libcore: Use LLVM intrinsics for floor; add a new Perlin noise benchmark. r=brson

src/libcore/f32.rs

@@ -56,7 +56,6 @@ delegate!(fn exp2(n: c_float) -> c_float = cmath::c_float_utils::exp2)
 delegate!(fn abs(n: c_float) -> c_float = cmath::c_float_utils::abs)
 delegate!(fn abs_sub(a: c_float, b: c_float) -> c_float =
     cmath::c_float_utils::abs_sub)
-delegate!(fn floor(n: c_float) -> c_float = cmath::c_float_utils::floor)
 delegate!(fn mul_add(a: c_float, b: c_float, c: c_float) -> c_float =
     cmath::c_float_utils::mul_add)
 delegate!(fn fmax(a: c_float, b: c_float) -> c_float =
@@ -141,6 +140,10 @@ pub pure fn ge(x: f32, y: f32) -> bool { return x >= y; }
 #[inline(always)]
 pub pure fn gt(x: f32, y: f32) -> bool { return x > y; }
 
+/// Returns `x` rounded down
+#[inline(always)]
+pub pure fn floor(x: f32) -> f32 { unsafe { floorf32(x) } }
+
 // FIXME (#1999): replace the predicates below with llvm intrinsics or
 // calls to the libmath macros in the rust runtime for performance.
 
@@ -298,6 +301,11 @@ impl f32: num::One {
     static pure fn one() -> f32 { 1.0 }
 }
 
+#[abi="rust-intrinsic"]
+pub extern {
+    fn floorf32(val: f32) -> f32;
+}
+
 //
 // Local Variables:
 // mode: rust

src/libcore/f64.rs

@@ -57,7 +57,6 @@ delegate!(fn exp2(n: c_double) -> c_double = cmath::c_double_utils::exp2)
 delegate!(fn abs(n: c_double) -> c_double = cmath::c_double_utils::abs)
 delegate!(fn abs_sub(a: c_double, b: c_double) -> c_double =
     cmath::c_double_utils::abs_sub)
-delegate!(fn floor(n: c_double) -> c_double = cmath::c_double_utils::floor)
 delegate!(fn mul_add(a: c_double, b: c_double, c: c_double) -> c_double =
     cmath::c_double_utils::mul_add)
 delegate!(fn fmax(a: c_double, b: c_double) -> c_double =
@@ -210,12 +209,16 @@ pub pure fn is_infinite(x: f64) -> bool {
     return x == infinity || x == neg_infinity;
 }
 
-/// Returns true if `x`is a finite number
+/// Returns true if `x` is a finite number
 #[inline(always)]
 pub pure fn is_finite(x: f64) -> bool {
     return !(is_NaN(x) || is_infinite(x));
 }
 
+/// Returns `x` rounded down
+#[inline(always)]
+pub pure fn floor(x: f64) -> f64 { unsafe { floorf64(x) } }
+
 // FIXME (#1999): add is_normal, is_subnormal, and fpclassify
 
 /* Module: consts */
@@ -322,6 +325,11 @@ impl f64: num::One {
     static pure fn one() -> f64 { 1.0 }
 }
 
+#[abi="rust-intrinsic"]
+pub extern {
+    fn floorf64(val: f64) -> f64;
+}
+
 //
 // Local Variables:
 // mode: rust

src/test/bench/noise.rs

@@ -0,0 +1,110 @@
+// Perlin noise benchmark from https://gist.github.com/1170424
+
+struct Vec2 {
+    x: f32,
+    y: f32,
+}
+
+fn lerp(a: f32, b: f32, v: f32) -> f32  { a * (1.0 - v) + b * v }
+fn smooth(v: f32) -> f32                { v * v * (3.0 - 2.0 * v) }
+
+fn random_gradient(r: rand::Rng) -> Vec2 {
+    let v = r.gen_float() * float::consts::pi * 2.0;
+    Vec2{
+        x: float::cos(v) as f32,
+        y: float::sin(v) as f32,
+    }
+}
+
+fn gradient(orig: Vec2, grad: Vec2, p: Vec2) -> f32 {
+    let sp = Vec2{x: p.x - orig.x, y: p.y - orig.y};
+    grad.x * sp.x + grad.y + sp.y
+}
+
+struct Noise2DContext {
+    rgradients: [Vec2 * 256],
+    permutations: [int * 256],
+}
+
+fn Noise2DContext() -> ~Noise2DContext {
+    let r = rand::Rng();
+    let mut rgradients = [ Vec2 { x: 0.0, y: 0.0 }, ..256 ];
+    for int::range(0, 256) |i| { rgradients[i] = random_gradient(r); }
+    let mut permutations = [ 0, ..256 ];
+    for int::range(0, 256) |i| { permutations[i] = i; }
+    r.shuffle_mut(permutations);
+
+    ~Noise2DContext{
+        rgradients: move rgradients,
+        permutations: move permutations,
+    }
+}
+
+impl Noise2DContext {
+    #[inline(always)]
+    fn get_gradient(&self, x: int, y: int) -> Vec2 {
+        let idx = self.permutations[x & 255] + self.permutations[y & 255];
+        self.rgradients[idx & 255]
+    }
+
+    #[inline(always)]
+    fn get_gradients(&self, gradients: &mut [Vec2 * 4], origins: &mut [Vec2 * 4], x: f32, y: f32) {
+        let x0f = f32::floor(x);
+        let y0f = f32::floor(y);
+        let x0 = x0f as int;
+        let y0 = y0f as int;
+        let x1 = x0 + 1;
+        let y1 = y0 + 1;
+
+        gradients[0] = self.get_gradient(x0, y0);
+        gradients[1] = self.get_gradient(x1, y0);
+        gradients[2] = self.get_gradient(x0, y1);
+        gradients[3] = self.get_gradient(x1, y1);
+
+        origins[0] = Vec2{x: x0f + 0.0, y: y0f + 0.0};
+        origins[1] = Vec2{x: x0f + 1.0, y: y0f + 0.0};
+        origins[2] = Vec2{x: x0f + 0.0, y: y0f + 1.0};
+        origins[3] = Vec2{x: x0f + 1.0, y: y0f + 1.0};
+    }
+
+    fn get(&self, x: f32, y: f32) -> f32 {
+        let p = Vec2{x: x, y: y};
+        let mut gradients = [ Vec2 { x: 0.0, y: 0.0 }, ..4 ];
+        let mut origins = [ Vec2 { x: 0.0, y: 0.0 }, ..4 ];
+        self.get_gradients(&mut gradients, &mut origins, x, y);
+        let v0 = gradient(origins[0], gradients[0], p);
+        let v1 = gradient(origins[1], gradients[1], p);
+        let v2 = gradient(origins[2], gradients[2], p);
+        let v3 = gradient(origins[3], gradients[3], p);
+        let fx = smooth(x - origins[0].x);
+        let vx0 = lerp(v0, v1, fx);
+        let vx1 = lerp(v2, v3, fx);
+        let fy = smooth(y - origins[0].y);
+        lerp(vx0, vx1, fy)
+    }
+}
+
+fn main() {
+    let symbols = [" ", "░", "▒", "▓", "█", "█"];
+    let mut pixels = vec::from_elem(256*256, 0f32);
+    let n2d = Noise2DContext();
+    for int::range(0, 100) |_| {
+        for int::range(0, 256) |y| {
+            for int::range(0, 256) |x| {
+                let v = n2d.get(
+                    x as f32 * 0.1f32,
+                    y as f32 * 0.1f32
+                ) * 0.5f32 + 0.5f32;
+                pixels[y*256+x] = v;
+            };
+        };
+    };
+
+    /*for int::range(0, 256) |y| {
+        for int::range(0, 256) |x| {
+            io::print(symbols[pixels[y*256+x] / 0.2f32 as int]);
+        }
+        io::println("");
+    }*/
+}
+