Revert "ART: Removes SuspendCheck for plain loops with a low trip count."
This reverts commit 3de02fb67de386368c9fe39ab5a0133afcf1d785.
Reason for revert: b/201413752
Change-Id: I8a3a56cfb81fa88f49992615696260dfbc79bb67
diff --git a/compiler/optimizing/code_generator.cc b/compiler/optimizing/code_generator.cc
index cabf949..6b3ae41 100644
--- a/compiler/optimizing/code_generator.cc
+++ b/compiler/optimizing/code_generator.cc
@@ -1118,7 +1118,7 @@
for (HBasicBlock* block : graph.GetReversePostOrder()) {
if (block->IsLoopHeader()) {
HSuspendCheck* suspend_check = block->GetLoopInformation()->GetSuspendCheck();
- if (suspend_check != nullptr && !suspend_check->GetEnvironment()->IsFromInlinedInvoke()) {
+ if (!suspend_check->GetEnvironment()->IsFromInlinedInvoke()) {
loop_headers.push_back(suspend_check);
}
}
diff --git a/compiler/optimizing/graph_checker.cc b/compiler/optimizing/graph_checker.cc
index 55a505c..d1769ce 100644
--- a/compiler/optimizing/graph_checker.cc
+++ b/compiler/optimizing/graph_checker.cc
@@ -674,14 +674,13 @@
loop_information->GetPreHeader()->GetSuccessors().size()));
}
- if (!GetGraph()->SuspendChecksAreAllowedToBeRemoved() &&
- loop_information->GetSuspendCheck() == nullptr) {
- AddError(StringPrintf("Loop with header %d does not have a suspend check.",
- loop_header->GetBlockId()));
+ if (loop_information->GetSuspendCheck() == nullptr) {
+ AddError(StringPrintf(
+ "Loop with header %d does not have a suspend check.",
+ loop_header->GetBlockId()));
}
- if (!GetGraph()->SuspendChecksAreAllowedToBeRemoved() &&
- loop_information->GetSuspendCheck() != loop_header->GetFirstInstructionDisregardMoves()) {
+ if (loop_information->GetSuspendCheck() != loop_header->GetFirstInstructionDisregardMoves()) {
AddError(StringPrintf(
"Loop header %d does not have the loop suspend check as the first instruction.",
loop_header->GetBlockId()));
diff --git a/compiler/optimizing/loop_optimization.cc b/compiler/optimizing/loop_optimization.cc
index cd05482..02ee4ec 100644
--- a/compiler/optimizing/loop_optimization.cc
+++ b/compiler/optimizing/loop_optimization.cc
@@ -636,47 +636,6 @@
}
//
-// This optimization applies to loops with plain simple operations
-// (I.e. no calls to java code or runtime) with a known small trip_count * instr_count
-// value.
-//
-bool HLoopOptimization::TryToRemoveSuspendCheckFromLoopHeader(LoopAnalysisInfo* analysis_info,
- bool generate_code) {
- if (!graph_->SuspendChecksAreAllowedToBeRemoved()) {
- return false;
- }
-
- int64_t trip_count = analysis_info->GetTripCount();
-
- if (trip_count == LoopAnalysisInfo::kUnknownTripCount) {
- return false;
- }
-
- int64_t instruction_count = analysis_info->GetNumberOfInstructions();
- int64_t total_instruction_count = trip_count * instruction_count;
-
- // The inclusion of the HasInstructionsPreventingScalarOpts() prevents this
- // optimization from being applied to loops that have calls.
- bool can_optimize =
- total_instruction_count <= HLoopOptimization::kMaxTotalInstRemoveSuspendCheck &&
- !analysis_info->HasInstructionsPreventingScalarOpts();
-
- if (!can_optimize) {
- return false;
- }
-
- if (generate_code) {
- HLoopInformation* loop_info = analysis_info->GetLoopInfo();
- HBasicBlock* header = loop_info->GetHeader();
- HInstruction* instruction = header->GetLoopInformation()->GetSuspendCheck();
- header->RemoveInstruction(instruction);
- loop_info->SetSuspendCheck(nullptr);
- }
-
- return true;
-}
-
-//
// Optimization.
