Class Hierarchy Analysis (CHA)
The class linker now tracks whether a method has a single implementation
and if so, the JIT compiler will try to devirtualize a virtual call for
the method into a direct call. If the single-implementation assumption
is violated due to additional class linking, compiled code that makes the
assumption is invalidated. Deoptimization is triggered for compiled code
live on stack. Instead of patching return pc's on stack, a CHA guard is
added which checks a hidden should_deoptimize flag for deoptimization.
This approach limits the number of deoptimization points.
This CL does not devirtualize abstract/interface method invocation.
Slides on CHA:
https://docs.google.com/a/google.com/presentation/d/1Ax6cabP1vM44aLOaJU3B26n5fTE9w5YU-1CRevIDsBc/edit?usp=sharing
Change-Id: I18bf716a601b6413b46312e925a6ad9e4008efa4
Test: ART_TEST_JIT=true m test-art-host/target-run-test test-art-host-gtest
diff --git a/runtime/oat_quick_method_header.h b/runtime/oat_quick_method_header.h
index 4afca7d..3cdde5a 100644
--- a/runtime/oat_quick_method_header.h
+++ b/runtime/oat_quick_method_header.h
@@ -58,7 +58,7 @@
}
bool IsOptimized() const {
- return code_size_ != 0 && vmap_table_offset_ != 0;
+ return GetCodeSize() != 0 && vmap_table_offset_ != 0;
}
const void* GetOptimizedCodeInfoPtr() const {
@@ -81,7 +81,23 @@
}
uint32_t GetCodeSize() const {
- return code_size_;
+ return code_size_ & kCodeSizeMask;
+ }
+
+ const uint32_t* GetCodeSizeAddr() const {
+ return &code_size_;
+ }
+
+ uint32_t GetVmapTableOffset() const {
+ return vmap_table_offset_;
+ }
+
+ void SetVmapTableOffset(uint32_t offset) {
+ vmap_table_offset_ = offset;
+ }
+
+ const uint32_t* GetVmapTableOffsetAddr() const {
+ return &vmap_table_offset_;
}
const uint8_t* GetVmapTable() const {
@@ -96,7 +112,7 @@
// On Thumb-2, the pc is offset by one.
code_start++;
}
- return code_start <= pc && pc <= (code_start + code_size_);
+ return code_start <= pc && pc <= (code_start + GetCodeSize());
}
const uint8_t* GetEntryPoint() const {
@@ -130,11 +146,25 @@
uint32_t ToDexPc(ArtMethod* method, const uintptr_t pc, bool abort_on_failure = true) const;
+ void SetHasShouldDeoptimizeFlag() {
+ DCHECK_EQ(code_size_ & kShouldDeoptimizeMask, 0u);
+ code_size_ |= kShouldDeoptimizeMask;
+ }
+
+ bool HasShouldDeoptimizeFlag() const {
+ return (code_size_ & kShouldDeoptimizeMask) != 0;
+ }
+
+ private:
+ static constexpr uint32_t kShouldDeoptimizeMask = 0x80000000;
+ static constexpr uint32_t kCodeSizeMask = ~kShouldDeoptimizeMask;
+
// The offset in bytes from the start of the vmap table to the end of the header.
uint32_t vmap_table_offset_;
// The stack frame information.
QuickMethodFrameInfo frame_info_;
- // The code size in bytes.
+ // The code size in bytes. The highest bit is used to signify if the compiled
+ // code with the method header has should_deoptimize flag.
uint32_t code_size_;
// The actual code.
uint8_t code_[0];