X86: Use memory to do array range checks
Currently, an HBoundsCheck is fed by an HArrayLength, causing a load of
the array length, followed by a register compare.
Avoid the load when we can by comparing directly with the array length
in memory. Implement this by marking the HArrayLength as 'emitted at
use site', and then generating the code in the HBoundsCheck.
Only do this replacement when we are the only user of the ArrayLength
and it isn't visible to the environment.
Handle the special case where the array is 'null' and where an implicit
null check can't be eliminated.
This code moves the load of the length to the slow code for the failed
check, which is what we want.
Test: 609-checker-x86-bounds-check
Change-Id: I9cdb183301e048234bb0ffeda940eedcf4a655bd
Signed-off-by: Mark Mendell <mark.p.mendell@intel.com>
diff --git a/compiler/optimizing/code_generator_x86.cc b/compiler/optimizing/code_generator_x86.cc
index be20f1f..7f39661 100644
--- a/compiler/optimizing/code_generator_x86.cc
+++ b/compiler/optimizing/code_generator_x86.cc
@@ -140,12 +140,29 @@
// Live registers will be restored in the catch block if caught.
SaveLiveRegisters(codegen, instruction_->GetLocations());
}
+
+ // Are we using an array length from memory?
+ HInstruction* array_length = instruction_->InputAt(1);
+ Location length_loc = locations->InAt(1);
InvokeRuntimeCallingConvention calling_convention;
+ if (array_length->IsArrayLength() && array_length->IsEmittedAtUseSite()) {
+ // Load the array length into our temporary.
+ uint32_t len_offset = CodeGenerator::GetArrayLengthOffset(array_length->AsArrayLength());
+ Location array_loc = array_length->GetLocations()->InAt(0);
+ Address array_len(array_loc.AsRegister<Register>(), len_offset);
+ length_loc = Location::RegisterLocation(calling_convention.GetRegisterAt(1));
+ // Check for conflicts with index.
+ if (length_loc.Equals(locations->InAt(0))) {
+ // We know we aren't using parameter 2.
+ length_loc = Location::RegisterLocation(calling_convention.GetRegisterAt(2));
+ }
+ __ movl(length_loc.AsRegister<Register>(), array_len);
+ }
x86_codegen->EmitParallelMoves(
locations->InAt(0),
Location::RegisterLocation(calling_convention.GetRegisterAt(0)),
Primitive::kPrimInt,
- locations->InAt(1),
+ length_loc,
Location::RegisterLocation(calling_convention.GetRegisterAt(1)),
Primitive::kPrimInt);
uint32_t entry_point_offset = instruction_->AsBoundsCheck()->IsStringCharAt()
@@ -5517,10 +5534,16 @@
void LocationsBuilderX86::VisitArrayLength(HArrayLength* instruction) {
LocationSummary* locations = new (GetGraph()->GetArena()) LocationSummary(instruction);
locations->SetInAt(0, Location::RequiresRegister());
- locations->SetOut(Location::RequiresRegister(), Location::kNoOutputOverlap);
+ if (!instruction->IsEmittedAtUseSite()) {
+ locations->SetOut(Location::RequiresRegister(), Location::kNoOutputOverlap);
+ }
}
void InstructionCodeGeneratorX86::VisitArrayLength(HArrayLength* instruction) {
+ if (instruction->IsEmittedAtUseSite()) {
+ return;
+ }
+
LocationSummary* locations = instruction->GetLocations();
uint32_t offset = CodeGenerator::GetArrayLengthOffset(instruction);
Register obj = locations->InAt(0).AsRegister<Register>();
@@ -5535,7 +5558,10 @@
: LocationSummary::kNoCall;
LocationSummary* locations = new (GetGraph()->GetArena()) LocationSummary(instruction, call_kind);
locations->SetInAt(0, Location::RegisterOrConstant(instruction->InputAt(0)));
- locations->SetInAt(1, Location::RegisterOrConstant(instruction->InputAt(1)));
+ HInstruction* length = instruction->InputAt(1);
+ if (!length->IsEmittedAtUseSite()) {
+ locations->SetInAt(1, Location::RegisterOrConstant(instruction->InputAt(1)));
+ }
if (instruction->HasUses()) {
locations->SetOut(Location::SameAsFirstInput());
}
@@ -5569,12 +5595,28 @@
codegen_->AddSlowPath(slow_path);
__ j(kAboveEqual, slow_path->GetEntryLabel());
} else {
- Register length = length_loc.AsRegister<Register>();
- if (index_loc.IsConstant()) {
- int32_t value = CodeGenerator::GetInt32ValueOf(index_loc.GetConstant());
- __ cmpl(length, Immediate(value));
+ HInstruction* array_length = instruction->InputAt(1);
+ if (array_length->IsEmittedAtUseSite()) {
+ // Address the length field in the array.
+ DCHECK(array_length->IsArrayLength());
+ uint32_t len_offset = CodeGenerator::GetArrayLengthOffset(array_length->AsArrayLength());
+ Location array_loc = array_length->GetLocations()->InAt(0);
+ Address array_len(array_loc.AsRegister<Register>(), len_offset);
+ if (index_loc.IsConstant()) {
+ int32_t value = CodeGenerator::GetInt32ValueOf(index_loc.GetConstant());
+ __ cmpl(array_len, Immediate(value));
+ } else {
+ __ cmpl(array_len, index_loc.AsRegister<Register>());
+ }
+ codegen_->MaybeRecordImplicitNullCheck(array_length);
} else {
- __ cmpl(length, index_loc.AsRegister<Register>());
+ Register length = length_loc.AsRegister<Register>();
+ if (index_loc.IsConstant()) {
+ int32_t value = CodeGenerator::GetInt32ValueOf(index_loc.GetConstant());
+ __ cmpl(length, Immediate(value));
+ } else {
+ __ cmpl(length, index_loc.AsRegister<Register>());
+ }
}
codegen_->AddSlowPath(slow_path);
__ j(kBelowEqual, slow_path->GetEntryLabel());