diff --git a/llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn b/llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn
--- a/llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn
+++ b/llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn
@@ -329,7 +329,6 @@
     "LLVM_HAVE_TFLITE=",
     "LLVM_HOST_TRIPLE=$llvm_current_triple",
     "LLVM_NATIVE_ARCH=$native_target",
-    "LLVM_UNREACHABLE_OPTIMIZE=1",
     "LLVM_USE_INTEL_JITEVENTS=",
     "LLVM_USE_OPROFILE=",
     "LLVM_USE_PERF=",
@@ -340,6 +339,12 @@
     "PACKAGE_VERSION=${llvm_version}git",
   ]
 
+  if (llvm_enable_assertions) {
+    values += [ "LLVM_UNREACHABLE_OPTIMIZE=" ]
+  } else {
+    values += [ "LLVM_UNREACHABLE_OPTIMIZE=1" ]
+  }
+
   if (llvm_build_native) {
     values += [
       "LLVM_NATIVE_ASMPARSER=1",