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_arm64.cc b/compiler/optimizing/code_generator_arm64.cc
index 11de4ee..bbde7e8 100644
--- a/compiler/optimizing/code_generator_arm64.cc
+++ b/compiler/optimizing/code_generator_arm64.cc
@@ -2496,6 +2496,10 @@
}
}
+static MemOperand GetExceptionTlsAddress() {
+ return MemOperand(tr, Thread::ExceptionOffset<kArm64WordSize>().Int32Value());
+}
+
void LocationsBuilderARM64::VisitLoadException(HLoadException* load) {
LocationSummary* locations =
new (GetGraph()->GetArena()) LocationSummary(load, LocationSummary::kNoCall);
@@ -2503,9 +2507,15 @@
}
void InstructionCodeGeneratorARM64::VisitLoadException(HLoadException* instruction) {
- MemOperand exception = MemOperand(tr, Thread::ExceptionOffset<kArm64WordSize>().Int32Value());
- __ Ldr(OutputRegister(instruction), exception);
- __ Str(wzr, exception);
+ __ Ldr(OutputRegister(instruction), GetExceptionTlsAddress());
+}
+
+void LocationsBuilderARM64::VisitClearException(HClearException* clear) {
+ new (GetGraph()->GetArena()) LocationSummary(clear, LocationSummary::kNoCall);
+}
+
+void InstructionCodeGeneratorARM64::VisitClearException(HClearException* clear ATTRIBUTE_UNUSED) {
+ __ Str(wzr, GetExceptionTlsAddress());
}
void LocationsBuilderARM64::VisitLoadLocal(HLoadLocal* load) {