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8317723: C2: CountedLoopEndNodes and Zero Trip Guards are wrongly tre…
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…ated as Runtime Predicate

Reviewed-by: thartmann, epeter
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chhagedorn committed Nov 16, 2023
1 parent eaa4417 commit 2db9ea9
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Showing 5 changed files with 127 additions and 1 deletion.
1 change: 1 addition & 0 deletions src/hotspot/share/opto/cfgnode.hpp
Original file line number Diff line number Diff line change
Expand Up @@ -431,6 +431,7 @@ class IfNode : public MultiBranchNode {
Node* fold_compares(PhaseIterGVN* phase);
static Node* up_one_dom(Node* curr, bool linear_only = false);
Node* dominated_by(Node* prev_dom, PhaseIterGVN* igvn);
bool is_zero_trip_guard() const;

// Takes the type of val and filters it through the test represented
// by if_proj and returns a more refined type if one is produced.
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7 changes: 7 additions & 0 deletions src/hotspot/share/opto/ifnode.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -1774,6 +1774,13 @@ Node* IfProjNode::Identity(PhaseGVN* phase) {
return this;
}

bool IfNode::is_zero_trip_guard() const {
if (in(1)->is_Bool() && in(1)->in(1)->is_Cmp()) {
return in(1)->in(1)->in(1)->Opcode() == Op_OpaqueZeroTripGuard;
}
return false;
}

#ifndef PRODUCT
//------------------------------dump_spec--------------------------------------
void IfNode::dump_spec(outputStream *st) const {
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16 changes: 15 additions & 1 deletion src/hotspot/share/opto/predicates.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -77,13 +77,26 @@ Deoptimization::DeoptReason RuntimePredicate::uncommon_trap_reason(IfProjNode* i
}

bool RuntimePredicate::is_success_proj(Node* node, Deoptimization::DeoptReason deopt_reason) {
if (node->is_IfProj() && !node->in(0)->is_ParsePredicate()) {
if (may_be_runtime_predicate_if(node)) {
return deopt_reason == uncommon_trap_reason(node->as_IfProj());
} else {
return false;
}
}

// A Runtime Predicate must have an If or a RangeCheck node, while the If should not be a zero trip guard check.
bool RuntimePredicate::may_be_runtime_predicate_if(Node* node) {
if (node->is_IfProj()) {
const IfNode* if_node = node->in(0)->as_If();
const int opcode_if = if_node->Opcode();
if ((opcode_if == Op_If && !if_node->is_zero_trip_guard())
|| opcode_if == Op_RangeCheck) {
return true;
}
}
return false;
}

ParsePredicateIterator::ParsePredicateIterator(const Predicates& predicates) : _current_index(0) {
const PredicateBlock* loop_limit_check_predicate_block = predicates.loop_limit_check_predicate_block();
if (loop_limit_check_predicate_block->has_parse_predicate()) {
Expand Down Expand Up @@ -118,6 +131,7 @@ void PredicateBlock::verify_block() {
const int opcode = next->Opcode();
assert(next->is_IfProj() || opcode == Op_If || opcode == Op_RangeCheck,
"Regular Predicates consist of an IfProj and an If or RangeCheck node");
assert(opcode != Op_If || !next->as_If()->is_zero_trip_guard(), "should not be zero trip guard");
next = next->in(0);
}
}
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1 change: 1 addition & 0 deletions src/hotspot/share/opto/predicates.hpp
Original file line number Diff line number Diff line change
Expand Up @@ -257,6 +257,7 @@ class ParsePredicate : public StackObj {
// Utility class for queries on Runtime Predicates.
class RuntimePredicate : public StackObj {
static Deoptimization::DeoptReason uncommon_trap_reason(IfProjNode* if_proj);
static bool may_be_runtime_predicate_if(Node* node);

public:
static bool is_success_proj(Node* node, Deoptimization::DeoptReason deopt_reason);
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Original file line number Diff line number Diff line change
@@ -0,0 +1,103 @@
/*
* Copyright (c) 2023, 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
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/

/*
* @test
* @bug 8317723
* @library /test/lib
* @summary Test that CountedLoopEndNodes and zero trip guard check If nodes are not treated as Runtime Predicates.
* @run main/othervm -XX:-TieredCompilation -Xbatch
* -XX:CompileCommand=compileonly,compiler.predicates.TestWrongRuntimePredicateDetection::test*
* compiler.predicates.TestWrongRuntimePredicateDetection
*/

package compiler.predicates;

public class TestWrongRuntimePredicateDetection {
static int[] iArr = new int[50];
static long instanceCount;
static boolean bFld = true;
static volatile byte byFld;
static long[][] lArrFld;


public static void main(String[] x) {
for (int i = 0; i < 1000; i++) {
testCountedLoopEndAsRuntimePredicate();
}
for (int i = 0; i < 10; i++) {
testZeroTripGuardAsRuntimePredicate();
}
}

static void testCountedLoopEndAsRuntimePredicate() {
int i22 = 7, i26, i28, i29 = 8, i31 = 1;
float f4;
do {
for (int i = 0; i < 10000; i++) {
if (bFld) {
break;
}
instanceCount = byFld;
}
for (i26 = 4; 80 > i26; i26 += 2) ;
} while (++i22 < 315);
i28 = 6;
while ((i28 -= 3) > 0) {
for (f4 = i28; f4 < 53; f4++) {
bFld = false;
}
instanceCount = i26;
do {
switch ((i26 >>> 1) % 2 * 5 + 6) {
case 12:
case 10:
lArrFld[i31][1] = i29;
}
} while (++i31 < 53);
}
}

static void testZeroTripGuardAsRuntimePredicate() {
int m;
int a[] = new int[50];
for (int j = 0; j < a.length; j++) {
a[j] = j;
}

for (int j = 4; j < 42; j++) {
for (int k = 1; k < 5; k++) {
iArr[1] = 34;
switch (j % 4) {
case 0:
iArr = iArr;
case 1:
case 3:
m = 3;
}
}
}
}

}

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