[llvm] Modify BoundsSan to improve debuggability (PR #65972)

[Vitaly Buka via llvm-commits]

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@@ -180,19 +183,27 @@ static bool addBoundsChecking(Function &F, TargetLibraryInfo &TLI,
   // will create a fresh block every time it is called.
   BasicBlock *TrapBB = nullptr;
   auto GetTrapBB = [&TrapBB](BuilderTy &IRB) {
-    if (TrapBB && SingleTrapBB)
-      return TrapBB;
-
     Function *Fn = IRB.GetInsertBlock()->getParent();
-    // FIXME: This debug location doesn't make a lot of sense in the
-    // `SingleTrapBB` case.
     auto DebugLoc = IRB.getCurrentDebugLocation();
     IRBuilder<>::InsertPointGuard Guard(IRB);
+
+    if (TrapBB && SingleTrapBB && !DebugTrapBB)
+      return TrapBB;
+
     TrapBB = BasicBlock::Create(Fn->getContext(), "trap", Fn);
     IRB.SetInsertPoint(TrapBB);
 
-    auto *F = Intrinsic::getDeclaration(Fn->getParent(), Intrinsic::trap);
-    CallInst *TrapCall = IRB.CreateCall(F, {});
+    Intrinsic::ID IntrID = DebugTrapBB ? Intrinsic::ubsantrap : Intrinsic::trap;
+    auto *F = Intrinsic::getDeclaration(Fn->getParent(), IntrID);
+
+    CallInst *TrapCall;
+    if (DebugTrapBB) {
+      TrapCall =
+          IRB.CreateCall(F, ConstantInt::get(IRB.getInt8Ty(), Fn->size()));
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vitalybuka wrote:

>> (TrapBB->getParent()->size() * 0x10000 + CheckHandlerID)

> Why * 0x10000 ?

anything that above CheckHandlerID so lower two bytes are still CheckHandlerID
and upper bytes you counter 

but i missed that it's i8
So keep your version

https://github.com/llvm/llvm-project/pull/65972