src/share/vm/c1/c1_ValueMap.cpp
Print this page
rev 4136 : 7153771: array bound check elimination for c1
Summary: when possible optimize out array bound checks, inserting predicates when needed.
Reviewed-by:
@@ -24,13 +24,13 @@
#include "precompiled.hpp"
#include "c1/c1_Canonicalizer.hpp"
#include "c1/c1_IR.hpp"
#include "c1/c1_ValueMap.hpp"
+#include "c1/c1_ValueStack.hpp"
#include "utilities/bitMap.inline.hpp"
-
#ifndef PRODUCT
int ValueMap::_number_of_finds = 0;
int ValueMap::_number_of_hits = 0;
int ValueMap::_number_of_kills = 0;
@@ -190,14 +190,10 @@
LoadField* lf = value->as_LoadField(); \
bool must_kill = lf != NULL \
&& lf->field()->holder() == field->holder() \
&& (all_offsets || lf->field()->offset() == field->offset());
-#define MUST_KILL_EXCEPTION(must_kill, entry, value) \
- assert(entry->nesting() < nesting(), "must not find bigger nesting than current"); \
- bool must_kill = (entry->nesting() == nesting() - 1);
-
void ValueMap::kill_memory() {
GENERIC_KILL_VALUE(MUST_KILL_MEMORY);
}
@@ -207,15 +203,10 @@
void ValueMap::kill_field(ciField* field, bool all_offsets) {
GENERIC_KILL_VALUE(MUST_KILL_FIELD);
}
-void ValueMap::kill_exception() {
- GENERIC_KILL_VALUE(MUST_KILL_EXCEPTION);
-}
-
-
void ValueMap::kill_map(ValueMap* map) {
assert(is_global_value_numbering(), "only for global value numbering");
_killed_values.set_union(&map->_killed_values);
}
@@ -272,31 +263,183 @@
class ShortLoopOptimizer : public ValueNumberingVisitor {
private:
GlobalValueNumbering* _gvn;
BlockList _loop_blocks;
bool _too_complicated_loop;
+ bool _has_field_store[T_ARRAY + 1];
+ bool _has_indexed_store[T_ARRAY + 1];
// simplified access to methods of GlobalValueNumbering
ValueMap* current_map() { return _gvn->current_map(); }
ValueMap* value_map_of(BlockBegin* block) { return _gvn->value_map_of(block); }
// implementation for abstract methods of ValueNumberingVisitor
void kill_memory() { _too_complicated_loop = true; }
- void kill_field(ciField* field, bool all_offsets) { current_map()->kill_field(field, all_offsets); };
- void kill_array(ValueType* type) { current_map()->kill_array(type); };
+ void kill_field(ciField* field, bool all_offsets) {
+ current_map()->kill_field(field, all_offsets);
+ assert(field->type()->basic_type() >= 0 && field->type()->basic_type() <= T_ARRAY, "Invalid type");
+ _has_field_store[field->type()->basic_type()] = true;
+ }
+ void kill_array(ValueType* type) {
+ current_map()->kill_array(type);
+ BasicType basic_type = as_BasicType(type); assert(basic_type >= 0 && basic_type <= T_ARRAY, "Invalid type");
+ _has_indexed_store[basic_type] = true;
+ }
public:
ShortLoopOptimizer(GlobalValueNumbering* gvn)
: _gvn(gvn)
, _loop_blocks(ValueMapMaxLoopSize)
, _too_complicated_loop(false)
{
+ for (int i=0; i<= T_ARRAY; i++){
+ _has_field_store[i] = false;
+ _has_indexed_store[i] = false;
+ }
+ }
+
+ bool has_field_store(BasicType type) {
+ assert(type >= 0 && type <= T_ARRAY, "Invalid type");
+ return _has_field_store[type];
+ }
+
+ bool has_indexed_store(BasicType type) {
+ assert(type >= 0 && type <= T_ARRAY, "Invalid type");
+ return _has_indexed_store[type];
}
bool process(BlockBegin* loop_header);
};
+class LoopInvariantCodeMotion : public StackObj {
+ private:
+ GlobalValueNumbering* _gvn;
+ ShortLoopOptimizer* _short_loop_optimizer;
+ Instruction* _insertion_point;
+ ValueStack * _state;
+
+ void set_invariant(Value v) const { _gvn->set_processed(v); }
+ bool is_invariant(Value v) const { return _gvn->is_processed(v); }
+
+ void process_block(BlockBegin* block);
+
+ public:
+ LoopInvariantCodeMotion(ShortLoopOptimizer *slo, GlobalValueNumbering* gvn, BlockBegin* loop_header, BlockList* loop_blocks);
+};
+
+LoopInvariantCodeMotion::LoopInvariantCodeMotion(ShortLoopOptimizer *slo, GlobalValueNumbering* gvn, BlockBegin* loop_header, BlockList* loop_blocks)
+ : _gvn(gvn), _short_loop_optimizer(slo)
+{
+
+ TRACE_VALUE_NUMBERING(tty->print_cr("using loop invariant code motion loop_header = %d", loop_header->block_id()));
+ TRACE_VALUE_NUMBERING(tty->print_cr("** loop invariant code motion for short loop B%d", loop_header->block_id()));
+
+ BlockBegin* insertion_block = loop_header->dominator();
+ if (insertion_block->number_of_preds() == 0) {
+ return; // only the entry block does not have a predecessor
+ }
+
+ assert(insertion_block->end()->as_Base() == NULL, "cannot insert into entry block");
+ _insertion_point = insertion_block->end()->prev();
+
+ BlockEnd *block_end = insertion_block->end();
+ _state = block_end->state_before();
+
+ if (!_state) {
+ // If, TableSwitch and LookupSwitch always have state_before when
+ // loop invariant code motion happens..
