Revert "clang-misexpect: Profile Guided Validation of Performance Annotations in LLVM"

This reverts commit r371484: this broke sanitizer-x86_64-linux-fast bot.

llvm-svn: 371488

5 files changed, 8 insertions, 208 deletions

diff --git a/llvm/lib/Transforms/IPO/SampleProfile.cpp b/llvm/lib/Transforms/IPO/SampleProfile.cpp
index d0cf63b35f4..eb4ddfd179b 100644
--- a/llvm/lib/Transforms/IPO/SampleProfile.cpp
+++ b/llvm/lib/Transforms/IPO/SampleProfile.cpp
@@ -72,7 +72,6 @@
 #include "llvm/Transforms/Instrumentation.h"
 #include "llvm/Transforms/Utils/CallPromotionUtils.h"
 #include "llvm/Transforms/Utils/Cloning.h"
-#include "llvm/Transforms/Utils/MisExpect.h"
 #include <algorithm>
 #include <cassert>
 #include <cstdint>
@@ -1447,8 +1446,6 @@ void SampleProfileLoader::propagateWeights(Function &F) {
       }
     }
 
-    misexpect::verifyMisExpect(TI, Weights, TI->getContext());
-
     uint64_t TempWeight;
     // Only set weights if there is at least one non-zero weight.
     // In any other case, let the analyzer set weights.
diff --git a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
index c8cf1805c66..73a91d909a9 100644
--- a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
+++ b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
@@ -108,7 +108,6 @@
 #include "llvm/Transforms/Instrumentation.h"
 #include "llvm/Transforms/Instrumentation/PGOInstrumentation.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
-#include "llvm/Transforms/Utils/MisExpect.h"
 #include <algorithm>
 #include <cassert>
 #include <cstdint>
@@ -1777,9 +1776,6 @@ void llvm::setProfMetadata(Module *M, Instruction *TI,
                                            : Weights) {
     dbgs() << W << " ";
   } dbgs() << "\n";);
-
-  misexpect::verifyMisExpect(TI, Weights, TI->getContext());
-
   TI->setMetadata(LLVMContext::MD_prof, MDB.createBranchWeights(Weights));
   if (EmitBranchProbability) {
     std::string BrCondStr = getBranchCondString(TI);
diff --git a/llvm/lib/Transforms/Scalar/LowerExpectIntrinsic.cpp b/llvm/lib/Transforms/Scalar/LowerExpectIntrinsic.cpp
index cdb1d790667..0d67c0d740e 100644
--- a/llvm/lib/Transforms/Scalar/LowerExpectIntrinsic.cpp
+++ b/llvm/lib/Transforms/Scalar/LowerExpectIntrinsic.cpp
@@ -26,7 +26,6 @@
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Transforms/Scalar.h"
-#include "llvm/Transforms/Utils/MisExpect.h"
 
 using namespace llvm;
 
@@ -72,20 +71,15 @@ static bool handleSwitchExpect(SwitchInst &SI) {
   unsigned n = SI.getNumCases(); // +1 for default case.
   SmallVector<uint32_t, 16> Weights(n + 1, UnlikelyBranchWeight);
 
-  uint64_t Index = (Case == *SI.case_default()) ? 0 : Case.getCaseIndex() + 1;
-  Weights[Index] = LikelyBranchWeight;
-
-  SI.setMetadata(
-      LLVMContext::MD_misexpect,
-      MDBuilder(CI->getContext())
-          .createMisExpect(Index, LikelyBranchWeight, UnlikelyBranchWeight));
-
-  SI.setCondition(ArgValue);
-  misexpect::checkFrontendInstrumentation(SI);
+  if (Case == *SI.case_default())
+    Weights[0] = LikelyBranchWeight;
+  else
+    Weights[Case.getCaseIndex() + 1] = LikelyBranchWeight;
 
   SI.setMetadata(LLVMContext::MD_prof,
                  MDBuilder(CI->getContext()).createBranchWeights(Weights));
 
+  SI.setCondition(ArgValue);
   return true;
 }
 
@@ -286,28 +280,19 @@ template <class BrSelInst> static bool handleBrSelExpect(BrSelInst &BSI) {
 
   MDBuilder MDB(CI->getContext());
   MDNode *Node;
-  MDNode *ExpNode;
 
   if ((ExpectedValue->getZExtValue() == ValueComparedTo) ==
-      (Predicate == CmpInst::ICMP_EQ)) {
+      (Predicate == CmpInst::ICMP_EQ))
     Node = MDB.createBranchWeights(LikelyBranchWeight, UnlikelyBranchWeight);
-    ExpNode = MDB.createMisExpect(0, LikelyBranchWeight, UnlikelyBranchWeight);
-  } else {
+  else
     Node = MDB.createBranchWeights(UnlikelyBranchWeight, LikelyBranchWeight);
-    ExpNode = MDB.createMisExpect(1, LikelyBranchWeight, UnlikelyBranchWeight);
-  }
 
