[llc/opt] Add an option to run all passes twice
Summary: Lately, I have submitted a number of patches to fix bugs that
only occurred when using the same pass manager to compile multiple
modules (generally these bugs are failure to reset some persistent
state). Unfortunately I don't think there is currently a way to test
that from the command line. This adds a very simple flag to both llc
and opt, under which the tools will simply re-run their respective
pass pipelines using the same pass manager on (a clone of the same
module). Additionally, we verify that both outputs are bitwise the
same.
Reviewers: yaron.keren
Subscribers: loladiro, yaron.keren, kcc, llvm-commits
Differential Revision: http://reviews.llvm.org/D14965
llvm-svn: 254774
diff --git a/llvm/tools/opt/opt.cpp b/llvm/tools/opt/opt.cpp
index 5fe2f03..c1510a7 100644
--- a/llvm/tools/opt/opt.cpp
+++ b/llvm/tools/opt/opt.cpp
@@ -28,6 +28,7 @@
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/IRPrintingPasses.h"
#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/LegacyPassManager.h"
#include "llvm/IR/LegacyPassNameParser.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Verifier.h"
@@ -36,7 +37,6 @@
#include "llvm/LinkAllIR.h"
#include "llvm/LinkAllPasses.h"
#include "llvm/MC/SubtargetFeature.h"
-#include "llvm/IR/LegacyPassManager.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Host.h"
@@ -51,6 +51,7 @@
#include "llvm/Support/ToolOutputFile.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Transforms/IPO/PassManagerBuilder.h"
+#include "llvm/Transforms/Utils/Cloning.h"
#include <algorithm>
#include <memory>
using namespace llvm;
@@ -190,6 +191,11 @@
cl::desc("Preserve use-list order when writing LLVM assembly."),
cl::init(false), cl::Hidden);
+static cl::opt<bool>
+ RunTwice("run-twice",
+ cl::desc("Run all passes twice, re-using the same pass manager."),
+ cl::init(false), cl::Hidden);
+
static inline void addPass(legacy::PassManagerBase &PM, Pass *P) {
// Add the pass to the pass manager...
PM.add(P);
@@ -582,14 +588,25 @@
if (!NoVerify && !VerifyEach)
Passes.add(createVerifierPass());
+ // In run twice mode, we want to make sure the output is bit-by-bit
+ // equivalent if we run the pass manager again, so setup two buffers and
+ // a stream to write to them. Note that llc does something similar and it
+ // may be worth to abstract this out in the future.
+ SmallVector<char, 0> Buffer;
+ SmallVector<char, 0> CompileTwiceBuffer;
+ std::unique_ptr<raw_svector_ostream> BOS;
+ raw_ostream *OS = &Out->os();
+ if (RunTwice) {
+ BOS = make_unique<raw_svector_ostream>(Buffer);
+ OS = BOS.get();
+ }
+
// Write bitcode or assembly to the output as the last step...
if (!NoOutput && !AnalyzeOnly) {
if (OutputAssembly)
- Passes.add(
- createPrintModulePass(Out->os(), "", PreserveAssemblyUseListOrder));
+ Passes.add(createPrintModulePass(*OS, "", PreserveAssemblyUseListOrder));
else
- Passes.add(
- createBitcodeWriterPass(Out->os(), PreserveBitcodeUseListOrder));
+ Passes.add(createBitcodeWriterPass(*OS, PreserveBitcodeUseListOrder));
}
// Before executing passes, print the final values of the LLVM options.
@@ -598,6 +615,27 @@
// Now that we have all of the passes ready, run them.
Passes.run(*M);
+ // If requested, run all passes again with the same pass manager to catch
+ // bugs caused by persistent state in the passes
+ if (RunTwice) {
+ CompileTwiceBuffer = Buffer;
+ Buffer.clear();
+ std::unique_ptr<Module> M2(CloneModule(M.get()));
+ Passes.run(*M2);
+ if (Buffer.size() != CompileTwiceBuffer.size() ||
+ (memcmp(Buffer.data(), CompileTwiceBuffer.data(), Buffer.size()) !=
+ 0)) {
+ errs() << "Running the pass manager twice changed the output.\n"
+ "Writing the result of the second run to the specified output."
+ "To generate the one-run comparison binary, just run without\n"
+ "the compile-twice option\n";
+ Out->os() << BOS->str();
+ Out->keep();
+ return 1;
+ }
+ Out->os() << BOS->str();
+ }
+
// Declare success.
if (!NoOutput || PrintBreakpoints)
Out->keep();