diff --git a/src/compile.cpp b/src/compile.cpp
index 402ed31896..437bb70790 100644
--- a/src/compile.cpp
+++ b/src/compile.cpp
@@ -163,6 +163,11 @@ methodForIp(MyThread* t, void* ip)
     fprintf(stderr, "query for method containing %p\n", ip);
   }
 
+  // we must use a version of the method tree at least as recent as the
+  // compiled form of the method containing the specified address (see
+  // compile(MyThread*, Allocator*, BootContext*, object)):
+  memoryBarrier();
+
   return treeQuery(t, methodTree(t), reinterpret_cast<intptr_t>(ip),
                    methodTreeSentinal(t), compareIpToMethodBounds);
 }
@@ -4189,11 +4194,7 @@ finish(MyThread* t, Allocator* allocator, Context* context)
        (&byteArrayBody(t, methodName(t, context->method), 0)),
        "printStackTrace") == 0)
   {
-#ifdef __POWERPC__
-    asm("trap");
-#else
-    asm("int3");
-#endif
+    trap();
   }
 
   return start;
@@ -5377,6 +5378,11 @@ findCallNode(MyThread* t, void* address)
     fprintf(stderr, "find call node %p\n", address);
   }
 
+  // we must use a version of the call table at least as recent as the
+  // compiled form of the method containing the specified address (see
+  // compile(MyThread*, Allocator*, BootContext*, object)):
+  memoryBarrier();
+
   MyProcessor* p = processor(t);
   object table = p->callTable;
 
@@ -5961,6 +5967,8 @@ compile(MyThread* t, Allocator* allocator, BootContext* bootContext,
          reinterpret_cast<intptr_t>(compiled), clone, methodTreeSentinal(t),
          compareIpToMethodBounds);
 
+      memoryBarrier();
+
       methodCompiled(t, method) = reinterpret_cast<intptr_t>(compiled);
 
       if (methodVirtual(t, method)) {
diff --git a/src/posix.cpp b/src/posix.cpp
index 18b38cca99..42a66f2b48 100644
--- a/src/posix.cpp
+++ b/src/posix.cpp
@@ -790,6 +790,10 @@ handleSignal(int signal, siginfo_t* info, void* context)
 {
   ucontext_t* c = static_cast<ucontext_t*>(context);
 
+#ifndef BASE_REGISTER
+#  define BASE_REGISTER(x) 0
+#endif
+
   void* ip = reinterpret_cast<void*>(IP_REGISTER(c));
   void* base = reinterpret_cast<void*>(BASE_REGISTER(c));
   void* stack = reinterpret_cast<void*>(STACK_REGISTER(c));
diff --git a/src/powerpc.h b/src/powerpc.h
index 00e5488f4e..feb6c7b285 100644
--- a/src/powerpc.h
+++ b/src/powerpc.h
@@ -17,20 +17,17 @@
 #ifdef __APPLE__
 #  if __DARWIN_UNIX03 && defined(_STRUCT_X86_EXCEPTION_STATE32)
 #    define IP_REGISTER(context) (context->uc_mcontext->__ss.__srr0)
-#    define BASE_REGISTER(context) (context->uc_mcontext->__ss.__r13)
 #    define STACK_REGISTER(context) (context->uc_mcontext->__ss.__r1)
-#    define THREAD_REGISTER(context) (context->uc_mcontext->__ss.__r14)
+#    define THREAD_REGISTER(context) (context->uc_mcontext->__ss.__r13)
 #  else
 #    define IP_REGISTER(context) (context->uc_mcontext->ss.srr0)
-#    define BASE_REGISTER(context) (context->uc_mcontext->ss.r13)
 #    define STACK_REGISTER(context) (context->uc_mcontext->ss.r1)
-#    define THREAD_REGISTER(context) (context->uc_mcontext->ss.r14)
+#    define THREAD_REGISTER(context) (context->uc_mcontext->ss.r13)
 #  endif
 #else
 #  define IP_REGISTER(context) (context->uc_mcontext.gregs[32])
-#  define BASE_REGISTER(context) (context->uc_mcontext.gregs[13])
 #  define STACK_REGISTER(context) (context->uc_mcontext.gregs[1])
-#  define THREAD_REGISTER(context) (context->uc_mcontext.gregs[14])
+#  define THREAD_REGISTER(context) (context->uc_mcontext.gregs[13])
 #endif
 
 extern "C" uint64_t
@@ -40,6 +37,18 @@ vmNativeCall(void* function, unsigned stackTotal, void* memoryTable,
 
 namespace vm {
 
+inline void
+trap()
+{
+  asm("trap");
+}
+
+inline void
+memoryBarrier()
+{
+  __asm__ __volatile__("sync": : :"memory");
+}
+
 inline uint64_t
 dynamicCall(void* function, uintptr_t* arguments, uint8_t* argumentTypes,
             unsigned argumentCount, unsigned argumentsSize,
diff --git a/src/x86.h b/src/x86.h
index ae56473882..71d84e140c 100644
--- a/src/x86.h
+++ b/src/x86.h
@@ -41,6 +41,18 @@ vmNativeCall(void* function, void* stack, unsigned stackSize,
 
 namespace vm {
 
+inline void
+trap()
+{
+  asm("int3");
+}
+
+inline void
+memoryBarrier()
+{
+  __asm__ __volatile__("": : :"memory");
+}
+
 inline uint64_t
 dynamicCall(void* function, uintptr_t* arguments, uint8_t*,
             unsigned, unsigned argumentsSize, unsigned returnType)