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8324794: C2 SuperWord: do not ignore reductions in SuperWord::unrolling_analysis

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Reviewed-by: chagedorn, kvn
This commit is contained in:
Emanuel Peter 2024-01-30 20:14:20 +00:00
parent d51aaf6304
commit 11e28bd619
2 changed files with 13 additions and 3 deletions
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1
src/hotspot/share/opto/superword.cpp
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@ -177,7 +177,6 @@ void SuperWord::unrolling_analysis(int &local_loop_unroll_factor) {
for (uint i = 0; i < lpt()->_body.size(); i++) {
Node* n = lpt()->_body.at(i);
if (n == cl->incr() ||
is_marked_reduction(n) ||
n->is_AddP() ||
n->is_Cmp() ||
n->is_Bool() ||

15
test/hotspot/jtreg/compiler/loopopts/superword/TestUnorderedReductionPartialVectorization.java
View File

@ -1,5 +1,5 @@
/*
* Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2023, 2024, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@ -64,7 +64,7 @@ public class TestUnorderedReductionPartialVectorization {
IRNode.OR_REDUCTION_V, "> 0",},
applyIfCPUFeatureOr = {"avx2", "true"})
static long test1(int[] data, long sum) {
for (int i = 0; i < data.length; i++) {
for (int i = 0; i < data.length; i+=2) {
// Mixing int and long ops means we only end up allowing half of the int
// loads in one pack, and we have two int packs. The first pack has one
// of the pairs missing because of the store, which creates a dependency.
@ -77,6 +77,17 @@ public class TestUnorderedReductionPartialVectorization {
int v = data[i]; // int read
data[0] = 0; // ruin the first pack
sum |= v; // long reduction (and implicit cast from int to long)
// This example used to rely on that reductions were ignored in SuperWord::unrolling_analysis,
// and hence the largest data type in the loop was the ints. This would then unroll the doubles
// for twice the vector length, and this resulted in us having twice as many packs. Because of
// the store "data[0] = 0", the first packs were destroyed, since they do not have power of 2
// size.
// Now, we no longer ignore reductions, and now we unroll half as much before SuperWord. This
// means we would only get one pack per operation, and that one would get ruined, and we have
// no vectorization. We now ensure there are again 2 packs per operation with a 2x hand unroll.
int v2 = data[i + 1];
sum |= v2;
}
return sum;
}