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6991577: add IfOp optimization to C1

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Ifop optimization for c1

Reviewed-by: never, phh, iveresov
This commit is contained in:
Roland Westrelin 2010-10-15 09:38:20 +02:00
parent 225a3b0eb8
commit e1a504b343
6 changed files with 246 additions and 173 deletions
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8
hotspot/src/share/vm/c1/c1_Compilation.hpp
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@ -178,15 +178,11 @@ class Compilation: public StackObj {
return (int) NMethodSizeLimit; // default 256K or 512K
#else
// conditional branches on PPC are restricted to 16 bit signed
return MAX2((unsigned int)NMethodSizeLimit,32*K);
return MIN2((unsigned int)NMethodSizeLimit,32*K);
#endif
}
static int desired_max_constant_size() {
#ifndef PPC
return (int) NMethodSizeLimit / 10; // about 25K
#else
return (MAX2((unsigned int)NMethodSizeLimit, 32*K)) / 10;
#endif
return desired_max_code_buffer_size() / 10;
}
static void setup_code_buffer(CodeBuffer* cb, int call_stub_estimate);

2
hotspot/src/share/vm/c1/c1_IR.cpp
View File

@ -321,7 +321,7 @@ class UseCountComputer: public ValueVisitor, BlockClosure {
void visit(Value* n) {
// Local instructions and Phis for expression stack values at the
// start of basic blocks are not added to the instruction list
if (!(*n)->is_linked()&& (*n)->can_be_linked()) {
if (!(*n)->is_linked() && (*n)->can_be_linked()) {
assert(false, "a node was not appended to the graph");
Compilation::current()->bailout("a node was not appended to the graph");
}

38
hotspot/src/share/vm/c1/c1_Instruction.cpp
View File

@ -415,28 +415,26 @@ bool Constant::is_equal(Value v) const {
return false;
}
BlockBegin* Constant::compare(Instruction::Condition cond, Value right,
BlockBegin* true_sux, BlockBegin* false_sux) {
Constant::CompareResult Constant::compare(Instruction::Condition cond, Value right) const {
Constant* rc = right->as_Constant();
// other is not a constant
if (rc == NULL) return NULL;
if (rc == NULL) return not_comparable;
ValueType* lt = type();
ValueType* rt = rc->type();
// different types
if (lt->base() != rt->base()) return NULL;
if (lt->base() != rt->base()) return not_comparable;
switch (lt->tag()) {
case intTag: {
int x = lt->as_IntConstant()->value();
int y = rt->as_IntConstant()->value();
switch (cond) {
case If::eql: return x == y ? true_sux : false_sux;
case If::neq: return x != y ? true_sux : false_sux;
case If::lss: return x < y ? true_sux : false_sux;
case If::leq: return x <= y ? true_sux : false_sux;
case If::gtr: return x > y ? true_sux : false_sux;
case If::geq: return x >= y ? true_sux : false_sux;
case If::eql: return x == y ? cond_true : cond_false;
case If::neq: return x != y ? cond_true : cond_false;
case If::lss: return x < y ? cond_true : cond_false;
case If::leq: return x <= y ? cond_true : cond_false;
case If::gtr: return x > y ? cond_true : cond_false;
case If::geq: return x >= y ? cond_true : cond_false;
}
break;
}
@ -444,12 +442,12 @@ BlockBegin* Constant::compare(Instruction::Condition cond, Value right,
jlong x = lt->as_LongConstant()->value();
jlong y = rt->as_LongConstant()->value();
switch (cond) {
case If::eql: return x == y ? true_sux : false_sux;
case If::neq: return x != y ? true_sux : false_sux;
case If::lss: return x < y ? true_sux : false_sux;
case If::leq: return x <= y ? true_sux : false_sux;
case If::gtr: return x > y ? true_sux : false_sux;
case If::geq: return x >= y ? true_sux : false_sux;
case If::eql: return x == y ? cond_true : cond_false;
case If::neq: return x != y ? cond_true : cond_false;
case If::lss: return x < y ? cond_true : cond_false;
case If::leq: return x <= y ? cond_true : cond_false;
case If::gtr: return x > y ? cond_true : cond_false;
case If::geq: return x >= y ? cond_true : cond_false;
}
break;
}
@ -459,14 +457,14 @@ BlockBegin* Constant::compare(Instruction::Condition cond, Value right,
assert(xvalue != NULL && yvalue != NULL, "not constants");
if (xvalue->is_loaded() && yvalue->is_loaded()) {
switch (cond) {
case If::eql: return xvalue == yvalue ? true_sux : false_sux;
case If::neq: return xvalue != yvalue ? true_sux : false_sux;
case If::eql: return xvalue == yvalue ? cond_true : cond_false;
case If::neq: return xvalue != yvalue ? cond_true : cond_false;
}
}
break;
}
}
return NULL;
return not_comparable;
}

