[clang] [Clang] Make __builtin_assume_dereferenceable constexpr (PR #169869)

[Timm Baeder via cfe-commits]

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@@ -19690,6 +19690,35 @@ class VoidExprEvaluator
       // The argument is not evaluated!
       return true;
 
+    case Builtin::BI__builtin_assume_dereferenceable: {
+      assert(E->getType()->isVoidType());
+      assert(E->getNumArgs() == 2);
+
+      APSInt ReqSizeVal;
+      if (!::EvaluateInteger(E->getArg(1), ReqSizeVal, Info))
+        return false;
+      LValue Pointer;
+      if (!EvaluatePointer(E->getArg(0), Pointer, Info))
+        return false;
+      if (Pointer.Designator.Invalid)
+        return false;
+      if (Pointer.isNullPointer())
+        return false;
+
+      uint64_t ReqSize = ReqSizeVal.getZExtValue();
+      if (ReqSize < 1)
+        return false;
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tbaederr wrote:

Shouldn't this return true?

https://github.com/llvm/llvm-project/pull/169869