yup.\n"; // No miscompilation!
delete BD.swapProgramIn(OriginalInput); // Restore orig program & free test
return NoFailure;
}
namespace {
class ReduceMiscompilingFunctions : public ListReducer<Function*> {
BugDriver &BD;
public:
ReduceMiscompilingFunctions(BugDriver &bd) : BD(bd) {}
virtual TestResult doTest(std::vector<Function*> &Prefix,
std::vector<Function*> &Suffix) {
if (!Suffix.empty() && TestFuncs(Suffix))
return KeepSuffix;
if (!Prefix.empty() && TestFuncs(Prefix))
return KeepPrefix;
return NoFailure;
}
bool TestFuncs(const std::vector<Function*> &Prefix);
};
}
/// TestMergedProgram - Given two modules, link them together and run the
/// program, checking to see if the program matches the diff. If the diff
/// matches, return false, otherwise return true. If the DeleteInputs argument
/// is set to true then this function deletes both input modules before it
/// returns.
static bool TestMergedProgram(BugDriver &BD, Module *M1, Module *M2,
bool DeleteInputs) {
// Link the two portions of the program back to together.
std::string ErrorMsg;
if (!DeleteInputs) M1 = CloneModule(M1);
if (LinkModules(M1, M2, &ErrorMsg)) {
std::cerr << BD.getToolName() << ": Error linking modules together:"
<< ErrorMsg << "\n";
exit(1);
}
if (DeleteInputs) delete M2; // We are done with this module...
Module *OldProgram = BD.swapProgramIn(M1);
// Execute the program. If it does not match the expected output, we must
// return true.
bool Broken = BD.diffProgram();
// Delete the linked module & restore the original
BD.swapProgramIn(OldProgram);
if (DeleteInputs) delete M1;
return Broken;
}
bool ReduceMiscompilingFunctions::TestFuncs(const std::vector<Function*>&Funcs){
// Test to see if the function is misoptimized if we ONLY run it on the
// functions listed in Funcs.
std::cout << "Checking to see if the program is misoptimized when "
<< (Funcs.size()==1 ? "this function is" : "these functions are")
<< " run through the pass"
<< (BD.getPassesToRun().size() == 1 ? "" : "es") << ":";
PrintFunctionList(Funcs);
std::cout << "\n";
// Split the module into the two halves of the program we want.
Module *ToNotOptimize = CloneModule(BD.getProgram());
Module *ToOptimize = SplitFunctionsOutOfModule(ToNotOptimize, Funcs);
// Run the optimization passes on ToOptimize, producing a transformed version
// of the functions being tested.
std::cout << " Optimizing functions being tested: ";
Module *Optimized = BD.runPassesOn(ToOptimize, BD.getPassesToRun(),
/*AutoDebugCrashes*/true);
std::cout << "done.\n";
delete ToOptimize;
std::cout << " Checking to see if the merged program executes correctly: ";
bool Broken = TestMergedProgram(BD, Optimized, ToNotOptimize, true);
std::cout << (Broken ? " nope.\n" : " yup.\n");
return Broken;
}
/// ExtractLoops - Given a reduced list of functions that still exposed the bug,
/// check to see if we can extract the loops in the region without obscuring the
/// bug. If so, it reduces the amount of code identified.
static bool ExtractLoops(BugDriver &BD,
std::vector<Function*> &MiscompiledFunctions) {
bool MadeChange = false;
while (1) {
Module *ToNotOptimize = CloneModule(BD.getProgram());
Module *ToOptimize = SplitFunctionsOutOfModule(ToNotOptimize,
MiscompiledFunctions);
Module *ToOptimizeLoopExtracted = BD.ExtractLoop(ToOptimize);
if (!ToOptimizeLoopExtracted) {
// If the loop extractor crashed or if there were no extractible loops,
// then this chapter of our odyssey is over with.
delete ToNotOptimize;
delete ToOptimize;
return MadeChange;
}
std::cerr << "Extracted a loop from the breaking portion of the program.\n";
delete ToOptimize;
// Bugpoint is intentionally not very trusting of LLVM transformations. In
// particular, we're not going to assume that the loop extractor works, so
// we're going to test the newly loop extracted program to make sure nothing
// has broken. If something broke, then we'll inform the user and stop
// extraction.
if (TestMergedProgram(BD, ToOptimizeLoopExtracted, ToNotOptimize, false)) {
// Merged program doesn't work anymore!
std::cerr << " *** ERROR: Loop extraction broke the program. :("
<< " Please report a bug!\n";
std::cerr << " Continuing on with un-loop-extracted version.\n";
delete ToNotOptimize;
delete ToOptimizeLoopExtracted;
return MadeChange;
}
// Okay, the loop extractor didn't break the program. Run the series of
// optimizations on the loop extracted portion and see if THEY still break
// the program. If so, it was safe to extract these loops!