22
hotspot/src/share/vm/c1/c1_Instruction.hpp
View File

@ -443,7 +443,7 @@ class Instruction: public CompilationResourceObj {
// generic
virtual Instruction* as_Instruction() { return this; } // to satisfy HASHING1 macro
virtual Phi* as_Phi() { return NULL; }
virtual Phi* as_Phi() { return NULL; }
virtual Local* as_Local() { return NULL; }
virtual Constant* as_Constant() { return NULL; }
virtual AccessField* as_AccessField() { return NULL; }
@ -650,8 +650,24 @@ LEAF(Constant, Instruction)
virtual intx hash() const;
virtual bool is_equal(Value v) const;
virtual BlockBegin* compare(Instruction::Condition condition, Value right,
BlockBegin* true_sux, BlockBegin* false_sux);
enum CompareResult { not_comparable = -1, cond_false, cond_true };
virtual CompareResult compare(Instruction::Condition condition, Value right) const;
BlockBegin* compare(Instruction::Condition cond, Value right,
BlockBegin* true_sux, BlockBegin* false_sux) const {
switch (compare(cond, right)) {
case not_comparable:
return NULL;
case cond_false:
return false_sux;
case cond_true:
return true_sux;
default:
ShouldNotReachHere();
return NULL;
}
}
};

