0xdeadbeef is used throughout the JVM. There is potential to consolidate this into a BAD_PTR macro as suggested by David Holmes in JDK-8196884. Assessment is needed to understand all the different conversions that exist when 0xdeadbeef is used to determine if they could all be safely converted to intptr_t.

os/aix/misc_aix.cpp: int deadbeef = 0xdeadbeef;
share/gc/cms/freeChunk.cpp:#define deadbeefHeapWord 0xdeadbeef
share/prims/jni.cpp: jint b = Atomic::xchg((jint) 0xdeadbeef, &a);
share/prims/jni.cpp: assert(a == (jint) 0xdeadbeef && b == (jint) 0xcafebabe, "Atomic::xchg() works");
share/opto/output.cpp: debug_only( def = (Node*)((intptr_t)0xdeadbeef); )
share/opto/regalloc.cpp: _framesize(0xdeadbeef)
share/opto/node.hpp: debug_only(_out[_outcnt] = (Node *)(uintptr_t)0xdeadbeef);
share/opto/node.hpp: debug_only(_out[_outcnt] = (Node *)(uintptr_t)0xdeadbeef);
share/opto/split_if.cpp: Node *prior_n = (Node*)((intptr_t)0xdeadbeef);
share/opto/split_if.cpp: prior_n = (Node*)((intptr_t)0xdeadbeef); // Reset IDOM walk
share/opto/idealGraphPrinter.cpp: if (_chaitin && _chaitin != (PhaseChaitin *)((intptr_t)0xdeadbeef)) {
share/opto/gcm.cpp: _node_latency = (GrowableArray<uint> *)((intptr_t)0xdeadbeef);
share/opto/buildOopMap.cpp: Block *pred = (Block*)((intptr_t)0xdeadbeef);
share/opto/compile.cpp: _cfg = (PhaseCFG*)((intptr_t)0xdeadbeef);
share/opto/compile.cpp: _regalloc = (PhaseChaitin*)((intptr_t)0xdeadbeef);
cpu/aarch64/stubGenerator_aarch64.cpp: __ mov(rscratch1, (uint64_t)0xdeadbeef);
cpu/s390/macroAssembler_s390.cpp: z_iilf(scratch, 0xdeadbeef);