Revert "Revert "ART: Reduce the instructions generated by packed switch.""
This reverts commit b4c137630fd2226ad07dfd178ab15725374220f1.
The underlying issue was fixed by https://android-review.googlesource.com/188271 .
Bug: 26121945
Change-Id: I58b08eb1a9f0a5c861f8cda93522af64bcf63920
diff --git a/compiler/optimizing/code_generator_x86.cc b/compiler/optimizing/code_generator_x86.cc
index 2fb87d3..19f03df 100644
--- a/compiler/optimizing/code_generator_x86.cc
+++ b/compiler/optimizing/code_generator_x86.cc
@@ -42,7 +42,6 @@
static constexpr int kCurrentMethodStackOffset = 0;
static constexpr Register kMethodRegisterArgument = EAX;
-
static constexpr Register kCoreCalleeSaves[] = { EBP, ESI, EDI };
static constexpr int kC2ConditionMask = 0x400;
@@ -6426,31 +6425,67 @@
locations->SetInAt(0, Location::RequiresRegister());
}
-void InstructionCodeGeneratorX86::VisitPackedSwitch(HPackedSwitch* switch_instr) {
- int32_t lower_bound = switch_instr->GetStartValue();
- int32_t num_entries = switch_instr->GetNumEntries();
- LocationSummary* locations = switch_instr->GetLocations();
- Register value_reg = locations->InAt(0).AsRegister<Register>();
- HBasicBlock* default_block = switch_instr->GetDefaultBlock();
+void InstructionCodeGeneratorX86::GenPackedSwitchWithCompares(Register value_reg,
+ int32_t lower_bound,
+ uint32_t num_entries,
+ HBasicBlock* switch_block,
+ HBasicBlock* default_block) {
+ // Figure out the correct compare values and jump conditions.
+ // Handle the first compare/branch as a special case because it might
+ // jump to the default case.
+ DCHECK_GT(num_entries, 2u);
+ Condition first_condition;
+ uint32_t index;
+ const ArenaVector<HBasicBlock*>& successors = switch_block->GetSuccessors();
+ if (lower_bound != 0) {
+ first_condition = kLess;
+ __ cmpl(value_reg, Immediate(lower_bound));
+ __ j(first_condition, codegen_->GetLabelOf(default_block));
+ __ j(kEqual, codegen_->GetLabelOf(successors[0]));
- // Create a series of compare/jumps.
- const ArenaVector<HBasicBlock*>& successors = switch_instr->GetBlock()->GetSuccessors();
- for (int i = 0; i < num_entries; i++) {
- int32_t case_value = lower_bound + i;
- if (case_value == 0) {
- __ testl(value_reg, value_reg);
- } else {
- __ cmpl(value_reg, Immediate(case_value));
- }
- __ j(kEqual, codegen_->GetLabelOf(successors[i]));
+ index = 1;
+ } else {
+ // Handle all the compare/jumps below.
+ first_condition = kBelow;
+ index = 0;
+ }
+
+ // Handle the rest of the compare/jumps.
+ for (; index + 1 < num_entries; index += 2) {
+ int32_t compare_to_value = lower_bound + index + 1;
+ __ cmpl(value_reg, Immediate(compare_to_value));
+ // Jump to successors[index] if value < case_value[index].
+ __ j(first_condition, codegen_->GetLabelOf(successors[index]));
+ // Jump to successors[index + 1] if value == case_value[index + 1].
+ __ j(kEqual, codegen_->GetLabelOf(successors[index + 1]));
+ }
+
+ if (index != num_entries) {
+ // There are an odd number of entries. Handle the last one.
+ DCHECK_EQ(index + 1, num_entries);
+ __ cmpl(value_reg, Immediate(lower_bound + index));
+ __ j(kEqual, codegen_->GetLabelOf(successors[index]));
}
// And the default for any other value.
- if (!codegen_->GoesToNextBlock(switch_instr->GetBlock(), default_block)) {
- __ jmp(codegen_->GetLabelOf(default_block));
+ if (!codegen_->GoesToNextBlock(switch_block, default_block)) {
+ __ jmp(codegen_->GetLabelOf(default_block));
}
}
+void InstructionCodeGeneratorX86::VisitPackedSwitch(HPackedSwitch* switch_instr) {
+ int32_t lower_bound = switch_instr->GetStartValue();
+ uint32_t num_entries = switch_instr->GetNumEntries();
+ LocationSummary* locations = switch_instr->GetLocations();
+ Register value_reg = locations->InAt(0).AsRegister<Register>();
+
+ GenPackedSwitchWithCompares(value_reg,
+ lower_bound,
+ num_entries,
+ switch_instr->GetBlock(),
+ switch_instr->GetDefaultBlock());
+}
+
void LocationsBuilderX86::VisitX86PackedSwitch(HX86PackedSwitch* switch_instr) {
LocationSummary* locations =
new (GetGraph()->GetArena()) LocationSummary(switch_instr, LocationSummary::kNoCall);
@@ -6465,11 +6500,20 @@
void InstructionCodeGeneratorX86::VisitX86PackedSwitch(HX86PackedSwitch* switch_instr) {
int32_t lower_bound = switch_instr->GetStartValue();
- int32_t num_entries = switch_instr->GetNumEntries();
+ uint32_t num_entries = switch_instr->GetNumEntries();
LocationSummary* locations = switch_instr->GetLocations();
Register value_reg = locations->InAt(0).AsRegister<Register>();
HBasicBlock* default_block = switch_instr->GetDefaultBlock();
+ if (num_entries <= kPackedSwitchJumpTableThreshold) {
+ GenPackedSwitchWithCompares(value_reg,
+ lower_bound,
+ num_entries,
+ switch_instr->GetBlock(),
+ default_block);
+ return;
+ }
+
// Optimizing has a jump area.
Register temp_reg = locations->GetTemp(0).AsRegister<Register>();
Register constant_area = locations->InAt(1).AsRegister<Register>();
@@ -6481,7 +6525,7 @@
}
// Is the value in range?
- DCHECK_GE(num_entries, 1);
+ DCHECK_GE(num_entries, 1u);
__ cmpl(value_reg, Immediate(num_entries - 1));
__ j(kAbove, codegen_->GetLabelOf(default_block));