Fix bug in sinking.

diku-dk · Feb 3, 2025 · 7ad26ab · 7ad26ab
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -33,6 +33,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 * `futhark fmt`: correct file name in parse errors.
 
+* A bug in the "sink" optimisation pass could cause compiler crashes.
+
 ## [0.25.26]
 
 ### Fixed

diff --git a/tests/sinking6.fut b/tests/sinking6.fut
@@ -0,0 +1,11 @@
+-- At one point this did an incorrect sinking due to not looking
+-- properly at WithAccs.
+
+def pointToRoller (model: [2]f32) (p: f32) : f32 =
+  let radius = model[0]
+  let alpha = model[1]
+  let p' = map (p *) [f32.sin alpha, 0.0]
+  in (p'[0] - radius) ** 2
+
+entry pointsToRollerGrad [n] (model: [2]f32) (pcd: [n]f32) : [2]f32 =
+  vjp (\m -> map (pointToRoller m) pcd |> f32.sum) model 1