[clang] [llvm] [sancov] Introduce optional callback for stack-depth tracking (PR #138323)

[Marco Elver via llvm-commits]

================
@@ -1078,22 +1091,65 @@ void ModuleSanitizerCoverage::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
     Store->setNoSanitizeMetadata();
   }
   if (Options.StackDepth && IsEntryBB && !IsLeafFunc) {
-    // Check stack depth.  If it's the deepest so far, record it.
     Module *M = F.getParent();
-    auto FrameAddrPtr = IRB.CreateIntrinsic(
-        Intrinsic::frameaddress,
-        IRB.getPtrTy(M->getDataLayout().getAllocaAddrSpace()),
-        {Constant::getNullValue(Int32Ty)});
-    auto FrameAddrInt = IRB.CreatePtrToInt(FrameAddrPtr, IntptrTy);
-    auto LowestStack = IRB.CreateLoad(IntptrTy, SanCovLowestStack);
-    auto IsStackLower = IRB.CreateICmpULT(FrameAddrInt, LowestStack);
-    auto ThenTerm = SplitBlockAndInsertIfThen(
-        IsStackLower, &*IP, false,
-        MDBuilder(IRB.getContext()).createUnlikelyBranchWeights());
-    IRBuilder<> ThenIRB(ThenTerm);
-    auto Store = ThenIRB.CreateStore(FrameAddrInt, SanCovLowestStack);
-    LowestStack->setNoSanitizeMetadata();
-    Store->setNoSanitizeMetadata();
+    const DataLayout &DL = M->getDataLayout();
+
+    if (Options.StackDepthCallbackMin) {
+      // In callback mode, only add call when stack depth reaches minimum.
+      uint32_t EstimatedStackSize = 0;
+      // If dynamic alloca found, always add call.
+      bool dynamic_alloca = false;
----------------
melver wrote:

HasDynamicAlloc?

https://github.com/llvm/llvm-project/pull/138323