+ assert(block_end->as_Goto(), "Block has to be goto");
+ _state = block_end->state();
+ }
+
+ // the loop_blocks are filled by going backward from the loop header, so this processing order is best
+ assert(loop_blocks->at(0) == loop_header, "loop header must be first loop block");
+ process_block(loop_header);
+ for (int i = loop_blocks->length() - 1; i >= 1; i--) {
+ process_block(loop_blocks->at(i));
+ }
+}
+
+void LoopInvariantCodeMotion::process_block(BlockBegin* block) {
+
+ TRACE_VALUE_NUMBERING(tty->print_cr("processing block B%d", block->block_id()));
+
+ Instruction* prev = block;
+ Instruction* cur = block->next();
+
+ while (cur != NULL) {
+
+ // determine if cur instruction is loop invariant
+ // only selected instruction types are processed here
+ bool cur_invariant = false;
+
+ if (cur->as_Constant() != NULL) {
+
+ cur_invariant = !cur->can_trap();
+
+ } else if (cur->as_ArithmeticOp() != NULL || cur->as_LogicOp() != NULL || cur->as_ShiftOp() != NULL) {
+
+ assert(cur->as_Op2() != NULL, "must be Op2");
+ Op2* op2 = (Op2*)cur;
+ cur_invariant = !op2->can_trap() && is_invariant(op2->x()) && is_invariant(op2->y());
+
+ } else if (cur->as_LoadField() != NULL) {
+
+ LoadField* lf = (LoadField*)cur;
+
+ // deoptimizes on NullPointerException
+ cur_invariant = !lf->needs_patching() && !lf->field()->is_volatile() && !_short_loop_optimizer->has_field_store(lf->field()->type()->basic_type()) && is_invariant(lf->obj());
+ } else if (cur->as_ArrayLength() != NULL) {
+
+ ArrayLength *length = cur->as_ArrayLength();
+ cur_invariant = is_invariant(length->array());
+ } else if (cur->as_LoadIndexed() != NULL) {
+
+ LoadIndexed *li = (LoadIndexed *)cur->as_LoadIndexed();
+ cur_invariant = (!_short_loop_optimizer->has_indexed_store(li->elt_type())) && (is_invariant(li->array()) && is_invariant(li->index()));
+ }
+
+ if (cur_invariant) {
+
+ // perform value numbering and mark instruction as loop-invariant
+ _gvn->substitute(cur);
+
+ if (cur->as_Constant() == NULL) {
+ // ensure that code for non-constant instructions is always generated
+ cur->pin();
+ }
+
+ // remove cur instruction from loop block and append it to block before loop
+ Instruction* next = cur->next();
+
+ Instruction* in = _insertion_point->next();
+ _insertion_point = _insertion_point->set_next(cur);
+ cur->set_next(in);
+
+ // Deoptimize on exception
+ cur->set_flag(Instruction::DeoptimizeOnException, true);
+
+ // Clear exception handlers
+ cur->set_exception_handlers(NULL);
+
+ TRACE_VALUE_NUMBERING(tty->print_cr("Instruction %c%d is loop invariant", cur->type()->tchar(), cur->id()));
+
+ if (cur->state_before() != NULL) {
+ cur->set_state_before(_state->copy());
+ }
+ if (cur->exception_state() != NULL) {
+ cur->set_exception_state(_state->copy());
+ }
+
+ cur = prev->set_next(next);
+
+ } else {
+ prev = cur;
+ cur = cur->next();
+ }
+ }
+}
bool ShortLoopOptimizer::process(BlockBegin* loop_header) {
TRACE_VALUE_NUMBERING(tty->print_cr("** loop header block"));
_too_complicated_loop = false;
@@ -314,10 +457,14 @@
// add predecessors to worklist
for (int j = block->number_of_preds() - 1; j >= 0; j--) {
BlockBegin* pred = block->pred_at(j);
+ if (pred->is_set(BlockBegin::osr_entry_flag)) {
+ return false;
+ }
+
ValueMap* pred_map = value_map_of(pred);
if (pred_map != NULL) {
current_map()->kill_map(pred_map);
} else if (!_loop_blocks.contains(pred)) {
if (_loop_blocks.length() >= ValueMapMaxLoopSize) {
@@ -334,31 +481,43 @@
return false;
}
}
}
+ bool optimistic = this->_gvn->compilation()->is_optimistic();
