// ------------------------------------------------------------------
// ciFieldLayout::ciFieldLayout
ciFieldLayout::ciFieldLayout(ciInstanceKlass* my_klass) {
assert(my_klass->is_loaded(), "must be loaded");
ASSERT_IN_VM;
klassOop klass = my_klass->get_klassOop();
Arena* arena = CURRENT_ENV->arena();
GrowableArray<BasicType>* fieldtypes =
new (arena) GrowableArray<BasicType>(arena, 8, 0, T_VOID);
GrowableArray<int>* aflags =
new (arena) GrowableArray<int>(arena, 8, 0, 0);
GrowableArray<int>* fieldoffsets =
new (arena) GrowableArray<int>(arena, 8, 0, 0);
int pos = 0;
fill_in_header_fields(fieldtypes, fieldoffsets, pos);
_header_count = pos;
fill_in_instance_fields(fieldtypes, fieldoffsets, aflags, pos, klass);
#if 0
// [RGV] instance size is in word's but pos is number
// of fields.
int fill_to = my_klass->instance_size();
if (fieldtypes->length() < fill_to)
fields->at_put_grow(fill_to-1, T_VOID, T_VOID);
if (aflags->length() < fill_to)
aflags->at_put_grow(fill_to-1, 0, 0);
#endif
_fieldtypes = fieldtypes;
_access_flags = aflags;
_fieldoffsets = fieldoffsets;
}
//------------------------------implicit_null_check----------------------------
// Detect implicit-null-check opportunities. Basically, find NULL checks
// with suitable memory ops nearby. Use the memory op to do the NULL check.
// I can generate a memory op if there is not one nearby.
void Block::implicit_null_check(Block_Array &bbs, GrowableArray<uint> &latency, Node *proj, Node *val) {
// Assume if null check need for 0 offset then always needed
// Intel solaris doesn't support any null checks yet and no
// mechanism exists (yet) to set the switches at an os_cpu level
if( !ImplicitNullChecks || MacroAssembler::needs_explicit_null_check(0)) return;
// Make sure the ptr-is-null path appears to be uncommon!
float f = end()->is_Mach()->is_MachIf()->_prob;
if( proj->Opcode() == Op_IfTrue ) f = 1.0f - f;
if( f > 0.0001 ) return;
uint bidx = 0; // Capture index of value into memop
bool was_store; // Memory op is a store op
// Search the successor block for a load or store who's base value is also
// the tested value. There may be several.
Node_List *out = new Node_List(Thread::current()->resource_area());
MachNode *best = NULL; // Best found so far
for (DUIterator i = val->outs(); val->has_out(i); i++) {
MachNode *mach = val->out(i)->is_Mach();
if( !mach ) continue;
was_store = false;
switch( mach->ideal_Opcode() ) {
case Op_LoadB:
case Op_LoadC:
case Op_LoadD:
case Op_LoadF:
case Op_LoadI:
case Op_LoadL:
case Op_LoadP:
case Op_LoadS:
case Op_LoadKlass:
case Op_LoadRange:
case Op_LoadD_unaligned:
case Op_LoadL_unaligned:
break;
case Op_StoreB:
case Op_StoreC:
case Op_StoreCM:
case Op_StoreD:
case Op_StoreF:
case Op_StoreI:
case Op_StoreL:
case Op_StoreP:
was_store = true; // Memory op is a store op
// Stores will have their address in slot 2 (memory in slot 1).
// If the value being nul-checked is in another slot, it means we
// are storing the checked value, which does NOT check the value!
if( mach->in(2) != val ) continue;
break; // Found a memory op?
case Op_StrComp:
// Not a legit memory op for implicit null check regardless of
// embedded loads
continue;
default: // Also check for embedded loads
if( !mach->check_for_anti_dependence() )
continue; // Not an memory op; skip it
break;
}
// check if the offset is not too high for implicit exception
{
intptr_t offset = 0;
const TypePtr *adr_type = NULL; // Do not need this return value here
const Node* base = mach->get_base_and_disp(offset, adr_type);
if (base == NULL || base == (Node*)-1) {
// cannot reason about it; is probably not implicit null exception
} else {
const TypePtr* tptr = base->bottom_type()->is_ptr();
// Give up if offset is not a compile-time constant
if( offset == Type::OffsetBot || tptr->_offset == Type::OffsetBot )
continue;
offset += tptr->_offset; // correct if base is offseted
if( MacroAssembler::needs_explicit_null_check(offset) )
continue; // Give up is reference is beyond 4K page size
}
}
// Check ctrl input to see if the null-check dominates the memory op
Block *cb = bbs[mach->_idx];
cb = cb->_idom; // Always hoist at least 1 block
if( !was_store ) { // Stores can be hoisted only one block
while( cb->_dom_depth > _dom_depth )
cb = cb->_idom; // Hoist loads as far as we want
}
if( cb != this ) continue;
// Found a memory user; see if it can be hoisted to check-block
uint vidx = 0; // Capture index of value into memop
uint j;
for( j = mach->req()-1; j > 0; j-- ) {
if( mach->in(j) == val ) vidx = j;
// Block of memory-op input
Block *inb = bbs[mach->in(j)->_idx];
Block *b = this; // Start from nul check
while( b != inb && b->_dom_depth > inb->_dom_depth )
b = b->_idom; // search upwards for input
// See if input dominates null check
if( b != inb )
break;
}
if( j > 0 )
continue;
Block *mb = bbs[mach->_idx];
// Hoisting stores requires more checks for the anti-dependence case.
