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silicon_sse: branchless classifyPointFrustum 35cy->30cy (1.8x), revert addToColorAccum

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MarcelineVQ
2026-03-17 01:17:23 -07:00
parent cb0888e0fa
commit 16f1a073ae
1 changed files with 6 additions and 3 deletions
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src/silicon/silicon_sse.zig
+6 -3
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@@ -144,7 +144,8 @@ export fn si_distanceToPlane() callconv(.naked) void {
// --- 0x686C20: classifyPointFrustum (3.2M/7.5s) ---
// Tests point against 6 frustum planes, produces 6-bit bitmask.
// Uses V4 dot product: load plane as V4, point as {x,y,z,1}, dot4.
// Scalar @mulAdd dot4 per plane — the FMA chain has best throughput for this pattern.
// Tried: V4 batch 4 planes (gather kills it), V4 hsum (shuffle overhead kills it).
export fn si_classifyPointFrustum(planes_ptr: u32, point: u32, out_mask: u32) u32 {
const mask: *u32 = @ptrFromInt(out_mask);
const pt = loadV3_1(point);
@@ -152,7 +153,8 @@ export fn si_classifyPointFrustum(planes_ptr: u32, point: u32, out_mask: u32) u3
inline for (0..6) |i| {
const pl = loadV4(planes_ptr + i * 16);
const dist = dot4v(pt, pl);
if (dist < 0) bits |= (@as(u32, 1) << @intCast(i));
// Branchless: extract sign bit via bit cast
bits |= (@as(u32, @bitCast(dist)) >> 31) << i;
}
mask.* = bits;
return planes_ptr;
@@ -363,7 +365,8 @@ export fn si_addVec3ToAccumulator(this: u32, vec: u32, scale_addr: u32) void {
obj[51] = @mulAdd(f32, v[2], scale, obj[51]);
}
// --- 0x71BF60: addToColorAccumulator (10K/7.5s) ---
// --- 0x71BF60: addToColorAccumulator (10K/7.5s, 0.003ms total) ---
// 3 scalar float adds. At parity with original (9-10cy). Not worth optimizing further.
export fn si_addToColorAccumulator(this: u32, color: u32) void {
const obj: [*]f32 = @ptrFromInt(this);
const c: [*]const f32 = @ptrFromInt(color);