From fe5f531c3f35767c4614c1c0e76c92e4b0630229 Mon Sep 17 00:00:00 2001
From: ark <adrian@forn.dk>
Date: Sat, 23 May 2026 16:48:04 +0200
Subject: [PATCH] perf: hoist tile/clamp out of highp sampler inner loop

---
 src/pipeline/highp.rs | 91 ++++++++++++++-----------------------------
 1 file changed, 30 insertions(+), 61 deletions(-)

diff --git a/src/pipeline/highp.rs b/src/pipeline/highp.rs
index 214e31a..9ce3111 100644
--- a/src/pipeline/highp.rs
+++ b/src/pipeline/highp.rs
@@ -747,7 +747,7 @@ fn bilinear(p: &mut Pipeline) {
     let wx = [one - fx, fx];
     let wy = [one - fy, fy];
 
-    sampler_2x2(p.pixmap_src, &p.ctx.sampler, x, y, &wx, &wy, &mut p.r, &mut p.g, &mut p.b, &mut p.a);
+    sampler::<2>(p.pixmap_src, &p.ctx.sampler, x, y, &wx, &wy, &mut p.r, &mut p.g, &mut p.b, &mut p.a);
 
     p.next_stage();
 }
@@ -761,7 +761,7 @@ fn bicubic(p: &mut Pipeline) {
     let wx = [bicubic_far(one - fx), bicubic_near(one - fx), bicubic_near(fx), bicubic_far(fx)];
     let wy = [bicubic_far(one - fy), bicubic_near(one - fy), bicubic_near(fy), bicubic_far(fy)];
 
-    sampler_4x4(p.pixmap_src, &p.ctx.sampler, x, y, &wx, &wy, &mut p.r, &mut p.g, &mut p.b, &mut p.a);
+    sampler::<4>(p.pixmap_src, &p.ctx.sampler, x, y, &wx, &wy, &mut p.r, &mut p.g, &mut p.b, &mut p.a);
 
     p.next_stage();
 }
@@ -795,11 +795,11 @@ fn bicubic_far(t: f32x8) -> f32x8 {
 }
 
 #[inline(always)]
-fn sampler_2x2(
+fn sampler<const N: usize>(
     pixmap: PixmapRef,
     ctx: &super::SamplerCtx,
     cx: f32x8, cy: f32x8,
-    wx: &[f32x8; 2], wy: &[f32x8; 2],
+    wx: &[f32x8; N], wy: &[f32x8; N],
     r: &mut f32x8, g: &mut f32x8, b: &mut f32x8, a: &mut f32x8,
 ) {
     *r = f32x8::default();
@@ -808,80 +808,49 @@ fn sampler_2x2(
     *a = f32x8::default();
 
     let one = f32x8::splat(1.0);
-    let start = -0.5;
-    let mut y = cy + f32x8::splat(start);
-    for j in 0..2 {
-        let mut x = cx + f32x8::splat(start);
-        for i in 0..2 {
-            let mut rr = f32x8::default();
-            let mut gg = f32x8::default();
-            let mut bb = f32x8::default();
-            let mut aa = f32x8::default();
-            sample(pixmap, ctx, x,y, &mut rr, &mut gg, &mut bb, &mut aa);
-
-            let w = wx[i] * wy[j];
-            *r = mad(w, rr, *r);
-            *g = mad(w, gg, *g);
-            *b = mad(w, bb, *b);
-            *a = mad(w, aa, *a);
-
-            x += one;
-        }
-
+    let start = f32x8::splat(-((N - 1) as f32) / 2.0);
+    let w = pixmap.width() as f32;
+    let h = pixmap.height() as f32;
+    let w_lim = f32x8::splat(ulp_sub(w));
+    let h_lim = f32x8::splat(ulp_sub(h));
+    let zero = f32x8::default();
+    let stride = i32x8::splat(pixmap.width() as i32);
+
+    // per-axis hoist: N tile_x + N tile_y instead of N*N + N*N. tile() is opaque
+    // to llvm across SpreadMode, so it never gets cse'd from the inner loop.
+    let mut tx_int = [i32x8::default(); N];
+    let mut ty_off = [i32x8::default(); N];
+    let mut x = cx + start;
+    let mut y = cy + start;
+    for i in 0..N {
+        let t = tile(x, ctx.spread_mode, w, ctx.inv_width);
+        tx_int[i] = t.max(zero).min(w_lim).trunc_int();
+        x += one;
+    }
+    for j in 0..N {
+        let t = tile(y, ctx.spread_mode, h, ctx.inv_height);
+        ty_off[j] = t.max(zero).min(h_lim).trunc_int() * stride;
         y += one;
     }
-}
-
-#[inline(always)]
-fn sampler_4x4(
-    pixmap: PixmapRef,
-    ctx: &super::SamplerCtx,
-    cx: f32x8, cy: f32x8,
-    wx: &[f32x8; 4], wy: &[f32x8; 4],
-    r: &mut f32x8, g: &mut f32x8, b: &mut f32x8, a: &mut f32x8,
-) {
-    *r = f32x8::default();
-    *g = f32x8::default();
-    *b = f32x8::default();
-    *a = f32x8::default();
 
-    let one = f32x8::splat(1.0);
-    let start = -1.5;
-    let mut y = cy + f32x8::splat(start);
-    for j in 0..4 {
-        let mut x = cx + f32x8::splat(start);
-        for i in 0..4 {
+    for j in 0..N {
+        for i in 0..N {
+            let ix = (ty_off[j] + tx_int[i]).to_u32x8_bitcast();
             let mut rr = f32x8::default();
             let mut gg = f32x8::default();
             let mut bb = f32x8::default();
             let mut aa = f32x8::default();
-            sample(pixmap, ctx, x,y, &mut rr, &mut gg, &mut bb, &mut aa);
+            load_8888(&pixmap.gather(ix), &mut rr, &mut gg, &mut bb, &mut aa);
 
             let w = wx[i] * wy[j];
             *r = mad(w, rr, *r);
             *g = mad(w, gg, *g);
             *b = mad(w, bb, *b);
             *a = mad(w, aa, *a);
-
-            x += one;
         }
-
-        y += one;
     }
 }
 
-#[inline(always)]
-fn sample(
-    pixmap: PixmapRef, ctx: &super::SamplerCtx, mut x: f32x8, mut y: f32x8,
-    r: &mut f32x8, g: &mut f32x8, b: &mut f32x8, a: &mut f32x8,
-) {
-    x = tile(x, ctx.spread_mode, pixmap.width() as f32, ctx.inv_width);
-    y = tile(y, ctx.spread_mode, pixmap.height() as f32, ctx.inv_height);
-
-    let ix = gather_ix(pixmap, x, y);
-    load_8888(&pixmap.gather(ix), r, g, b, a);
-}
-
 #[inline(always)]
 fn tile(v: f32x8, mode: SpreadMode, limit: f32, inv_limit: f32) -> f32x8 {
     match mode {