[llvm] [UBSAN] Emit optimization remarks (PR #88304)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-ir

Author: Vitaly Buka (vitalybuka)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/88304.diff


2 Files Affected:

- (modified) llvm/lib/IR/DiagnosticInfo.cpp (+5-1) 
- (modified) llvm/lib/Transforms/Instrumentation/LowerAllowCheckPass.cpp (+29-3) 


``````````diff
diff --git a/llvm/lib/IR/DiagnosticInfo.cpp b/llvm/lib/IR/DiagnosticInfo.cpp
index 342c4cbbc39d65..31971b179fb4be 100644
--- a/llvm/lib/IR/DiagnosticInfo.cpp
+++ b/llvm/lib/IR/DiagnosticInfo.cpp
@@ -179,8 +179,12 @@ DiagnosticInfoOptimizationBase::Argument::Argument(StringRef Key,
   else if (isa<Constant>(V)) {
     raw_string_ostream OS(Val);
     V->printAsOperand(OS, /*PrintType=*/false);
-  } else if (auto *I = dyn_cast<Instruction>(V))
+  } else if (auto *I = dyn_cast<Instruction>(V)) {
     Val = I->getOpcodeName();
+  } else if (auto *MD = dyn_cast<MetadataAsValue>(V)) {
+    if (auto *S = dyn_cast<MDString>(MD->getMetadata()))
+      Val = S->getString();
+  }
 }
 
 DiagnosticInfoOptimizationBase::Argument::Argument(StringRef Key, const Type *T)
diff --git a/llvm/lib/Transforms/Instrumentation/LowerAllowCheckPass.cpp b/llvm/lib/Transforms/Instrumentation/LowerAllowCheckPass.cpp
index cdc8318f088c27..6c5a20227d0a36 100644
--- a/llvm/lib/Transforms/Instrumentation/LowerAllowCheckPass.cpp
+++ b/llvm/lib/Transforms/Instrumentation/LowerAllowCheckPass.cpp
@@ -10,11 +10,16 @@
 
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Analysis/OptimizationRemarkEmitter.h"
 #include "llvm/Analysis/ProfileSummaryInfo.h"
 #include "llvm/IR/Constant.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/Metadata.h"
 #include "llvm/Support/RandomNumberGenerator.h"
 #include <memory>
 #include <random>
@@ -35,8 +40,26 @@ static cl::opt<float>
 STATISTIC(NumChecksTotal, "Number of checks");
 STATISTIC(NumChecksRemoved, "Number of removed checks");
 
+static void emitRemark(IntrinsicInst *II, OptimizationRemarkEmitter &ORE,
+                       bool Removed) {
+  ore::NV Kind("Kind", II->getArgOperand(0));
+  ore::NV BB("Block", II->getParent()->getName());
+  if (Removed) {
+    ORE.emit([&]() {
+      return OptimizationRemark(DEBUG_TYPE, "Removed", II)
+             << "Removed check: Kind=" << Kind << " BB=" << BB;
+    });
+  } else {
+    ORE.emit([&]() {
+      return OptimizationRemarkMissed(DEBUG_TYPE, "Allowed", II)
+             << "Allowed check: Kind=" << Kind << " BB=" << BB;
+    });
+  }
+}
+
 static bool removeUbsanTraps(Function &F, const BlockFrequencyInfo &BFI,
-                             const ProfileSummaryInfo *PSI) {
+                             const ProfileSummaryInfo *PSI,
+                             OptimizationRemarkEmitter &ORE) {
   SmallVector<std::pair<IntrinsicInst *, bool>, 16> ReplaceWithValue;
   std::unique_ptr<RandomNumberGenerator> Rng;
 
@@ -75,6 +98,7 @@ static bool removeUbsanTraps(Function &F, const BlockFrequencyInfo &BFI,
         });
         if (ToRemove)
           ++NumChecksRemoved;
+        emitRemark(II, ORE, ToRemove);
         break;
       }
       default:
@@ -99,9 +123,11 @@ PreservedAnalyses LowerAllowCheckPass::run(Function &F,
   ProfileSummaryInfo *PSI =
       MAMProxy.getCachedResult<ProfileSummaryAnalysis>(*F.getParent());
   BlockFrequencyInfo &BFI = AM.getResult<BlockFrequencyAnalysis>(F);
+  OptimizationRemarkEmitter &ORE =
+      AM.getResult<OptimizationRemarkEmitterAnalysis>(F);
 
-  return removeUbsanTraps(F, BFI, PSI) ? PreservedAnalyses::none()
-                                       : PreservedAnalyses::all();
+  return removeUbsanTraps(F, BFI, PSI, ORE) ? PreservedAnalyses::none()
+                                            : PreservedAnalyses::all();
 }
 
 bool LowerAllowCheckPass::IsRequested() {

``````````

</details>


https://github.com/llvm/llvm-project/pull/88304