-  BSI.setMetadata(LLVMContext::MD_misexpect, ExpNode);
+  BSI.setMetadata(LLVMContext::MD_prof, Node);
 
   if (CmpI)
     CmpI->setOperand(0, ArgValue);
   else
     BSI.setCondition(ArgValue);
-
-  misexpect::checkFrontendInstrumentation(BSI);
-
-  BSI.setMetadata(LLVMContext::MD_prof, Node);
-
   return true;
 }
 
diff --git a/llvm/lib/Transforms/Utils/CMakeLists.txt b/llvm/lib/Transforms/Utils/CMakeLists.txt
index 115f543a8ec..c232aa6223c 100644
--- a/llvm/lib/Transforms/Utils/CMakeLists.txt
+++ b/llvm/lib/Transforms/Utils/CMakeLists.txt
@@ -40,7 +40,6 @@ add_llvm_library(LLVMTransformUtils
   LowerSwitch.cpp
   Mem2Reg.cpp
   MetaRenamer.cpp
-  MisExpect.cpp
   ModuleUtils.cpp
   NameAnonGlobals.cpp
   PredicateInfo.cpp
diff --git a/llvm/lib/Transforms/Utils/MisExpect.cpp b/llvm/lib/Transforms/Utils/MisExpect.cpp
deleted file mode 100644
index 26d3402bd27..00000000000
--- a/llvm/lib/Transforms/Utils/MisExpect.cpp
+++ /dev/null
@@ -1,177 +0,0 @@
-//===--- MisExpect.cpp - Check the use of llvm.expect with PGO data -------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-//
-// This contains code to emit warnings for potentially incorrect usage of the
-// llvm.expect intrinsic. This utility extracts the threshold values from
-// metadata associated with the instrumented Branch or Switch instruction. The
-// threshold values are then used to determine if a warning should be emmited.
-//
-// MisExpect metadata is generated when llvm.expect intrinsics are lowered see
-// LowerExpectIntrinsic.cpp
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Transforms/Utils/MisExpect.h"
-#include "llvm/ADT/Twine.h"
-#include "llvm/Analysis/OptimizationRemarkEmitter.h"
-#include "llvm/IR/Constants.h"
-#include "llvm/IR/DiagnosticInfo.h"
-#include "llvm/IR/Instruction.h"
-#include "llvm/IR/Instructions.h"
-#include "llvm/IR/LLVMContext.h"
-#include "llvm/Support/BranchProbability.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/FormatVariadic.h"
-#include <cstdint>
-#include <functional>
-#include <numeric>
-
-#define DEBUG_TYPE "misexpect"
-
-using namespace llvm;
-using namespace misexpect;
-
-namespace llvm {
-
-// Command line option to enable/disable the warning when profile data suggests
-// a mismatch with the use of the llvm.expect intrinsic
-static cl::opt<bool> PGOWarnMisExpect(
-    "pgo-warn-misexpect", cl::init(false), cl::Hidden,
-    cl::desc("Use this option to turn on/off "
-             "warnings about incorrect usage of llvm.expect intrinsics."));
-
-} // namespace llvm
-
-namespace {
-
-Instruction *getOprndOrInst(Instruction *I) {
-  assert(I != nullptr && "MisExpect target Instruction cannot be nullptr");
-  Instruction *Ret = nullptr;
-  if (auto *B = dyn_cast<BranchInst>(I)) {
-    Ret = dyn_cast<Instruction>(B->getCondition());
-  }
-  // TODO: Find a way to resolve condition location for switches
-  // Using the condition of the switch seems to often resolve to an earlier
-  // point in the program, i.e. the calculation of the switch condition, rather
-  // than the switches location in the source code. Thus, we should use the
-  // instruction to get source code locations rather than the condition to
-  // improve diagnostic output, such as the caret. If the same problem exists
-  // for branch instructions, then we should remove this function and directly
-  // use the instruction
-  //
-  // else if (auto S = dyn_cast<SwitchInst>(I)) {
-  // Ret = I;
-  //}
-  return Ret ? Ret : I;
-}
-
-void emitMisexpectDiagnostic(Instruction *I, LLVMContext &Ctx,
-                             uint64_t ProfCount, uint64_t TotalCount) {
-  double PercentageCorrect = (double)ProfCount / TotalCount;
-  auto PerString =
-      formatv("{0:P} ({1} / {2})", PercentageCorrect, ProfCount, TotalCount);
-  auto RemStr = formatv(
-      "Potential performance regression from use of the llvm.expect intrinsic: "
-      "Annotation was correct on {0} of profiled executions.",
-      PerString);
