JDK-8073670 : TypeF::eq and TypeD::eq do not handle NaNs correctly
- Type: Bug
- Component: hotspot
- Sub-Component: compiler
- Affected Version: 8u112,9
- Priority: P1
- Status: Closed
- Resolution: Fixed
- OS: generic
- CPU: generic
- Submitted: 2015-02-23
- Updated: 2018-02-15
- Resolved: 2015-02-28
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| JDK 8 | JDK 9 |
|---|---|
8u162Fixed  |
9 b55Fixed |
Description
Hi Chris,
i"ve found a problem with differet kinds of NaN nodes in the C2 compiler. In C2 different NaN nodes are merged together where in C1 and interpreter it does not and treats them as different NaNs. To make C2 consistent to C1, i've prepared this patch
The java spec does not define any behavior how the NaNs need to be normalized. But we can be sure, that we hardly break any existing javacode which relies on this behavior, because the behavior of C1 and C2 generated code diverges.
Test to run: java -cp ./bin/ -Xcomp -XX:-TieredCompilation NaNTest
Expected result:
Test Successful
Error result:
Exception in thread "main" java.lang.InternalError: 0x7ff00000000007a2 0x7ff00000000007a2
at NaNTest.main(NaNTest.java:26)
Patch to fix this issue:
diff -r b300d1f6e817 src/share/vm/opto/type.cpp
--- a/src/share/vm/opto/type.cpp Fri Jan 30 20:52:39 2015 +0100
+++ b/src/share/vm/opto/type.cpp Mon Feb 16 16:01:35 2015 +0100
@@ -1092,8 +1092,10 @@
bool TypeD::eq( const Type *t ) const {
if( g_isnan(_d) ||
g_isnan(t->getd()) ) {
- // One or both are NANs. If both are NANs return true, else false.
- return (g_isnan(_d) && g_isnan(t->getd()));
+ // it is important, when two different NaNs are used in one method, the NaNs are treated
+ // as different NaNs (as C1 does)
+ jdouble td = t->getd();
+ return *((jlong*)(&_d)) == *(jlong*)(&td);
}
if (_d == t->getd()) {
// (NaN is impossible at this point, since it is not equal even to itself)
Stefan
Comments
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