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7032963: StoreCM shouldn't participate in store elimination

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Reviewed-by: kvn
This commit is contained in:
Tom Rodriguez 2011-04-05 19:14:03 -07:00
parent 154f0709bd
commit aac4647e6e
4 changed files with 88 additions and 22 deletions
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58
hotspot/src/share/vm/opto/compile.cpp
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@ -2050,6 +2050,52 @@ static bool oop_offset_is_sane(const TypeInstPtr* tp) {
// Note that OffsetBot and OffsetTop are very negative.
}
// Eliminate trivially redundant StoreCMs and accumulate their
// precedence edges.
static void eliminate_redundant_card_marks(Node* n) {
assert(n->Opcode() == Op_StoreCM, "expected StoreCM");
if (n->in(MemNode::Address)->outcnt() > 1) {
// There are multiple users of the same address so it might be
// possible to eliminate some of the StoreCMs
Node* mem = n->in(MemNode::Memory);
Node* adr = n->in(MemNode::Address);
Node* val = n->in(MemNode::ValueIn);
Node* prev = n;
bool done = false;
// Walk the chain of StoreCMs eliminating ones that match. As
// long as it's a chain of single users then the optimization is
// safe. Eliminating partially redundant StoreCMs would require
// cloning copies down the other paths.
while (mem->Opcode() == Op_StoreCM && mem->outcnt() == 1 && !done) {
if (adr == mem->in(MemNode::Address) &&
val == mem->in(MemNode::ValueIn)) {
// redundant StoreCM
if (mem->req() > MemNode::OopStore) {
// Hasn't been processed by this code yet.
n->add_prec(mem->in(MemNode::OopStore));
} else {
// Already converted to precedence edge
for (uint i = mem->req(); i < mem->len(); i++) {
// Accumulate any precedence edges
if (mem->in(i) != NULL) {
n->add_prec(mem->in(i));
}
}
// Everything above this point has been processed.
done = true;
}
// Eliminate the previous StoreCM
prev->set_req(MemNode::Memory, mem->in(MemNode::Memory));
assert(mem->outcnt() == 0, "should be dead");
mem->disconnect_inputs(NULL);
} else {
prev = mem;
}
mem = prev->in(MemNode::Memory);
}
}
}
//------------------------------final_graph_reshaping_impl----------------------
// Implement items 1-5 from final_graph_reshaping below.
static void final_graph_reshaping_impl( Node *n, Final_Reshape_Counts &frc ) {
@ -2176,9 +2222,19 @@ static void final_graph_reshaping_impl( Node *n, Final_Reshape_Counts &frc ) {
frc.inc_float_count();
goto handle_mem;
case Op_StoreCM:
{
// Convert OopStore dependence into precedence edge
Node* prec = n->in(MemNode::OopStore);
n->del_req(MemNode::OopStore);
n->add_prec(prec);
eliminate_redundant_card_marks(n);
}
// fall through
case Op_StoreB:
case Op_StoreC:
case Op_StoreCM:
case Op_StorePConditional:
case Op_StoreI:
case Op_StoreL: