On Tuesday, 23 May 2017 at 13:27:42 UTC, Andrei Alexandrescu wrote:
On 5/22/17 4:51 PM, Johan Engelen wrote:
On Monday, 22 May 2017 at 15:05:24 UTC, Andrei Alexandrescu wrote:
[...]

A fun read!

"(Late at night, I double checked. Mozilla’s CheckedInt is just as bad as I remembered. They do a division to test for multiplication overflow. Come on, put a line of assembler in there! Portability is worth a price, just not any price.)"

Shocked: do you use assembly in Checked and cripple the optimizer?!?! Luckily, no. But LDC and GDC do create the `seto` instruction I think you were hinting at:
https://godbolt.org/g/0jUhgs

(LDC doesn't do as good as it could, https://github.com/ldc-developers/ldc/issues/2131)

Thanks! Yes, seto is what I thought of - one way or another, it gets down to using a bit of machine-specific code to get there. I'll note that dmd does not generate seto (why?): https://goo.gl/nRjNMy. -- Andrei

it does this
overflow_flag = 0
op
if (overflowed)
{
  overflow_flag = 1;
}

this can in some circumstances be faster then using seto!
If the inliner does a good enough job :)

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