Initial implementation of optimization bisect support.

This patch implements a optimization bisect feature, which will allow optimizations to be selectively disabled at compile time in order to track down test failures that are caused by incorrect optimizations.

The bisection is enabled using a new command line option (-opt-bisect-limit).  Individual passes that may be skipped call the OptBisect object (via an LLVMContext) to see if they should be skipped based on the bisect limit.  A finer level of control (disabling individual transformations) can be managed through an addition OptBisect method, but this is not yet used.

The skip checking in this implementation is based on (and replaces) the skipOptnoneFunction check.  Where that check was being called, a new call has been inserted in its place which checks the bisect limit and the optnone attribute.  A new function call has been added for module and SCC passes that behaves in a similar way.

Differential Revision: http://reviews.llvm.org/D19172

llvm-svn: 267022

1 files changed, 176 insertions, 0 deletions

diff --git a/llvm/lib/IR/OptBisect.cpp b/llvm/lib/IR/OptBisect.cpp
new file mode 100644
index 00000000000..d06f40fce35
--- /dev/null
+++ b/llvm/lib/IR/OptBisect.cpp
@@ -0,0 +1,176 @@
+//===------- llvm/IR/OptBisect/Bisect.cpp - LLVM Bisect support --------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file implements support for a bisecting optimizations based on a
+/// command line option.
+///
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/CallGraphSCCPass.h"
+#include "llvm/Analysis/LazyCallGraph.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/OptBisect.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+
+static cl::opt<int> OptBisectLimit("opt-bisect-limit", cl::Hidden,
+                                   cl::init(INT_MAX), cl::Optional,
+                                   cl::desc("Maximum optimization to perform"));
+
+OptBisect::OptBisect() {
+  BisectEnabled = OptBisectLimit != INT_MAX;
+}
+
+static void printPassMessage(const StringRef &Name, int PassNum,
+                             StringRef TargetDesc, bool Running) {
+  StringRef Status = Running ? "" : "NOT ";
+  errs() << "BISECT: " << Status << "running pass "
+         << "(" << PassNum << ") " << Name << " on " << TargetDesc << "\n";
+}
+
+static void printCaseMessage(int CaseNum, StringRef Msg, bool Running) {
+  if (Running)
+    errs() << "BISECT: running case (";
+  else
+    errs() << "BISECT: NOT running case (";
+  errs() << CaseNum << "): " << Msg << "\n";
+}
+
+static std::string getDescription(const Module &M) {
+  return "module (" + M.getName().str() + ")";
+}
+
+static std::string getDescription(const Function &F) {
+  return "function (" + F.getName().str() + ")";
+}
+
+static std::string getDescription(const BasicBlock &BB) {
+  return "basic block (" + BB.getName().str() + ") in function (" +
+         BB.getParent()->getName().str() + ")";
+}
+
+static std::string getDescription(const Loop &L) {
+  // FIXME: I'd like to be able to provide a better description here, but
+  //        calling L->getHeader() would introduce a new dependency on the
+  //        LLVMCore library.
+  return "loop";
+}
+
+static std::string getDescription(const CallGraphSCC &SCC) {
+  std::string Desc = "SCC (";
+  bool First = true;
+  for (CallGraphNode *CGN : SCC) {
+    if (First)
+      First = false;
+    else
+      Desc += ", ";
+    Function *F = CGN->getFunction();
+    if (F)
+      Desc += F->getName();
+    else
+      Desc += "<<null function>>";
+  }
+  Desc += ")";
+  return Desc;
+}
+
+static std::string getDescription(const LazyCallGraph::SCC &SCC) {
+  std::string Desc = "SCC (";
+  bool First = true;
+  for (LazyCallGraph::Node &CGN : SCC) {
+    if (First)
+      First = false;
+    else
+      Desc += ", ";
+    Function &F = CGN.getFunction();
+    Desc += F.getName();
+  }
+  Desc += ")";
+  return Desc;
+}
+
+// Force instantiations.
+template bool OptBisect::shouldRunPass(const Pass *, const Module &);
+template bool OptBisect::shouldRunPass(const Pass *, const Function &);
+template bool OptBisect::shouldRunPass(const Pass *, const BasicBlock &);
+template bool OptBisect::shouldRunPass(const Pass *, const Loop &);
+template bool OptBisect::shouldRunPass(const Pass *, const CallGraphSCC &);
+template bool OptBisect::shouldRunPass(const StringRef PassName,
+                                       const Module &);
+template bool OptBisect::shouldRunPass(const StringRef PassName,
+                                       const Function &);
+template bool OptBisect::shouldRunPass(const StringRef PassName,
+                                       const BasicBlock &);
+template bool OptBisect::shouldRunPass(const StringRef PassName, const Loop &);
+template bool OptBisect::shouldRunPass(const StringRef PassName,
+                                       const LazyCallGraph::SCC &);
+
+template <class UnitT>
+bool OptBisect::shouldRunPass(const Pass *P, const UnitT &U) {
+  if (!BisectEnabled)
+    return true;
+  return checkPass(P->getPassName(), getDescription(U));
+}
+
+// Interface function for the new pass manager.
+template <class UnitT>
+bool OptBisect::shouldRunPass(const StringRef PassName, const UnitT &U) {
+  if (!BisectEnabled)
+    return true;
+  return checkPass(PassName, getDescription(U));
+}
+
+bool OptBisect::checkPass(const StringRef PassName,
+                          const StringRef TargetDesc) {
+  assert(BisectEnabled);
+
+  int CurBisectNum = ++LastBisectNum;
+  bool ShouldRun = (OptBisectLimit == -1 || CurBisectNum <= OptBisectLimit);
+  printPassMessage(PassName, CurBisectNum, TargetDesc, ShouldRun);
+  return ShouldRun;
+}
+
+bool OptBisect::shouldRunCase(const Twine &Msg) {
+  if (!BisectEnabled)
+    return true;
+  int CurFuelNum = ++LastBisectNum;
+  bool ShouldRun = (OptBisectLimit == -1 || CurFuelNum <= OptBisectLimit);
+  printCaseMessage(CurFuelNum, Msg.str(), ShouldRun);
+  return ShouldRun;
+}
+
+bool llvm::skipPassForModule(const StringRef PassName, const Module &M) {
+  return !M.getContext().getOptBisect().shouldRunPass(PassName, M);
+}
+
+bool llvm::skipPassForFunction(const StringRef PassName, const Function &F) {
+  return !F.getContext().getOptBisect().shouldRunPass(PassName, F);
+}
+#if 0
+bool llvm::skipPassForBasicBlock(const StringRef PassName, const BasicBlock &BB) {
+  return !BB.getContext().getOptBisect().shouldRunPass(PassName, BB);
+}
+
+bool llvm::skipPassForLoop(const StringRef PassName, const Loop &L) {
+  const Function *F = L.getHeader()->getParent();
+  if (!F)
+    return false;
+  return !F->getContext().getOptBisect().shouldRunPass(PassName, L);
+}
+#endif
+bool llvm::skipPassForSCC(const StringRef PassName, const LazyCallGraph::SCC &SCC) {
+  LLVMContext &Context = SCC.begin()->getFunction().getContext();
+  return !Context.getOptBisect().shouldRunPass(PassName, SCC);
+}
+