ART: Add option to ensure deterministic compilation
To ensure reliable stable generation of a boot image, add a flag
for forced determinism, trading compile time for a deterministic
output.
We have to run certain passes in the compiler-driver single-threaded.
It is also necessary to try to make the heap layout deterministic.
Switch to nonconcurrent GC, use the free-list implementation for LOS,
and try to allocate the main space at a known location. This is best
effort at the moment.
To allow the compiler phase to be parallelized, const-strings need
to be created beforehand.
The identity hashcode seed needs to be pinned.
Besides the Dex object we also need to null the DexFile pointer in
dex caches.
For classes, we need to remove the clinit thread ID.
Fix oatdump alignment padding accounting.
Bug: 26687569
Change-Id: Ia82120e8f715bb3691d861817b12778ac677355a
diff --git a/runtime/gc/heap.cc b/runtime/gc/heap.cc
index 8cd8d73..5bb7cf3 100644
--- a/runtime/gc/heap.cc
+++ b/runtime/gc/heap.cc
@@ -114,6 +114,9 @@
// timeout on how long we wait for finalizers to run. b/21544853
static constexpr uint64_t kNativeAllocationFinalizeTimeout = MsToNs(250u);
+// For deterministic compilation, we need the heap to be at a well-known address.
+static constexpr uint32_t kAllocSpaceBeginForDeterministicAoT = 0x40000000;
+
Heap::Heap(size_t initial_size,
size_t growth_limit,
size_t min_free,
@@ -352,6 +355,11 @@
}
std::unique_ptr<MemMap> main_mem_map_1;
std::unique_ptr<MemMap> main_mem_map_2;
+
+ // Gross hack to make dex2oat deterministic.
+ if (requested_alloc_space_begin == nullptr && Runtime::Current()->IsAotCompiler()) {
+ requested_alloc_space_begin = reinterpret_cast<uint8_t*>(kAllocSpaceBeginForDeterministicAoT);
+ }
uint8_t* request_begin = requested_alloc_space_begin;
if (request_begin != nullptr && separate_non_moving_space) {
request_begin += non_moving_space_capacity;