Deoptimization-based bce.
A mechanism is introduced that a runtime method can be called
from code compiled with optimizing compiler to deoptimize into
interpreter. This can be used to establish invariants in the managed code
If the invariant does not hold at runtime, we will deoptimize and continue
execution in the interpreter. This allows to optimize the managed code as
if the invariant was proven during compile time. However, the exception
will be thrown according to the semantics demanded by the spec.
The invariant and optimization included in this patch are based on the
length of an array. Given a set of array accesses with constant indices
{c1, ..., cn}, we can optimize away all bounds checks iff all 0 <= min(ci) and
max(ci) < array-length. The first can be proven statically. The second can be
established with a deoptimization-based invariant. This replaces n bounds
checks with one invariant check (plus slow-path code).
Change-Id: I8c6e34b56c85d25b91074832d13dba1db0a81569
diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index 07ff8ba..b10231e 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -616,6 +616,7 @@
M(ClinitCheck, Instruction) \
M(Compare, BinaryOperation) \
M(Condition, BinaryOperation) \
+ M(Deoptimize, Instruction) \
M(Div, BinaryOperation) \
M(DivZeroCheck, Instruction) \
M(DoubleConstant, Constant) \
@@ -1478,12 +1479,31 @@
DECLARE_INSTRUCTION(If);
- virtual bool IsIfInstruction() const { return true; }
-
private:
DISALLOW_COPY_AND_ASSIGN(HIf);
};
+// Deoptimize to interpreter, upon checking a condition.
+class HDeoptimize : public HTemplateInstruction<1> {
+ public:
+ HDeoptimize(HInstruction* cond, uint32_t dex_pc)
+ : HTemplateInstruction(SideEffects::None()),
+ dex_pc_(dex_pc) {
+ SetRawInputAt(0, cond);
+ }
+
+ bool NeedsEnvironment() const OVERRIDE { return true; }
+ bool CanThrow() const OVERRIDE { return true; }
+ uint32_t GetDexPc() const { return dex_pc_; }
+
+ DECLARE_INSTRUCTION(Deoptimize);
+
+ private:
+ uint32_t dex_pc_;
+
+ DISALLOW_COPY_AND_ASSIGN(HDeoptimize);
+};
+
class HUnaryOperation : public HExpression<1> {
public:
HUnaryOperation(Primitive::Type result_type, HInstruction* input)
@@ -1601,8 +1621,8 @@
void ClearNeedsMaterialization() { needs_materialization_ = false; }
// For code generation purposes, returns whether this instruction is just before
- // `if_`, and disregard moves in between.
- bool IsBeforeWhenDisregardMoves(HIf* if_) const;
+ // `instruction`, and disregard moves in between.
+ bool IsBeforeWhenDisregardMoves(HInstruction* instruction) const;
DECLARE_INSTRUCTION(Condition);