ART: Move exception clearing into own instruction
Runtime delivers exceptions only to catch blocks which begin with a
MOVE_EXCEPTION instruction (in DEX). In that case, the catch block is
expected to clear the thread-local exception storage after having
read the exception reference.
This patch changes Optimizing to represent MOVE_EXCEPTION with two
instructions - HLoadException and HClearException - instead of one.
If the exception reference is not used, HLoadException can be safely
removed, saving a memory load without breaking the runtime behaviour.
Change-Id: Idad8a714467bf9d9d5fccefbc43c0bd8ae13ddba
diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index 9b8521d..638ac95 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -961,6 +961,7 @@
M(BoundsCheck, Instruction) \
M(BoundType, Instruction) \
M(CheckCast, Instruction) \
+ M(ClearException, Instruction) \
M(ClinitCheck, Instruction) \
M(Compare, BinaryOperation) \
M(Condition, BinaryOperation) \
@@ -4142,6 +4143,18 @@
DISALLOW_COPY_AND_ASSIGN(HLoadException);
};
+// Implicit part of move-exception which clears thread-local exception storage.
+// Must not be removed because the runtime expects the TLS to get cleared.
+class HClearException : public HTemplateInstruction<0> {
+ public:
+ HClearException() : HTemplateInstruction(SideEffects::AllWrites()) {}
+
+ DECLARE_INSTRUCTION(ClearException);
+
+ private:
+ DISALLOW_COPY_AND_ASSIGN(HClearException);
+};
+
class HThrow : public HTemplateInstruction<1> {
public:
HThrow(HInstruction* exception, uint32_t dex_pc)