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8001345: VM crashes with assert(n->outcnt() != 0 || C->top() == n || n->is_Proj()) failed: No dead instructions after post-alloc

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Remove unnecessary LoadN / DecodeN nodes at MemBarAcquire nodes.

Reviewed-by: kvn, roland
This commit is contained in:
Niclas Adlertz 2013-06-19 00:41:56 +02:00
parent 7ddef5cd69
commit 556b4925b3
1 changed files with 11 additions and 1 deletions
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12
hotspot/src/share/vm/opto/memnode.cpp
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@ -2930,7 +2930,9 @@ MemBarNode* MemBarNode::make(Compile* C, int opcode, int atp, Node* pn) {
Node *MemBarNode::Ideal(PhaseGVN *phase, bool can_reshape) { Node *MemBarNode::Ideal(PhaseGVN *phase, bool can_reshape) {
if (remove_dead_region(phase, can_reshape)) return this; if (remove_dead_region(phase, can_reshape)) return this;
// Don't bother trying to transform a dead node // Don't bother trying to transform a dead node
if (in(0) && in(0)->is_top()) return NULL; if (in(0) && in(0)->is_top()) {
return NULL;
}
// Eliminate volatile MemBars for scalar replaced objects. // Eliminate volatile MemBars for scalar replaced objects.
if (can_reshape && req() == (Precedent+1)) { if (can_reshape && req() == (Precedent+1)) {
@ -2939,6 +2941,14 @@ Node *MemBarNode::Ideal(PhaseGVN *phase, bool can_reshape) {
if ((opc == Op_MemBarAcquire || opc == Op_MemBarVolatile)) { if ((opc == Op_MemBarAcquire || opc == Op_MemBarVolatile)) {
// Volatile field loads and stores. // Volatile field loads and stores.
Node* my_mem = in(MemBarNode::Precedent); Node* my_mem = in(MemBarNode::Precedent);
// The MembarAquire may keep an unused LoadNode alive through the Precedent edge
if ((my_mem != NULL) && (opc == Op_MemBarAcquire) && (my_mem->outcnt() == 1)) {
assert(my_mem->unique_out() == this, "sanity");
phase->hash_delete(this);
del_req(Precedent);
phase->is_IterGVN()->_worklist.push(my_mem); // remove dead node later
my_mem = NULL;
}
if (my_mem != NULL && my_mem->is_Mem()) { if (my_mem != NULL && my_mem->is_Mem()) {
const TypeOopPtr* t_oop = my_mem->in(MemNode::Address)->bottom_type()->isa_oopptr(); const TypeOopPtr* t_oop = my_mem->in(MemNode::Address)->bottom_type()->isa_oopptr();
// Check for scalar replaced object reference. // Check for scalar replaced object reference.