Revert "Error out if the checksum mismatch is high"

This reverts commit f25b13f.

Author: wlei-llvm

llvm/lib/Transforms/IPO/SampleProfile.cpp

@@ -234,25 +234,6 @@ static cl::opt<unsigned> ProfileICPRelativeHotnessSkip(
     cl::desc(
         "Skip relative hotness check for ICP up to given number of targets."));
 
-static cl::opt<unsigned> ChecksumMismatchFuncHotBlockSkip(
-    "checksum-mismatch-func-hot-block-skip", cl::Hidden, cl::init(100),
-    cl::desc("For checksum-mismatch error check, skip checking the function "
-             "that the num of its hot(on average) blocks is smaller than the "
-             "given number."));
-
-static cl::opt<unsigned> ChecksumMismatchNumFuncSkip(
-    "checksum-mismatch-num-func-skip", cl::Hidden, cl::init(100),
-    cl::desc(
-        "For checksum-mismatch error check, skip the check if the number of "
-        "total selected function is smaller than the given number."));
-
-static cl::opt<unsigned> ChecksumMismatchErrorThreshold(
-    "checksum-mismatch-error-threshold", cl::Hidden, cl::init(90),
-    cl::desc(
-        "For checksum-mismatch error check, error out if the percentage of "
-        "function mismatched-checksum is higher than the given percentage "
-        "threshold"));
-
 static cl::opt<bool> CallsitePrioritizedInline(
     "sample-profile-prioritized-inline", cl::Hidden,
 
@@ -649,8 +630,6 @@ class SampleProfileLoader final : public SampleProfileLoaderBaseImpl<Function> {
   std::vector<Function *> buildFunctionOrder(Module &M, LazyCallGraph &CG);
   std::unique_ptr<ProfiledCallGraph> buildProfiledCallGraph(Module &M);
   void generateMDProfMetadata(Function &F);
-  bool errorIfHighChecksumMismatch(Module &M, ProfileSummaryInfo *PSI,
-                                   const SampleProfileMap &Profiles);
 
   /// Map from function name to Function *. Used to find the function from
   /// the function name. If the function name contains suffix, additional
@@ -1211,7 +1190,7 @@ void SampleProfileLoader::findExternalInlineCandidate(
         CalleeSample->getContext().hasAttribute(ContextShouldBeInlined);
     if (!PreInline && CalleeSample->getHeadSamplesEstimate() < Threshold)
       continue;
-
+    
     Function *Func = SymbolMap.lookup(CalleeSample->getFunction());
     // Add to the import list only when it's defined out of module.
     if (!Func || Func->isDeclaration())
@@ -2205,61 +2184,6 @@ bool SampleProfileLoader::doInitialization(Module &M,
   return true;
 }
 
-// Note that this is a module-level check. Even if one module is errored out,
-// the entire build will be errored out. However, the user could make big
-// changes to functions in single module but those changes might not be
-// performance significant to the whole binary. Therefore, we use a conservative
-// approach to make sure we only error out if it globally impacts the binary
-// performance. To achieve this, we use heuristics to select a reasonable
-// big set of functions that are supposed to be globally performance
-// significant, only compute and check the mismatch within those functions. The
-// function selection is based on two criteria: 1) The function is "hot" enough,
-// which is tuned by a hotness-based flag(ChecksumMismatchFuncHotBlockSkip). 2)
-// The num of function is large enough which is tuned by the
-// ChecksumMismatchNumFuncSkip flag.
-bool SampleProfileLoader::errorIfHighChecksumMismatch(
-    Module &M, ProfileSummaryInfo *PSI, const SampleProfileMap &Profiles) {
-  assert(FunctionSamples::ProfileIsProbeBased &&
-         "Only support for probe-based profile");
-  uint64_t TotalSelectedFunc = 0;
-  uint64_t NumMismatchedFunc = 0;
-  for (const auto &I : Profiles) {
-    const auto &FS = I.second;
-    const auto *FuncDesc = ProbeManager->getDesc(FS.getGUID());
-    if (!FuncDesc)
-      continue;
-
-    // We want to select a set of functions that are globally performance
-    // significant, in other words, if those functions profiles are
-    // checksum-mismatched and dropped, the whole binary will likely be
-    // impacted, so here we use a hotness-based threshold to control the
-    // selection.
-    if (FS.getTotalSamples() >=
-        ChecksumMismatchFuncHotBlockSkip * PSI->getOrCompHotCountThreshold())
-      continue;
-
-    TotalSelectedFunc++;
-    if (ProbeManager->profileIsHashMismatched(*FuncDesc, FS))
-      NumMismatchedFunc++;
-  }
-  // Make sure that the num of selected function is not too small to distinguish
-  // from the user's benign changes.
-  if (TotalSelectedFunc < ChecksumMismatchNumFuncSkip)
-    return false;
-
-  // Finally check the mismatch percentage against the threshold.
-  if (NumMismatchedFunc * 100 >=
-      TotalSelectedFunc * ChecksumMismatchErrorThreshold) {
-    auto &Ctx = M.getContext();
-    const char *Msg =
-        "The FDO profile is too old and will cause big performance regression, "
-        "please drop the profile and re-collect a new one.";
-    Ctx.diagnose(DiagnosticInfoSampleProfile(M.getModuleIdentifier(), Msg));
-    return true;
-  }
-  return false;
-}
-
 void SampleProfileMatcher::findIRAnchors(
     const Function &F, std::map<LineLocation, StringRef> &IRAnchors) {
   // For inlined code, recover the original callsite and callee by finding the
@@ -2791,12 +2715,6 @@ bool SampleProfileLoader::runOnModule(Module &M, ModuleAnalysisManager *AM,
                         ProfileSummary::PSK_Sample);
     PSI->refresh();
   }
-
-  // Error out if the profile checksum mismatch is too high.
-  if (FunctionSamples::ProfileIsProbeBased &&
-      errorIfHighChecksumMismatch(M, PSI, Reader->getProfiles()))
-    return false;
-
   // Compute the total number of samples collected in this profile.
   for (const auto &I : Reader->getProfiles())
     TotalCollectedSamples += I.second.getTotalSamples();