fix Avian_sun_misc_Unsafe_compareAndSwapLong for platforms without atomicCompareAndSwap64

We never define atomicCompareAndSwap64 for ARM or PowerPC, and
apparently only very recent ARM chips support it, so we must fall back
to synchronization-based emulation.

makefile

@@ -246,7 +246,8 @@ ifeq ($(arch),arm)
 	ifeq ($(build-platform),darwin)
 		ios = true
 	else
-		cflags += -marm -Wno-psabi
+		no-psabi = -Wno-psabi
+		cflags += -marm $(no-psabi)
 	endif
 
 	ifneq ($(arch),$(build-arch))
@@ -586,6 +587,8 @@ endif
 cflags += $(extra-cflags)
 lflags += $(extra-lflags)
 
+openjdk-cflags += $(extra-cflags)
+
 driver-source = $(src)/main.cpp
 driver-object = $(build)/main.o
 driver-dynamic-objects = \

src/classpath-openjdk.cpp

@@ -2594,15 +2594,25 @@ Avian_sun_misc_Unsafe_compareAndSwapObject
 
 extern "C" JNIEXPORT int64_t JNICALL
 Avian_sun_misc_Unsafe_compareAndSwapLong
-(Thread*, object, uintptr_t* arguments)
+(Thread* t UNUSED, object, uintptr_t* arguments)
 {
   object target = reinterpret_cast<object>(arguments[1]);
   int64_t offset; memcpy(&offset, arguments + 2, 8);
   uint64_t expect; memcpy(&expect, arguments + 4, 8);
   uint64_t update; memcpy(&update, arguments + 6, 8);
 
+#ifdef AVIAN_HAS_CAS64
   return atomicCompareAndSwap64
     (&cast<uint64_t>(target, offset), expect, update);
+#else
+  ACQUIRE_FIELD_FOR_WRITE(t, local::fieldForOffset(t, target, offset));
+  if (cast<uint64_t>(target, offset) == expect) {
+    cast<uint64_t>(target, offset) = update;
+    return true;
+  } else {
+    return false;
+  }
+#endif
 }
 
 extern "C" JNIEXPORT int64_t JNICALL

src/x86.h

@@ -255,6 +255,8 @@ atomicCompareAndSwap32(uint32_t* p, uint32_t old, uint32_t new_)
 #endif
 }
 
+#define AVIAN_HAS_CAS64
+
 inline bool
 atomicCompareAndSwap64(uint64_t* p, uint64_t old, uint64_t new_)
 {