RFR: 8266028: C2 computes -0.0 for Math.pow(-0.0, 0.5)
jiefu at openjdk.java.net
Tue Apr 27 08:34:43 UTC 2021
C2 computes -0.0 for Math.pow(-0.0, 0.5) which should be 0.0 according to the API specs.
This bug was found while I was implementing the same optimization for x86_32 (JDK-8265940).
The reason is that CmpDNode  doesn't distinguish -0.0 from 0.0.
Math.pow(-0.0, 0.5) was replaced with Math.sqrt(-0.0) incorrectly since CmpDNode says -0.0 < 0.0 if false.
The fix excludes C2's optimization for x=0.0/-0.0.
And the jtreg test has been improved to make sure the corner cases are covered by the compilers.
- 8266028: C2 computes -0.0 for Math.pow(-0.0, 0.5)
Stats: 21 lines in 2 files changed: 9 ins; 11 del; 1 mod
Fetch: git fetch https://git.openjdk.java.net/jdk pull/3712/head:pull/3712
More information about the hotspot-compiler-dev