make use of nontrapping-fptoint, add tunnel.cwa as reference

examples/c/cart.c

@@ -16,7 +16,7 @@ void upd() {
         float t = time() * 63.0f;
         float x = (float)(i % 320 - 160);
         float y = (float)(i / 320 - 120);
-        float d = 40000.0f / sqrt(x * x + y * y + 1.0f);
+        float d = 40000.0f / sqrt(x * x + y * y);
         float u = atan2(x, y) * 512.0f / 3.141f;
         unsigned char c = (unsigned char)((int)(d + t * 2.0f) ^ (int)(u + t)) >> 4;
         FRAMEBUFFER[i] = c;

examples/curlywas/tunnel.cwa

@@ -0,0 +1,19 @@
+import "env.memory" memory(4);
+
+import "env.atan2" fn atan2(f32, f32) -> f32;
+import "env.time" fn time() -> f32;
+
+export fn upd() {
+    let i: i32;
+    loop pixels {
+        let inline t = time() * 63 as f32;
+        let lazy x = (i % 320 - 160) as f32;
+        let lazy y = (i / 320 - 120) as f32;
+        let inline d = 40000 as f32 / sqrt(x * x + y * y);
+        let inline u = atan2(x, y) * (512.0 / 3.141);
+        let inline c = ((i32.trunc_sat_f32_s(d + t * 2 as f32) ^ i32.trunc_sat_f32_s(u + t)) & 255) >> 4;
+        i?120 = c;
+
+        branch_if (i := i + 1) < 320*240: pixels;
+    }
+}

examples/rust/build.sh

@@ -1,4 +1,4 @@
-rustc --target=wasm32-unknown-unknown --crate-type cdylib -C opt-level="z" -C "link-args=--import-memory --initial-memory=262144 -zstack-size=90000" -o tunnel.wasm tunnel.rs && \
+rustc --target=wasm32-unknown-unknown -C target-feature=+nontrapping-fptoint --crate-type cdylib -C opt-level="z" -C "link-args=--import-memory --initial-memory=262144 -zstack-size=90000" -o tunnel.wasm tunnel.rs && \
 uw8 filter-exports tunnel.wasm tunnel.wasm && \
 wasm-opt -Oz --strip-producers -o tunnel.wasm tunnel.wasm && \
 uw8 pack -l 9 tunnel.wasm tunnel.uw8

examples/rust/tunnel.rs

@@ -27,15 +27,6 @@ fn sqrt(v: f32) -> f32 {
     unsafe { core::intrinsics::sqrtf32(v) }
 }
 
-fn ftoi(v: f32) -> i32 {
-    // The compiler is allowed to do bad things to our code if this
-    // ever results in a value that doesn't fit in an i32.
-    // (the joy of undefined behavior)
-    // But that would trap in wasm anyway, so we don't really
-    // care.
-    unsafe { v.to_int_unchecked() }
-}
-
 #[no_mangle]
 pub fn upd() {
     let mut i: i32 = 0;
@@ -43,9 +34,9 @@ pub fn upd() {
         let t = time() * 63.;
         let x = (i % 320 - 160) as f32;
         let y = (i / 320 - 120) as f32;
-        let d = 40000 as f32 / sqrt(x * x + y * y + 1.);
+        let d = 40000 as f32 / sqrt(x * x + y * y);
         let u = atan2(x, y) * 512. / 3.141;
-        let c = (ftoi(d + t * 2.) ^ ftoi(u + t)) as u8 >> 4;
+        let c = ((d + t * 2.) as i32 ^ (u + t) as i32) as u8 >> 4;
         unsafe {
             *((120 + i) as *mut u8) = c;
         }

examples/zig/main.zig

@@ -9,7 +9,7 @@ export fn upd() void {
         var t = time() * 63.0;
         var x = @intToFloat(f32, (@intCast(i32, i % 320) - 160));
         var y = @intToFloat(f32, (@intCast(i32, i / 320) - 120));
-        var d = 40000.0 / @sqrt(x * x + y * y + 1.0);
+        var d = 40000.0 / @sqrt(x * x + y * y);
         var u = atan2(x, y) * 512.0 / 3.141;
         var c = @intCast(u8, (@floatToInt(i32, d + t * 2.0) ^ @floatToInt(i32, u + t)) & 255) >> 4;