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8375055: C2: Better dead loop detection printout

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Reviewed-by: chagedorn, qamai
This commit is contained in:
Aleksey Shipilev 2026-01-14 07:21:25 +00:00
parent 624d7144f7
commit 1b6c2bdd7b
1 changed files with 28 additions and 18 deletions
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46
src/hotspot/share/opto/phaseX.cpp
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@ -762,26 +762,36 @@ bool PhaseGVN::is_dominator_helper(Node *d, Node *n, bool linear_only) {
//------------------------------dead_loop_check--------------------------------
// Check for a simple dead loop when a data node references itself directly
// or through an other data node excluding cons and phis.
void PhaseGVN::dead_loop_check( Node *n ) {
// Phi may reference itself in a loop
if (n != nullptr && !n->is_dead_loop_safe() && !n->is_CFG()) {
// Do 2 levels check and only data inputs.
bool no_dead_loop = true;
uint cnt = n->req();
for (uint i = 1; i < cnt && no_dead_loop; i++) {
Node *in = n->in(i);
if (in == n) {
no_dead_loop = false;
} else if (in != nullptr && !in->is_dead_loop_safe()) {
uint icnt = in->req();
for (uint j = 1; j < icnt && no_dead_loop; j++) {
if (in->in(j) == n || in->in(j) == in)
no_dead_loop = false;
}
void PhaseGVN::dead_loop_check(Node* n) {
// Phi may reference itself in a loop.
if (n == nullptr || n->is_dead_loop_safe() || n->is_CFG()) {
return;
}
// Do 2 levels check and only data inputs.
for (uint i = 1; i < n->req(); i++) {
Node* in = n->in(i);
if (in == n) {
n->dump_bfs(100, nullptr, "");
fatal("Dead loop detected, node references itself: %s (%d)",
n->Name(), n->_idx);
}
if (in == nullptr || in->is_dead_loop_safe()) {
continue;
}
for (uint j = 1; j < in->req(); j++) {
if (in->in(j) == n) {
n->dump_bfs(100, nullptr, "");
fatal("Dead loop detected, node input references current node: %s (%d) -> %s (%d)",
in->Name(), in->_idx, n->Name(), n->_idx);
}
if (in->in(j) == in) {
n->dump_bfs(100, nullptr, "");
fatal("Dead loop detected, node input references itself: %s (%d)",
in->Name(), in->_idx);
}
}
if (!no_dead_loop) { n->dump_bfs(100, nullptr, ""); }
assert(no_dead_loop, "dead loop detected");
}
}