On Sat, 18 Mar 2023 17:06:52 GMT, jmehrens <d...@openjdk.org> wrote:
>> We could, but benchmarks show no performance improvements over the current
>> PR. I think the current code is perhaps slightly more readable.
>
> Does non-short-circuit logical AND operator perform similar to baseline? In
> this very specific case there is no risk of side effects due to method calls,
> no risk of null pointer exception because of primitives, and there is not an
> excessive amount of conditions. Therefore, I would think either `&` or `&&`
> are viable options.
>
> `if (ch >= 0 & ch <= 0xFF) {`
>
> I ask just for the sake of my own learning on this topic as it relates to
> performance as opposed to code readability preferences.
Both choices of operators en up with identical generated code on my Intel Mac.
For reference, I did a comparison between the generated code for the current
code, and the one in this PR:
Current generated code start like this:
movl %eax, -0x14000(%rsp)
pushq %rbp
subq $0x20, %rsp
cmpl $1, 0x20(%r15)
jne 0x119cae072
movl %esi, %r11d
shrl $8, %r11d
testl %r11d, %r11d
jne 0x119cae043
movabsq $0x70fe03c90, %rax ; {oop(a
'java/lang/CharacterDataLatin1'{0x000000070fe03c90})}
```
While the PR generated code starts like this:
movl %eax, -0x14000(%rsp)
pushq %rbp
subq $0x20, %rsp
cmpl $1, 0x20(%r15)
jne 0x1171d41f2
nopw (%rax, %rax)
cmpl $0x100, %esi
jae 0x1171d41c5
movabsq $0x70fe03c90, %rax ; {oop(a
'java/lang/CharacterDataLatin1'{0x000000070fe03c90})}
The rest of the code seems identical.
-------------
PR: https://git.openjdk.org/jdk/pull/13040
