x86/x86-64 read barrier support for concurrent GC in Optimizing.
This first implementation uses slow paths to instrument heap
reference loads and GC root loads for the concurrent copying
collector, respectively calling the artReadBarrierSlow and
artReadBarrierForRootSlow (new) runtime entry points.
Notes:
- This implementation does not instrument HInvokeVirtual
nor HInvokeInterface instructions (for class reference
loads), as the corresponding read barriers are not stricly
required with the current concurrent copying collector.
- Intrinsics which may eventually call (on slow path) are
disabled when read barriers are enabled, as the current
slow path infrastructure does not support this case.
- When read barriers are enabled, the code generated for a
HArraySet instruction always go into the array set slow
path for object arrays (delegating the operation to the
runtime), as we are lacking a mechanism to keep a
temporary register live accross a runtime call (needed for
the instrumentation of type checking code, which requires
two successive read barriers).
Bug: 12687968
Change-Id: I14cd6107233c326389120336f93955b28ffbb329
diff --git a/compiler/optimizing/code_generator_x86.h b/compiler/optimizing/code_generator_x86.h
index 177a059..cd606f6 100644
--- a/compiler/optimizing/code_generator_x86.h
+++ b/compiler/optimizing/code_generator_x86.h
@@ -397,6 +397,51 @@
void Finalize(CodeAllocator* allocator) OVERRIDE;
+ // Generate a read barrier for a heap reference within `instruction`.
+ //
+ // A read barrier for an object reference read from the heap is
+ // implemented as a call to the artReadBarrierSlow runtime entry
+ // point, which is passed the values in locations `ref`, `obj`, and
+ // `offset`:
+ //
+ // mirror::Object* artReadBarrierSlow(mirror::Object* ref,
+ // mirror::Object* obj,
+ // uint32_t offset);
+ //
+ // The `out` location contains the value returned by
+ // artReadBarrierSlow.
+ //
+ // When `index` is provided (i.e. for array accesses), the offset
+ // value passed to artReadBarrierSlow is adjusted to take `index`
+ // into account.
+ void GenerateReadBarrier(HInstruction* instruction,
+ Location out,
+ Location ref,
+ Location obj,
+ uint32_t offset,
+ Location index = Location::NoLocation());
+
+ // If read barriers are enabled, generate a read barrier for a heap reference.
+ // If heap poisoning is enabled, also unpoison the reference in `out`.
+ void MaybeGenerateReadBarrier(HInstruction* instruction,
+ Location out,
+ Location ref,
+ Location obj,
+ uint32_t offset,
+ Location index = Location::NoLocation());
+
+ // Generate a read barrier for a GC root within `instruction`.
+ //
+ // A read barrier for an object reference GC root is implemented as
+ // a call to the artReadBarrierForRootSlow runtime entry point,
+ // which is passed the value in location `root`:
+ //
+ // mirror::Object* artReadBarrierForRootSlow(GcRoot<mirror::Object>* root);
+ //
+ // The `out` location contains the value returned by
+ // artReadBarrierForRootSlow.
+ void GenerateReadBarrierForRoot(HInstruction* instruction, Location out, Location root);
+
private:
Register GetInvokeStaticOrDirectExtraParameter(HInvokeStaticOrDirect* invoke, Register temp);