346
hotspot/src/share/vm/c1/c1_Optimizer.cpp
View File

@ -38,18 +38,20 @@ class CE_Eliminator: public BlockClosure {
private:
IR* _hir;
int _cee_count; // the number of CEs successfully eliminated
int _ifop_count; // the number of IfOps successfully simplified
int _has_substitution;
public:
CE_Eliminator(IR* hir) : _cee_count(0), _hir(hir) {
CE_Eliminator(IR* hir) : _cee_count(0), _ifop_count(0), _hir(hir) {
_has_substitution = false;
_hir->iterate_preorder(this);
if (_has_substitution) {
// substituted some phis so resolve the substitution
// substituted some ifops/phis, so resolve the substitution
SubstitutionResolver sr(_hir);
}
}
int cee_count() const { return _cee_count; }
int ifop_count() const { return _ifop_count; }
void adjust_exception_edges(BlockBegin* block, BlockBegin* sux) {
int e = sux->number_of_exception_handlers();
@ -68,156 +70,214 @@ class CE_Eliminator: public BlockClosure {
}
}
virtual void block_do(BlockBegin* block) {
// 1) find conditional expression
// check if block ends with an If
If* if_ = block->end()->as_If();
if (if_ == NULL) return;
virtual void block_do(BlockBegin* block);
// check if If works on int or object types
// (we cannot handle If's working on long, float or doubles yet,
// since IfOp doesn't support them - these If's show up if cmp
// operations followed by If's are eliminated)
ValueType* if_type = if_->x()->type();
if (!if_type->is_int() && !if_type->is_object()) return;
BlockBegin* t_block = if_->tsux();
BlockBegin* f_block = if_->fsux();
Instruction* t_cur = t_block->next();
Instruction* f_cur = f_block->next();
// one Constant may be present between BlockBegin and BlockEnd
Value t_const = NULL;
Value f_const = NULL;
if (t_cur->as_Constant() != NULL && !t_cur->can_trap()) {
t_const = t_cur;
t_cur = t_cur->next();
}
if (f_cur->as_Constant() != NULL && !f_cur->can_trap()) {
f_const = f_cur;
f_cur = f_cur->next();
}
// check if both branches end with a goto
Goto* t_goto = t_cur->as_Goto();
if (t_goto == NULL) return;
Goto* f_goto = f_cur->as_Goto();
if (f_goto == NULL) return;
// check if both gotos merge into the same block
BlockBegin* sux = t_goto->default_sux();
if (sux != f_goto->default_sux()) return;
// check if at least one word was pushed on sux_state
ValueStack* sux_state = sux->state();
if (sux_state->stack_size() <= if_->state()->stack_size()) return;
// check if phi function is present at end of successor stack and that
// only this phi was pushed on the stack
Value sux_phi = sux_state->stack_at(if_->state()->stack_size());
if (sux_phi == NULL || sux_phi->as_Phi() == NULL || sux_phi->as_Phi()->block() != sux) return;
if (sux_phi->type()->size() != sux_state->stack_size() - if_->state()->stack_size()) return;
// get the values that were pushed in the true- and false-branch
Value t_value = t_goto->state()->stack_at(if_->state()->stack_size());
Value f_value = f_goto->state()->stack_at(if_->state()->stack_size());
// backend does not support floats
assert(t_value->type()->base() == f_value->type()->base(), "incompatible types");
if (t_value->type()->is_float_kind()) return;
// check that successor has no other phi functions but sux_phi
// this can happen when t_block or f_block contained additonal stores to local variables
// that are no longer represented by explicit instructions
for_each_phi_fun(sux, phi,
if (phi != sux_phi) return;
);
// true and false blocks can't have phis
for_each_phi_fun(t_block, phi, return; );
for_each_phi_fun(f_block, phi, return; );
// 2) substitute conditional expression
// with an IfOp followed by a Goto
// cut if_ away and get node before
Instruction* cur_end = if_->prev(block);
// append constants of true- and false-block if necessary
// clone constants because original block must not be destroyed
assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch");
if (t_value == t_const) {
t_value = new Constant(t_const->type());
NOT_PRODUCT(t_value->set_printable_bci(if_->printable_bci()));
cur_end = cur_end->set_next(t_value);
}
if (f_value == f_const) {
f_value = new Constant(f_const->type());
NOT_PRODUCT(f_value->set_printable_bci(if_->printable_bci()));
cur_end = cur_end->set_next(f_value);
}
// it is very unlikely that the condition can be statically decided
// (this was checked previously by the Canonicalizer), so always
// append IfOp
Value result = new IfOp(if_->x(), if_->cond(), if_->y(), t_value, f_value);
NOT_PRODUCT(result->set_printable_bci(if_->printable_bci()));