//
@@ -820,7 +779,7 @@
}
bool HLoopOptimization::OptimizeInnerLoop(LoopNode* node) {
- return TryOptimizeInnerLoopFinite(node) || TryLoopScalarOpts(node);
+ return TryOptimizeInnerLoopFinite(node) || TryPeelingAndUnrolling(node);
}
@@ -926,7 +885,7 @@
return true;
}
-bool HLoopOptimization::TryLoopScalarOpts(LoopNode* node) {
+bool HLoopOptimization::TryPeelingAndUnrolling(LoopNode* node) {
HLoopInformation* loop_info = node->loop_info;
int64_t trip_count = LoopAnalysis::GetLoopTripCount(loop_info, &induction_range_);
LoopAnalysisInfo analysis_info(loop_info);
@@ -939,16 +898,10 @@
if (!TryFullUnrolling(&analysis_info, /*generate_code*/ false) &&
!TryPeelingForLoopInvariantExitsElimination(&analysis_info, /*generate_code*/ false) &&
- !TryUnrollingForBranchPenaltyReduction(&analysis_info, /*generate_code*/ false) &&
- !TryToRemoveSuspendCheckFromLoopHeader(&analysis_info, /*generate_code*/ false)) {
+ !TryUnrollingForBranchPenaltyReduction(&analysis_info, /*generate_code*/ false)) {
return false;
}
- // Try the suspend check removal even for non-clonable loops. Also this
- // optimization doesn't interfere with other scalar loop optimizations so it can
- // be done prior to them.
- bool removed_suspend_check = TryToRemoveSuspendCheckFromLoopHeader(&analysis_info);
-
// Run 'IsLoopClonable' the last as it might be time-consuming.
if (!LoopClonerHelper::IsLoopClonable(loop_info)) {
return false;
@@ -956,7 +909,7 @@
return TryFullUnrolling(&analysis_info) ||
TryPeelingForLoopInvariantExitsElimination(&analysis_info) ||
- TryUnrollingForBranchPenaltyReduction(&analysis_info) || removed_suspend_check;
+ TryUnrollingForBranchPenaltyReduction(&analysis_info);
}
//
diff --git a/compiler/optimizing/loop_optimization.h b/compiler/optimizing/loop_optimization.h
index 0ca16b5..d3583ed 100644
--- a/compiler/optimizing/loop_optimization.h
+++ b/compiler/optimizing/loop_optimization.h
@@ -47,11 +47,6 @@
static constexpr const char* kLoopOptimizationPassName = "loop_optimization";
- // The maximum number of total instructions (trip_count * instruction_count),
- // where the optimization of removing SuspendChecks from the loop header could
- // be performed.
- static constexpr int64_t kMaxTotalInstRemoveSuspendCheck = 128;
-
private:
/**
* A single loop inside the loop hierarchy representation.
@@ -168,19 +163,8 @@
// should be actually applied.
bool TryFullUnrolling(LoopAnalysisInfo* analysis_info, bool generate_code = true);
- // Tries to remove SuspendCheck for plain loops with a low trip count. The
- // SuspendCheck in the codegen makes sure that the thread can be interrupted
- // during execution for GC. Not being able to do so might decrease the
- // responsiveness of GC when a very long loop or a long recursion is being
- // executed. However, for plain loops with a small trip count, the removal of
- // SuspendCheck should not affect the GC's responsiveness by a large margin.
- // Consequently, since the thread won't be interrupted for plain loops, it is
- // assumed that the performance might increase by removing SuspendCheck.
- bool TryToRemoveSuspendCheckFromLoopHeader(LoopAnalysisInfo* analysis_info,
- bool generate_code = true);
-
- // Tries to apply scalar loop optimizations.
- bool TryLoopScalarOpts(LoopNode* node);
+ // Tries to apply scalar loop peeling and unrolling.
+ bool TryPeelingAndUnrolling(LoopNode* node);
//
// Vectorization analysis and synthesis.
diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index 94eae4d..06fb88e 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -675,13 +675,6 @@
return cha_single_implementation_list_;
}
- // In case of OSR we intend to use SuspendChecks as an entry point to the
- // function; for debuggable graphs we might deoptimize to interpreter from
- // SuspendChecks. In these cases we shouldn't remove them.
- bool SuspendChecksAreAllowedToBeRemoved() const {
- return !IsDebuggable() && !IsCompilingOsr();
- }
-
void AddCHASingleImplementationDependency(ArtMethod* method) {
cha_single_implementation_list_.insert(method);
}