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8164954: split_if creates empty phi and region nodes

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Don't split if all edges will be moved to new phi

Reviewed-by: kvn, vlivanov
This commit is contained in:
Nils Eliasson 2017-03-06 14:08:52 +01:00
parent 344eafdf14
commit de10f56d52
1 changed files with 7 additions and 0 deletions
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7
hotspot/src/share/vm/opto/ifnode.cpp
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@ -249,6 +249,13 @@ static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
predicate_proj = proj; predicate_proj = proj;
} }
} }
// If all the defs of the phi are the same constant, we already have the desired end state.
// Skip the split that would create empty phi and region nodes.
if((r->req() - req_c) == 1) {
return NULL;
}
if (nb_predicate_proj > 1) { if (nb_predicate_proj > 1) {
// Can happen in case of loop unswitching and when the loop is // Can happen in case of loop unswitching and when the loop is
// optimized out: it's not a loop anymore so we don't care about // optimized out: it's not a loop anymore so we don't care about