std::cout << " Running optimizations on loop extracted portion: ";
Module *Optimized = BD.runPassesOn(ToOptimizeLoopExtracted,
BD.getPassesToRun(),
/*AutoDebugCrashes*/true);
std::cout << "done.\n";
std::cout << " Checking to see if the merged program executes correctly: ";
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bool Broken = TestMergedProgram(BD, Optimized, ToNotOptimize, false);
delete Optimized;
if (!Broken) {
std::cout << "yup: loop extraction masked the problem. Undoing.\n";
// If the program is not still broken, then loop extraction did something
// that masked the error. Stop loop extraction now.
delete ToNotOptimize;
delete ToOptimizeLoopExtracted;
return MadeChange;
}
std::cout << "nope: loop extraction successful!\n";
// Okay, great! Now we know that we extracted a loop and that loop
// extraction both didn't break the program, and didn't mask the problem.
// Replace the current program with the loop extracted version, and try to
// extract another loop.
std::string ErrorMsg;
if (LinkModules(ToNotOptimize, ToOptimizeLoopExtracted, &ErrorMsg)) {
std::cerr << BD.getToolName() << ": Error linking modules together:"
<< ErrorMsg << "\n";
exit(1);
}
delete ToOptimizeLoopExtracted;
// All of the Function*'s in the MiscompiledFunctions list are in the old
// module. Make sure to update them to point to the corresponding functions
// in the new module.
for (unsigned i = 0, e = MiscompiledFunctions.size(); i != e; ++i) {
Function *OldF = MiscompiledFunctions[i];
Function *NewF =
ToNotOptimize->getFunction(OldF->getName(), OldF->getFunctionType());
MiscompiledFunctions[i] = NewF;
}
BD.setNewProgram(ToNotOptimize);
MadeChange = true;
}
}
/// debugMiscompilation - This method is used when the passes selected are not
/// crashing, but the generated output is semantically different from the
/// input.
///
bool BugDriver::debugMiscompilation() {
// Make sure something was miscompiled...
if (!ReduceMiscompilingPasses(*this).reduceList(PassesToRun)) {
std::cerr << "*** Optimized program matches reference output! No problem "
<< "detected...\nbugpoint can't help you with your problem!\n";
return false;
}
std::cout << "\n*** Found miscompiling pass"
<< (getPassesToRun().size() == 1 ? "" : "es") << ": "
<< getPassesString(getPassesToRun()) << "\n";
EmitProgressBytecode("passinput");
// Okay, now that we have reduced the list of passes which are causing the
// failure, see if we can pin down which functions are being
// miscompiled... first build a list of all of the non-external functions in
// the program.
std::vector<Function*> MiscompiledFunctions;
for (Module::iterator I = Program->begin(), E = Program->end(); I != E; ++I)
if (!I->isExternal())
MiscompiledFunctions.push_back(I);
// Do the reduction...
ReduceMiscompilingFunctions(*this).reduceList(MiscompiledFunctions);
std::cout << "\n*** The following function"
<< (MiscompiledFunctions.size() == 1 ? " is" : "s are")
<< " being miscompiled: ";
PrintFunctionList(MiscompiledFunctions);
std::cout << "\n";
// See if we can rip any loops out of the miscompiled functions and still
// trigger the problem.
if (ExtractLoops(*this, MiscompiledFunctions)) {
// Okay, we extracted some loops and the problem still appears. See if we
// can eliminate some of the created functions from being candidates.
// Do the reduction...
ReduceMiscompilingFunctions(*this).reduceList(MiscompiledFunctions);
std::cout << "\n*** The following function"
<< (MiscompiledFunctions.size() == 1 ? " is" : "s are")
<< " being miscompiled: ";
PrintFunctionList(MiscompiledFunctions);
std::cout << "\n";
}
// Output a bunch of bytecode files for the user...
std::cout << "Outputting reduced bytecode files which expose the problem:\n";
Module *ToNotOptimize = CloneModule(getProgram());
Module *ToOptimize = SplitFunctionsOutOfModule(ToNotOptimize,
MiscompiledFunctions);
std::cout << " Non-optimized portion: ";
std::swap(Program, ToNotOptimize);
EmitProgressBytecode("tonotoptimize", true);
setNewProgram(ToNotOptimize); // Delete hacked module.
std::cout << " Portion that is input to optimizer: ";
std::swap(Program, ToOptimize);
EmitProgressBytecode("tooptimize");
setNewProgram(ToOptimize); // Delete hacked module.
return false;
}