-  Twine Msg(PerString);
-  Instruction *Cond = getOprndOrInst(I);
-  if (PGOWarnMisExpect)
-    Ctx.diagnose(DiagnosticInfoMisExpect(Cond, Msg));
-  OptimizationRemarkEmitter ORE(I->getParent()->getParent());
-  ORE.emit(OptimizationRemark(DEBUG_TYPE, "misexpect", Cond) << RemStr.str());
-}
-
-} // namespace
-
-namespace llvm {
-namespace misexpect {
-
-void verifyMisExpect(Instruction *I, const SmallVector<uint32_t, 4> &Weights,
-                     LLVMContext &Ctx) {
-  if (auto *MisExpectData = I->getMetadata(LLVMContext::MD_misexpect)) {
-    auto *MisExpectDataName = dyn_cast<MDString>(MisExpectData->getOperand(0));
-    if (MisExpectDataName &&
-        MisExpectDataName->getString().equals("misexpect")) {
-      LLVM_DEBUG(llvm::dbgs() << "------------------\n");
-      LLVM_DEBUG(llvm::dbgs()
-                 << "Function: " << I->getFunction()->getName() << "\n");
-      LLVM_DEBUG(llvm::dbgs() << "Instruction: " << *I << ":\n");
-      LLVM_DEBUG(for (int Idx = 0, Size = Weights.size(); Idx < Size; ++Idx) {
-        llvm::dbgs() << "Weights[" << Idx << "] = " << Weights[Idx] << "\n";
-      });
-
-      // extract values from misexpect metadata
-      const auto *IndexCint =
-          mdconst::dyn_extract<ConstantInt>(MisExpectData->getOperand(1));
-      const auto *LikelyCInt =
-          mdconst::dyn_extract<ConstantInt>(MisExpectData->getOperand(2));
-      const auto *UnlikelyCInt =
-          mdconst::dyn_extract<ConstantInt>(MisExpectData->getOperand(3));
-
-      if (!IndexCint || !LikelyCInt || !UnlikelyCInt)
-        return;
-
-      const uint64_t Index = IndexCint->getZExtValue();
-      const uint64_t LikelyBranchWeight = LikelyCInt->getZExtValue();
-      const uint64_t UnlikelyBranchWeight = UnlikelyCInt->getZExtValue();
-      const uint64_t ProfileCount = Weights[Index];
-      const uint64_t CaseTotal = std::accumulate(
-          Weights.begin(), Weights.end(), (uint64_t)0, std::plus<uint64_t>());
-      const uint64_t NumUnlikelyTargets = Weights.size() - 1;
-
-      const uint64_t TotalBranchWeight =
-          LikelyBranchWeight + (UnlikelyBranchWeight * NumUnlikelyTargets);
-
-      const llvm::BranchProbability LikelyThreshold(LikelyBranchWeight,
-                                                    TotalBranchWeight);
-      uint64_t ScaledThreshold = LikelyThreshold.scale(CaseTotal);
-
-      LLVM_DEBUG(llvm::dbgs()
-                 << "Unlikely Targets: " << NumUnlikelyTargets << ":\n");
-      LLVM_DEBUG(llvm::dbgs() << "Profile Count: " << ProfileCount << ":\n");
-      LLVM_DEBUG(llvm::dbgs()
-                 << "Scaled Threshold: " << ScaledThreshold << ":\n");
-      LLVM_DEBUG(llvm::dbgs() << "------------------\n");
-      if (ProfileCount < ScaledThreshold)
-        emitMisexpectDiagnostic(I, Ctx, ProfileCount, CaseTotal);
-    }
-  }
-}
-
-void checkFrontendInstrumentation(Instruction &I) {
-  if (auto *MD = I.getMetadata(LLVMContext::MD_prof)) {
-    unsigned NOps = MD->getNumOperands();
-
-    // Only emit misexpect diagnostics if at least 2 branch weights are present.
-    // Less than 2 branch weights means that the profiling metadata is:
-    //    1) incorrect/corrupted
-    //    2) not branch weight metadata
-    //    3) completely deterministic
-    // In these cases we should not emit any diagnostic related to misexpect.
-    if (NOps < 3)
-      return;
-
-    // Operand 0 is a string tag "branch_weights"
-    if (MDString *Tag = cast<MDString>(MD->getOperand(0))) {
-      if (Tag->getString().equals("branch_weights")) {
-        SmallVector<uint32_t, 4> RealWeights(NOps - 1);
-        for (unsigned i = 1; i < NOps; i++) {
-          ConstantInt *Value =
-              mdconst::dyn_extract<ConstantInt>(MD->getOperand(i));
-          RealWeights[i - 1] = Value->getZExtValue();
-        }
-        verifyMisExpect(&I, RealWeights, I.getContext());
-      }
-    }
-  }
-}
-
-} // namespace misexpect
-} // namespace llvm
-#undef DEBUG_TYPE