Thanks so much Silviu. I love this tool - I had seen it before, but didn't
realize it also supported go language. Thanks so much for bringing it up -
it should help me do more investigation on my own faster.
I used it to compare the asm output, and I got the same thing as when I did
go build -gcflags "-S" num_conversion.go
i.e. it leads me to conclude, as I suspected, that conversion from int to
uint is free (no-op at runtime).
However, I get concerned that my proof may be insufficient, or there may be
other reason why the asm looks same, and that is why I wanted a definitive
answer from someone familiar with the internals.
On Saturday, November 24, 2018 at 11:28:43 AM UTC-5, Silviu Capota Mera
wrote:
>
> A very nice tool from Matt Godbolt (and team of volunteers):
> https://godbolt.org/z/4nt5cJ
>
> You can switch compiler version (e.g. Go 1.4, 1.7, 1.9, 1.11, tip, etc)
> and/or gccgo, take a look at variations, etc
>
> On Saturday, 24 November 2018 11:07:51 UTC-5, Jan Mercl wrote:
>>
>> On Sat, Nov 24, 2018 at 4:31 PM Ugorji Nwoke <ugo...@gmail.com> wrote:
>>
>> > Jan, you and I have the same understanding i.e. float <-> int is
>> obviously non-free, but I can't think of why int <-> uint will not be free.
>> However, I want someone with knowledge of the
>> > compiler/runtime/codegeneration/SSA internals that can give me a
>> definitive answer.
>>
>> Any correct compiler is an implementation of the language specification.
>> From the language specification it follows that the compiler _may_ check
>> that - for example - 42 != 314 or 278 == 278 while performing the 'uint'
>> <-> 'int" conversion. It may also try to factor M4170639287. The question
>> is why to do so when nothing of that is mandated by the language
>> specification for a correct implementation?
>>
>> The next reasonable step is to assume Occam's razor is a thing.
>>
>> --
>>
>> -j
>>
>
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