I tried d8 with --allow-natives-syntax --turbofan --print-opt-code flags
and following code but don't get any output.
function my_mod(n) {
if (n % 2 == 1)
return true;
return false;
}
my_mod(2);
my_mod(1);
my_mod(3);
%OptimizeFunctionOnNextCall(my_mod);
my_mod(100)
I'm not sure which flags to use here.
On Tuesday, March 11, 2025 at 5:35:11 PM UTC+7 Jakob Kummerow wrote:
> Why don't you test it and find out yourself?
>
>
> On Tue, Mar 11, 2025 at 10:20 AM Sỹ Trần Dũng <[email protected]> wrote:
>
>> I have a question regarding V8's compiler optimization, specifically
>> concerning the modulo 2 operation. In compilers like GCC and Clang, it's
>> common to see the operation n % 2 optimized to a bitwise AND (n & 1) or a
>> bit check instruction, as these are generally more efficient.
>>
>> I've been examining the bytecode generated by V8, and I've observed that
>> a modulo instruction is used for n % 2.
>>
>> [generated bytecode for function: my_mod (0x3de244c5b401
>> <SharedFunctionInfo my_mod>)]
>> Bytecode length: 17
>> Parameter count 2
>> Register count 1
>> Frame size 8
>> 23 S> 0x32c69b60dc80 @ 0 : 0b 03 Ldar a0
>> 29 E> 0x32c69b60dc82 @ 2 : 4b 02 00 ModSmi [2], [0]
>> 0x32c69b60dc85 @ 5 : c9 Star0
>> 0x32c69b60dc86 @ 6 : 0d 01 LdaSmi [1]
>> 33 E> 0x32c69b60dc88 @ 8 : 6f f9 01 TestEqual r0, [1]
>> 0x32c69b60dc8b @ 11 : 9e 04 JumpIfFalse [4]
>> (0x32c69b60dc8f @ 15)
>> 45 S> 0x32c69b60dc8d @ 13 : 11 LdaTrue
>> 57 S> 0x32c69b60dc8e @ 14 : ae Return
>> 64 S> 0x32c69b60dc8f @ 15 : 12 LdaFalse
>> 77 S> 0x32c69b60dc90 @ 16 : ae Return
>>
>> I'm curious if this behavior changes when the code is "heated" and
>> optimized by Turbofan.
>>
>> Could someone please tell whether Turbofan performs this particular
>> optimization?
>>
>> Thank you for your time and expertise.
>>
>> --
>>
>
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