cur_end = cur_end->set_next(result);
// append Goto to successor
ValueStack* state_before = if_->is_safepoint() ? if_->state_before() : NULL;
Goto* goto_ = new Goto(sux, state_before, if_->is_safepoint() || t_goto->is_safepoint() || f_goto->is_safepoint());
// prepare state for Goto
ValueStack* goto_state = if_->state();
while (sux_state->scope() != goto_state->scope()) {
goto_state = goto_state->caller_state();
assert(goto_state != NULL, "states do not match up");
}
goto_state = goto_state->copy(ValueStack::StateAfter, goto_state->bci());
goto_state->push(result->type(), result);
assert(goto_state->is_same(sux_state), "states must match now");
goto_->set_state(goto_state);
cur_end = cur_end->set_next(goto_, goto_state->bci());
// Adjust control flow graph
BlockBegin::disconnect_edge(block, t_block);
BlockBegin::disconnect_edge(block, f_block);
if (t_block->number_of_preds() == 0) {
BlockBegin::disconnect_edge(t_block, sux);
}
adjust_exception_edges(block, t_block);
if (f_block->number_of_preds() == 0) {
BlockBegin::disconnect_edge(f_block, sux);
}
adjust_exception_edges(block, f_block);
// update block end
block->set_end(goto_);
// substitute the phi if possible
if (sux_phi->as_Phi()->operand_count() == 1) {
assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi");
sux_phi->set_subst(result);
_has_substitution = true;
}
// 3) successfully eliminated a conditional expression
_cee_count++;
if (PrintCEE) {
tty->print_cr("%d. CEE in B%d (B%d B%d)", cee_count(), block->block_id(), t_block->block_id(), f_block->block_id());
}
_hir->verify();
}
private:
Value make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval);
};
void CE_Eliminator::block_do(BlockBegin* block) {
// 1) find conditional expression
// check if block ends with an If
If* if_ = block->end()->as_If();
if (if_ == NULL) return;
// check if If works on int or object types
// (we cannot handle If's working on long, float or doubles yet,
// since IfOp doesn't support them - these If's show up if cmp
// operations followed by If's are eliminated)
ValueType* if_type = if_->x()->type();
if (!if_type->is_int() && !if_type->is_object()) return;
BlockBegin* t_block = if_->tsux();
BlockBegin* f_block = if_->fsux();
Instruction* t_cur = t_block->next();
Instruction* f_cur = f_block->next();
// one Constant may be present between BlockBegin and BlockEnd
Value t_const = NULL;
Value f_const = NULL;
if (t_cur->as_Constant() != NULL && !t_cur->can_trap()) {
t_const = t_cur;
t_cur = t_cur->next();
}
if (f_cur->as_Constant() != NULL && !f_cur->can_trap()) {
f_const = f_cur;
f_cur = f_cur->next();
}
// check if both branches end with a goto
Goto* t_goto = t_cur->as_Goto();
if (t_goto == NULL) return;
Goto* f_goto = f_cur->as_Goto();
if (f_goto == NULL) return;
// check if both gotos merge into the same block
BlockBegin* sux = t_goto->default_sux();
if (sux != f_goto->default_sux()) return;
// check if at least one word was pushed on sux_state
ValueStack* sux_state = sux->state();
if (sux_state->stack_size() <= if_->state()->stack_size()) return;
// check if phi function is present at end of successor stack and that
// only this phi was pushed on the stack
Value sux_phi = sux_state->stack_at(if_->state()->stack_size());
if (sux_phi == NULL || sux_phi->as_Phi() == NULL || sux_phi->as_Phi()->block() != sux) return;
if (sux_phi->type()->size() != sux_state->stack_size() - if_->state()->stack_size()) return;
// get the values that were pushed in the true- and false-branch
Value t_value = t_goto->state()->stack_at(if_->state()->stack_size());
Value f_value = f_goto->state()->stack_at(if_->state()->stack_size());
// backend does not support floats
assert(t_value->type()->base() == f_value->type()->base(), "incompatible types");
if (t_value->type()->is_float_kind()) return;
// check that successor has no other phi functions but sux_phi
// this can happen when t_block or f_block contained additonal stores to local variables
// that are no longer represented by explicit instructions
for_each_phi_fun(sux, phi,
if (phi != sux_phi) return;
);
// true and false blocks can't have phis
for_each_phi_fun(t_block, phi, return; );
for_each_phi_fun(f_block, phi, return; );
// 2) substitute conditional expression
// with an IfOp followed by a Goto
// cut if_ away and get node before
Instruction* cur_end = if_->prev(block);
// append constants of true- and false-block if necessary
// clone constants because original block must not be destroyed
assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch");
if (t_value == t_const) {
t_value = new Constant(t_const->type());
NOT_PRODUCT(t_value->set_printable_bci(if_->printable_bci()));
cur_end = cur_end->set_next(t_value);
}
if (f_value == f_const) {
f_value = new Constant(f_const->type());
NOT_PRODUCT(f_value->set_printable_bci(if_->printable_bci()));
cur_end = cur_end->set_next(f_value);
}
Value result = make_ifop(if_->x(), if_->cond(), if_->y(), t_value, f_value);
assert(result != NULL, "make_ifop must return a non-null instruction");
if (!result->is_linked() && result->can_be_linked()) {
NOT_PRODUCT(result->set_printable_bci(if_->printable_bci()));
cur_end = cur_end->set_next(result);
}
// append Goto to successor
ValueStack* state_before = if_->is_safepoint() ? if_->state_before() : NULL;
Goto* goto_ = new Goto(sux, state_before, if_->is_safepoint() || t_goto->is_safepoint() || f_goto->is_safepoint());
// prepare state for Goto
ValueStack* goto_state = if_->state();
while (sux_state->scope() != goto_state->scope()) {
goto_state = goto_state->caller_state();
assert(goto_state != NULL, "states do not match up");
}
goto_state = goto_state->copy(ValueStack::StateAfter, goto_state->bci());
goto_state->push(result->type(), result);
assert(goto_state->is_same(sux_state), "states must match now");
goto_->set_state(goto_state);
cur_end = cur_end->set_next(goto_, goto_state->bci());
// Adjust control flow graph
BlockBegin::disconnect_edge(block, t_block);
BlockBegin::disconnect_edge(block, f_block);
if (t_block->number_of_preds() == 0) {
BlockBegin::disconnect_edge(t_block, sux);
}
adjust_exception_edges(block, t_block);
if (f_block->number_of_preds() == 0) {
BlockBegin::disconnect_edge(f_block, sux);
}
adjust_exception_edges(block, f_block);
// update block end
block->set_end(goto_);
// substitute the phi if possible
if (sux_phi->as_Phi()->operand_count() == 1) {
assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi");
sux_phi->set_subst(result);
_has_substitution = true;
}
// 3) successfully eliminated a conditional expression
_cee_count++;
if (PrintCEE) {
tty->print_cr("%d. CEE in B%d (B%d B%d)", cee_count(), block->block_id(), t_block->block_id(), f_block->block_id());
tty->print_cr("%d. IfOp in B%d", ifop_count(), block->block_id());
}
_hir->verify();
}
Value CE_Eliminator::make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval) {
if (!OptimizeIfOps) {
return new IfOp(x, cond, y, tval, fval);
}
tval = tval->subst();
fval = fval->subst();
if (tval == fval) {
_ifop_count++;
return tval;
}
x = x->subst();
y = y->subst();
Constant* y_const = y->as_Constant();
if (y_const != NULL) {
IfOp* x_ifop = x->as_IfOp();
if (x_ifop != NULL) { // x is an ifop, y is a constant
Constant* x_tval_const = x_ifop->tval()->subst()->as_Constant();
Constant* x_fval_const = x_ifop->fval()->subst()->as_Constant();
if (x_tval_const != NULL && x_fval_const != NULL) {
Instruction::Condition x_ifop_cond = x_ifop->cond();
Constant::CompareResult t_compare_res = x_tval_const->compare(cond, y_const);
Constant::CompareResult f_compare_res = x_fval_const->compare(cond, y_const);
guarantee(t_compare_res != Constant::not_comparable && f_compare_res != Constant::not_comparable, "incomparable constants in IfOp");
Value new_tval = t_compare_res == Constant::cond_true ? tval : fval;
Value new_fval = f_compare_res == Constant::cond_true ? tval : fval;
_ifop_count++;
if (new_tval == new_fval) {
return new_tval;
} else {
return new IfOp(x_ifop->x(), x_ifop_cond, x_ifop->y(), new_tval, new_fval);
}
}
} else {
Constant* x_const = x->as_Constant();
if (x_const != NULL) { // x and y are constants
Constant::CompareResult x_compare_res = x_const->compare(cond, y_const);
guarantee(x_compare_res != Constant::not_comparable, "incomparable constants in IfOp");
_ifop_count++;
return x_compare_res == Constant::cond_true ? tval : fval;
}
}
}
return new IfOp(x, cond, y, tval, fval);
}
void Optimizer::eliminate_conditional_expressions() {
// find conditional expressions & replace them with IfOps
CE_Eliminator ce(ir());
}
class BlockMerger: public BlockClosure {
private:
IR* _hir;

3
hotspot/src/share/vm/c1/c1_globals.hpp
View File

@ -75,6 +75,9 @@
develop(bool, SelectivePhiFunctions, true, \
"create phi functions at loop headers only when necessary") \
\
develop(bool, OptimizeIfOps, true, \
"Optimize multiple IfOps") \
\
develop(bool, DoCEE, true, \
"Do Conditional Expression Elimination to simplify CFG") \
\