+
+ if (UseLoopInvariantCodeMotion && optimistic) {
+ LoopInvariantCodeMotion code_motion(this, _gvn, loop_header, &_loop_blocks);
+ }
+
TRACE_VALUE_NUMBERING(tty->print_cr("** loop successfully optimized"));
return true;
}
GlobalValueNumbering::GlobalValueNumbering(IR* ir)
: _current_map(NULL)
, _value_maps(ir->linear_scan_order()->length(), NULL)
+ , _compilation(ir->compilation())
{
TRACE_VALUE_NUMBERING(tty->print_cr("****** start of global value numbering"));
ShortLoopOptimizer short_loop_optimizer(this);
- int subst_count = 0;
BlockList* blocks = ir->linear_scan_order();
int num_blocks = blocks->length();
BlockBegin* start_block = blocks->at(0);
assert(start_block == ir->start() && start_block->number_of_preds() == 0 && start_block->dominator() == NULL, "must be start block");
assert(start_block->next()->as_Base() != NULL && start_block->next()->next() == NULL, "start block must not have instructions");
+ // method parameters are not linked in instructions list, so process them separateley
+ for_each_state_value(start_block->state(), value,
+ assert(value->as_Local() != NULL, "only method parameters allowed");
+ set_processed(value);
+ );
+
// initial, empty value map with nesting 0
set_value_map_of(start_block, new ValueMap());
for (int i = 1; i < num_blocks; i++) {
BlockBegin* block = blocks->at(i);
@@ -372,11 +531,11 @@
assert(value_map_of(dominator) != NULL, "value map of dominator must exist");
// create new value map with increased nesting
_current_map = new ValueMap(value_map_of(dominator));
- if (num_preds == 1) {
+ if (num_preds == 1 && !block->is_set(BlockBegin::exception_entry_flag)) {
assert(dominator == block->pred_at(0), "dominator must be equal to predecessor");
// nothing to do here
} else if (block->is_set(BlockBegin::linear_scan_loop_header_flag)) {
// block has incoming backward branches -> try to optimize short loops
@@ -401,38 +560,43 @@
current_map()->kill_memory();
}
}
}
- if (block->is_set(BlockBegin::exception_entry_flag)) {
- current_map()->kill_exception();
- }
+ // phi functions are not linked in instructions list, so process them separateley
+ for_each_phi_fun(block, phi,
+ set_processed(phi);
+ );
TRACE_VALUE_NUMBERING(tty->print("value map before processing block: "); current_map()->print());
// visit all instructions of this block
for (Value instr = block->next(); instr != NULL; instr = instr->next()) {
- assert(!instr->has_subst(), "substitution already set");
-
// check if instruction kills any values
instr->visit(this);
-
- if (instr->hash() != 0) {
- Value f = current_map()->find_insert(instr);
- if (f != instr) {
- assert(!f->has_subst(), "can't have a substitution");
- instr->set_subst(f);
- subst_count++;
- }
- }
+ // perform actual value numbering
+ substitute(instr);
}
// remember value map for successors
set_value_map_of(block, current_map());
}
- if (subst_count != 0) {
+ if (_has_substitutions) {
SubstitutionResolver resolver(ir);
}
TRACE_VALUE_NUMBERING(tty->print("****** end of global value numbering. "); ValueMap::print_statistics());
}
+
+void GlobalValueNumbering::substitute(Instruction* instr) {
+ assert(!instr->has_subst(), "substitution already set");
+ Value subst = current_map()->find_insert(instr);
+ if (subst != instr) {
+ assert(!subst->has_subst(), "can't have a substitution");
+
+ TRACE_VALUE_NUMBERING(tty->print_cr("substitution for %d set to %d", instr->id(), subst->id()));
+ instr->set_subst(subst);
+ _has_substitutions = true;
+ }
+ set_processed(instr);
+}