JDK-8074869 : C2 code generator can replace -0.0f with +0.0f on Linux
- Type: Bug
- Component: hotspot
- Sub-Component: compiler
- Affected Version: 7u76,8u60,9
- Priority: P3
- Status: Resolved
- Resolution: Fixed
- OS: linux
- CPU: generic
- Submitted: 2015-03-10
- Updated: 2015-11-10
- Resolved: 2015-03-14
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| JDK 7 | JDK 8 | JDK 9 |
|---|---|---|
| 7u85Fixed | 8u60Fixed  |
9 b57Fixed |
Description
On Linux, the C2 code generator can replace the value -0.0f with +0.0f (and also the value -0.0d with +0.0d). The reason is that in some *.ad files both the value -0.0f and +0.0f is treated as being 0.0 and can therefore be replaced with an immediate +0.0f embedded into an instruction. For example, in the sparc.ad file, the 'fpclass' function is used to decide if a float node's content is +0.0: predicate((n->getf() == 0) && (fpclass(n->getf()) == FP_PZERO)); On Solaris, 'fpclass' returns FP_PZERO if the parameter is +0.0f and FP_NZERO if the parameter is -0.0f. On Linux, however, 'fpclass' is not available and therefore 'fpclassify' is used. 'fpclassify' does not distinguish between ��0.0f, it returns FP_ZERO for both +0.0f and -0.0f.
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