Avoid bounds checks in IDCD and IWHT #9

Shnatsel · 2023-10-03T16:57:00Z

No autovectorization, but at least the bounds checks are gone.

Shnatsel · 2023-10-03T16:58:04Z

I don't know how to benchmark this change because the crate is not wired up to image (I think?) so my usual benchmarking harness doesn't work, and the crate doesn't contain any examples (understandably, for such an early stage).

fintelia

Do you know whether the argument is always exactly 16 entries? If so, we should assert the exact length rather than >= 16

fintelia · 2023-10-21T22:26:41Z

src/transform.rs

@@ -46,6 +49,9 @@ pub(crate) fn idct4x4(block: &mut [i32]) {

 // 14.3
 pub(crate) fn iwht4x4(block: &mut [i32]) {
+    // Perform one lenght check up front to avoid subsequent bounds checks in this function


nit: lenght -> length

Shnatsel · 2023-10-21T23:32:25Z

When I made this function accept [i32; 16] tests broke, and I did not know enough about the format to understand why. So I just put the most lenient assert in place that would get rid of the bounds checks.

Avoid bounds checks in IDCD and IWHT

bd03888

fintelia reviewed Oct 21, 2023

View reviewed changes

fix typo

77f5d43

fintelia merged commit a4d00d0 into image-rs:main Oct 22, 2023
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Avoid bounds checks in IDCD and IWHT #9

Avoid bounds checks in IDCD and IWHT #9

Shnatsel commented Oct 3, 2023

Shnatsel commented Oct 3, 2023

fintelia left a comment

fintelia Oct 21, 2023

Shnatsel commented Oct 21, 2023

Avoid bounds checks in IDCD and IWHT #9

Avoid bounds checks in IDCD and IWHT #9

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Shnatsel commented Oct 3, 2023

Shnatsel commented Oct 3, 2023

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fintelia Oct 21, 2023

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Shnatsel commented Oct 21, 2023