[compiler-rt] [llvm] [compiler-rt][asan] Add asan checks for __builtin_assume_dereferencable (PR #190871)

[Florian Mayer via llvm-commits]

================
@@ -3189,6 +3209,28 @@ bool AddressSanitizer::instrumentFunction(Function &F,
     FunctionModified = true;
   }
 
+  for (auto *AI : DerefAssumptions) {
+    if (auto Bundle = AI->getOperandBundle("dereferenceable")) {
+      Value *Ptr = Bundle->Inputs[0];
+      Value *Size = Bundle->Inputs[1];
+
+      InstrumentationIRBuilder IRB(AI);
+      Value *AddrLong = IRB.CreatePointerCast(Ptr, IntptrTy);
+      Value *SizeExt = IRB.CreateZExtOrTrunc(Size, IntptrTy);
+
+      // Skip if size is exactly 0.
+      if (ConstantInt *CI = dyn_cast<ConstantInt>(SizeExt)) {
----------------
fmayer wrote:

Can we do this check without using IRB? otherwise we are inserting casts and then ignoring them.

https://github.com/llvm/llvm-project/pull/190871