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8330158: C2: Loop strip mining uses ABS with min int

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Reviewed-by: shade, kvn, dlong, mbalao
This commit is contained in:
Roland Westrelin 2024-04-29 07:36:14 +00:00
parent fb63cbadb4
commit c615c18e9f
1 changed files with 14 additions and 5 deletions
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19
src/hotspot/share/opto/loopnode.cpp
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@ -2352,7 +2352,8 @@ Node* PhaseIdealLoop::exact_limit( IdealLoopTree *loop ) {
CountedLoopNode *cl = loop->_head->as_CountedLoop();
assert(cl->is_valid_counted_loop(T_INT), "");
if (ABS(cl->stride_con()) == 1 ||
if (cl->stride_con() == 1 ||
cl->stride_con() == -1 ||
cl->limit()->Opcode() == Op_LoopLimit) {
// Old code has exact limit (it could be incorrect in case of int overflow).
// Loop limit is exact with stride == 1. And loop may already have exact limit.
@ -2962,14 +2963,22 @@ void OuterStripMinedLoopNode::adjust_strip_mined_loop(PhaseIterGVN* igvn) {
CountedLoopEndNode* inner_cle = inner_cl->loopexit();
int stride = inner_cl->stride_con();
jlong scaled_iters_long = ((jlong)LoopStripMiningIter) * ABS(stride);
// For a min int stride, LoopStripMiningIter * stride overflows the int range for all values of LoopStripMiningIter
// except 0 or 1. Those values are handled early on in this method and causes the method to return. So for a min int
// stride, the method is guaranteed to return at the next check below.
jlong scaled_iters_long = ((jlong)LoopStripMiningIter) * ABS((jlong)stride);
int scaled_iters = (int)scaled_iters_long;
int short_scaled_iters = LoopStripMiningIterShortLoop* ABS(stride);
if ((jlong)scaled_iters != scaled_iters_long) {
// Remove outer loop and safepoint (too few iterations)
remove_outer_loop_and_safepoint(igvn);
return;
}
jlong short_scaled_iters = LoopStripMiningIterShortLoop * ABS(stride);
const TypeInt* inner_iv_t = igvn->type(inner_iv_phi)->is_int();
jlong iter_estimate = (jlong)inner_iv_t->_hi - (jlong)inner_iv_t->_lo;
assert(iter_estimate > 0, "broken");
if ((jlong)scaled_iters != scaled_iters_long || iter_estimate <= short_scaled_iters) {
// Remove outer loop and safepoint (too few iterations)
if (iter_estimate <= short_scaled_iters) {
// Remove outer loop and safepoint: loop executes less than LoopStripMiningIterShortLoop
remove_outer_loop_and_safepoint(igvn);
return;
}