Integrated: 8265917: Different values computed by C2 and interpreter/C1 for Math.pow(x, 2.0) on x86_32
jiefu at openjdk.java.net
Wed Apr 28 03:14:55 UTC 2021
On Sun, 25 Apr 2021 11:39:43 GMT, Jie Fu <jiefu at openjdk.org> wrote:
> Hi all,
> C2 may produce different results for Math.pow(x, 2.0) compared with interpreter/C1 on x86_32.
> E.g., for Math.pow(1.0 / 2047, 2.0):
> interpreter: 2.38651580386563E-7
> C2: 2.3865158038656307E-7
> The reason is that C2 will replace Math.pow(x, 2.0) with x*x.
> However, there is no such optimization for interpreter/C1 on x86_32.
> The fix just disables C2's opt for Math.pow(x, 2.0) on x86_32 since nobody (or very few people) would run x86_32.
> And we don't have a plan to implement such opt on x86_32.
> Another reason to fix this bug is that we need this patch to extend C2's opt for Math.pow(x, 0.5) on other platforms.
> Best regards,
This pull request has now been integrated.
Author: Jie Fu <jiefu at openjdk.org>
Stats: 66 lines in 2 files changed: 66 ins; 0 del; 0 mod
8265917: Different values computed by C2 and interpreter/C1 for Math.pow(x, 2.0) on x86_32
Reviewed-by: kvn, thartmann
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