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/code_generator_x86.cc b/compiler/optimizing/code_generator_x86.cc
index 0569565..fdef06b 100644
--- a/compiler/optimizing/code_generator_x86.cc
+++ b/compiler/optimizing/code_generator_x86.cc
@@ -4693,6 +4693,10 @@
__ Bind(slow_path->GetExitLabel());
}
+static Address GetExceptionTlsAddress() {
+ return Address::Absolute(Thread::ExceptionOffset<kX86WordSize>().Int32Value());
+}
+
void LocationsBuilderX86::VisitLoadException(HLoadException* load) {
LocationSummary* locations =
new (GetGraph()->GetArena()) LocationSummary(load, LocationSummary::kNoCall);
@@ -4700,9 +4704,15 @@
}
void InstructionCodeGeneratorX86::VisitLoadException(HLoadException* load) {
- Address address = Address::Absolute(Thread::ExceptionOffset<kX86WordSize>().Int32Value());
- __ fs()->movl(load->GetLocations()->Out().AsRegister<Register>(), address);
- __ fs()->movl(address, Immediate(0));
+ __ fs()->movl(load->GetLocations()->Out().AsRegister<Register>(), GetExceptionTlsAddress());
+}
+
+void LocationsBuilderX86::VisitClearException(HClearException* clear) {
+ new (GetGraph()->GetArena()) LocationSummary(clear, LocationSummary::kNoCall);
+}
+
+void InstructionCodeGeneratorX86::VisitClearException(HClearException* clear ATTRIBUTE_UNUSED) {
+ __ fs()->movl(GetExceptionTlsAddress(), Immediate(0));
}
void LocationsBuilderX86::VisitThrow(HThrow* instruction) {