diff --git a/compiler-rt/lib/gwp_asan/guarded_pool_allocator.cpp b/compiler-rt/lib/gwp_asan/guarded_pool_allocator.cpp
--- a/compiler-rt/lib/gwp_asan/guarded_pool_allocator.cpp
+++ b/compiler-rt/lib/gwp_asan/guarded_pool_allocator.cpp
@@ -258,7 +258,10 @@
   // Raise a SEGV by touching first guard page.
   volatile char *p = reinterpret_cast<char *>(State.GuardedPagePool);
   *p = 0;
-  __builtin_unreachable();
+  // Normally, would be __builtin_unreachable(), but because of
+  // https://bugs.llvm.org/show_bug.cgi?id=47480, unreachable will DCE the
+  // volatile store above, even though it has side effects.
+  __builtin_trap();
 }
 
 void GuardedPoolAllocator::stop() {