8286638: C2: CmpU needs to do more precise over/underflow analysis

Reviewed-by: kvn, vlivanov, thartmann
This commit is contained in:
Emanuel Peter 2022-05-16 07:21:30 +00:00 committed by Tobias Hartmann
parent 46d208fb1c
commit 2d34acfec9
2 changed files with 61 additions and 5 deletions
src/hotspot/share/opto
test/hotspot/jtreg/compiler/rangechecks

@ -827,11 +827,10 @@ const Type* CmpUNode::Value(PhaseGVN* phase) const {
int w = MAX2(r0->_widen, r1->_widen); // _widen does not matter here
const TypeInt* tr1 = TypeInt::make(lo_tr1, hi_tr1, w);
const TypeInt* tr2 = TypeInt::make(lo_tr2, hi_tr2, w);
const Type* cmp1 = sub(tr1, t2);
const Type* cmp2 = sub(tr2, t2);
if (cmp1 == cmp2) {
return cmp1; // Hit!
}
const TypeInt* cmp1 = sub(tr1, t2)->is_int();
const TypeInt* cmp2 = sub(tr2, t2)->is_int();
// compute union, so that cmp handles all possible results from the two cases
return cmp1->meet(cmp2);
}
}
}

@ -0,0 +1,57 @@
/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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*
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*/
/*
* @test
* @bug 8286638
* @summary Dominator failure because ConvL2I node becomes TOP, kills data-flow, but range-check does not collapse
* due to insufficient overflow/underflow handling in CmpUNode::Value.
*
* @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+StressIGVN -Xcomp -XX:-TieredCompilation
* -XX:CompileCommand=compileonly,compiler.rangechecks.TestRangeCheckCmpUUnderflow::*
* -XX:RepeatCompilation=300
* compiler.rangechecks.TestRangeCheckCmpUUnderflow
*/
package compiler.rangechecks;
public class TestRangeCheckCmpUUnderflow {
volatile int a;
int b[];
float c[];
void e() {
int g, f, i;
for (g = 2;; g++) {
for (i = g; i < 1; i++) {
f = a;
c[i - 1] -= b[i];
}
}
}
public static void main(String[] args) {
try {
TestRangeCheckCmpUUnderflow j = new TestRangeCheckCmpUUnderflow();
j.e();
} catch (Exception ex) {}
}
}