npendleton

Hah, great point!

This is so cool!

Terrible nitpick, but this is actually 3 operations, not instructions. On x86 you get 4:

  is_leap_year_fast:
        imul    eax, edi, 1073750999
        and     eax, -1073614833
        cmp     eax, 126977
        setb    al
        ret

On ARM you get a bit more due to instruction encoding:

  is_leap_year_fast:
        ldr     r1, .LCPI0_0
        mul     r0, r0, r1
        ldr     r1, .LCPI0_1
        and     r1, r0, r1
        mov     r0, #0
        cmp     r1, #126976
        movwls  r0, #1
        bx      lr
  .LCPI0_0:
        .long   1073750999
  .LCPI0_1:
        .long   3221352463

Compiler explorer reference: https://godbolt.org/z/7ajYqbT9z

npendleton

去年discuss

Whoa, it looks like my old patch is getting fixed up properly now! We might be getting this feature https://lore.kernel.org/git/20250501214057.371711-4-gitster@...

npendleton

去年discuss

I agree! Unfortunately the best information appears to be in the individual series datasheets, however I did find this page to be helpful: https://products.espressif.com/#/product-selector

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