// Give up hoisting if we have to move the store past any load.
if( was_store ) {
Block *b = mb; // Start searching here for a local load
// mach use (faulting) trying to hoist
// n might be blocker to hoisting
while( b != this ) {
uint k;
for( k = 1; k < b->_nodes.size(); k++ ) {
Node *n = b->_nodes[k];
if( n->check_for_anti_dependence() &&
n->in(LoadNode::Memory) == mach->in(StoreNode::Memory) )
break; // Found anti-dependent load
}
if( k < b->_nodes.size() )
break; // Found anti-dependent load
// Make sure control does not do a merge (would have to check allpaths)
if( b->num_preds() != 2 ) break;
b = bbs[b->pred(1)->_idx]; // Move up to predecessor block
}
if( b != this ) continue;
}
// Make sure this memory op is not already being used for a NullCheck
MachNode *e = mb->end()->is_Mach();
if( e && e->is_MachNullCheck() && e->in(1) == mach )
continue; // Already being used as a NULL check
// Found a candidate! Pick one with least dom depth - the highest
// in the dom tree should be closest to the null check.
if( !best ||
bbs[mach->_idx]->_dom_depth < bbs[best->_idx]->_dom_depth ) {
best = mach;
bidx = vidx;
}
}
// No candidate!
if( !best ) return;
// ---- Found an implicit null check
extern int implicit_null_checks;
implicit_null_checks++;
// Hoist the memory candidate up to the end of the test block.
Block *old_block = bbs[best->_idx];
old_block->find_remove(best);
add_inst(best);
bbs.map(best->_idx,this);
// Move the control dependence
if (best->in(0) && best->in(0) == old_block->_nodes[0])
best->set_req(0, _nodes[0]);
// Check for flag-killing projections that also need to be hoisted
// Should be DU safe because no edge updates.
for (DUIterator_Fast jmax, j = best->fast_outs(jmax); j < jmax; j++) {
Node* n = best->fast_out(j);
if( n->Opcode() == Op_MachProj ) {
bbs[n->_idx]->find_remove(n);
add_inst(n);
bbs.map(n->_idx,this);
}
}
// proj==Op_True --> ne test; proj==Op_False --> eq test.
// One of two graph shapes got matched:
// (IfTrue (If (Bool NE (CmpP ptr NULL))))
// (IfFalse (If (Bool EQ (CmpP ptr NULL))))
// NULL checks are always branch-if-eq. If we see a IfTrue projection
// then we are replacing a 'ne' test with a 'eq' NULL check test.
// We need to flip the projections to keep the same semantics.
if( proj->Opcode() == Op_IfTrue ) {
// Swap order of projections in basic block to swap branch targets
Node *tmp1 = _nodes[end_idx()+1];
Node *tmp2 = _nodes[end_idx()+2];
_nodes.map(end_idx()+1, tmp2);
_nodes.map(end_idx()+2, tmp1);
Node *tmp = new (1) Node(1);
tmp1->replace_by(tmp);
tmp2->replace_by(tmp1);
tmp->replace_by(tmp2);
}
// Remove the existing null check; use a new implicit null check instead.
// Since schedule-local needs precise def-use info, we need to correct
// it as well.
Node *old_tst = proj->in(0);
MachNode *nul_chk = new MachNullCheckNode(old_tst->in(0),best,bidx);
_nodes.map(end_idx(),nul_chk);
bbs.map(nul_chk->_idx,this);
// Redirect users of old_test to nul_chk
for (DUIterator_Last i2min, i2 = old_tst->last_outs(i2min); i2 >= i2min; --i2)
old_tst->last_out(i2)->set_req(0, nul_chk);
// Clean-up any dead code
for (uint i3 = 0; i3 < old_tst->req(); i3++)
old_tst->set_req(i3, NULL);
latency.at_put_grow(nul_chk->_idx, nul_chk->latency_from_uses(bbs, latency));
latency.at_put_grow(best ->_idx, best ->latency_from_uses(bbs, latency));
#ifndef PRODUCT
if (TraceOptoPipelining) {
tty->print("# implicit_null_check: latency %4d for ", latency.at_grow(best->_idx));
best->fast_dump();
tty->print("# implicit_null_check: latency %4d for ", latency.at_grow(nul_chk->_idx));
nul_chk->fast_dump();
}
#endif
}
