commit f60c90ba8d1eee6f137a9e1a8a65e4d6bec35d6d
author Mark Mendell <mark.p.mendell@intel.com> Wed Mar 04 15:12:59 2015 -0500
committer Mark Mendell <mark.p.mendell@intel.com> Wed Mar 04 15:17:09 2015 -0500
tree c0c41ae585ceb66c237a08e3ee8ce206920e9dee
parent ff3ef43f3d0f0986fe23286af028b352277b6e1e

[optimizing] Improve x86/x86_64 bound check code

Don't force a constant index into a register just to compare to the
array size.  Allow a constant, and compare the constant to the size.

Change-Id: I1c5732fbd42e63f7eac5c6219a19e9c431c22664
Signed-off-by: Mark Mendell <mark.p.mendell@intel.com>

compiler/optimizing/code_generator_x86_64.cc

diff --git a/compiler/optimizing/code_generator_x86_64.cc b/compiler/optimizing/code_generator_x86_64.cc
index 6365bca..e7e6fff 100644
--- a/compiler/optimizing/code_generator_x86_64.cc
+++ b/compiler/optimizing/code_generator_x86_64.cc
@@ -3164,7 +3164,7 @@
 void LocationsBuilderX86_64::VisitBoundsCheck(HBoundsCheck* instruction) {
   LocationSummary* locations =
       new (GetGraph()->GetArena()) LocationSummary(instruction, LocationSummary::kNoCall);
-  locations->SetInAt(0, Location::RequiresRegister());
+  locations->SetInAt(0, Location::RegisterOrConstant(instruction->InputAt(0)));
   locations->SetInAt(1, Location::RequiresRegister());
   if (instruction->HasUses()) {
     locations->SetOut(Location::SameAsFirstInput());
@@ -3173,15 +3173,20 @@
 
 void InstructionCodeGeneratorX86_64::VisitBoundsCheck(HBoundsCheck* instruction) {
   LocationSummary* locations = instruction->GetLocations();
-  SlowPathCodeX86_64* slow_path = new (GetGraph()->GetArena()) BoundsCheckSlowPathX86_64(
-      instruction, locations->InAt(0), locations->InAt(1));
+  Location index_loc = locations->InAt(0);
+  Location length_loc = locations->InAt(1);
+  SlowPathCodeX86_64* slow_path =
+    new (GetGraph()->GetArena()) BoundsCheckSlowPathX86_64(instruction, index_loc, length_loc);
   codegen_->AddSlowPath(slow_path);
 
-  CpuRegister index = locations->InAt(0).AsRegister<CpuRegister>();
-  CpuRegister length = locations->InAt(1).AsRegister<CpuRegister>();
-
-  __ cmpl(index, length);
-  __ j(kAboveEqual, slow_path->GetEntryLabel());
+  CpuRegister length = length_loc.AsRegister<CpuRegister>();
+  if (index_loc.IsConstant()) {
+    int32_t value = CodeGenerator::GetInt32ValueOf(index_loc.GetConstant());
+    __ cmpl(length, Immediate(value));
+  } else {
+    __ cmpl(length, index_loc.AsRegister<CpuRegister>());
+  }
+  __ j(kBelowEqual, slow_path->GetEntryLabel());
 }
 
 void CodeGeneratorX86_64::MarkGCCard(CpuRegister temp,