use log2

gfx-rs · Jan 31, 2023 · 254e806 · 254e806
1 parent 05f2649
commit 254e806
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Showing 2 changed files with 8 additions and 10 deletions.
diff --git a/src/back/glsl/mod.rs b/src/back/glsl/mod.rs
@@ -2930,8 +2930,6 @@ impl<'a, W: Write> Writer<'a, W> {
                     Mf::Determinant => "determinant",
                     // bits
                     Mf::CountLeadingZeros => {
-                        use std::f32::consts::LOG2_E;
-
                         match *ctx.info[arg].ty.inner_with(&self.module.types) {
                             crate::TypeInner::Vector { size, kind, .. } => {
                                 let s = back::vector_size_str(size);
@@ -2942,9 +2940,9 @@ impl<'a, W: Write> Writer<'a, W> {
                                     write!(self.out, "ivec{s}(")?;
                                 }
 
-                                write!(self.out, "mix(vec{s}(31.0) - floor(log(vec{s}(")?;
+                                write!(self.out, "mix(vec{s}(31.0) - floor(log2(vec{s}(")?;
                                 self.write_expr(arg, ctx)?;
-                                write!(self.out, ") + 0.5) * {LOG2_E}), ")?;
+                                write!(self.out, ") + 0.5)), ")?;
 
                                 if let crate::ScalarKind::Uint = kind {
                                     write!(self.out, "vec{s}(32.0), lessThanEqual(")?;
@@ -2970,9 +2968,9 @@ impl<'a, W: Write> Writer<'a, W> {
                                     write!(self.out, " == 0 ? 32 : 0) : int(")?;
                                 }
 
-                                write!(self.out, "31.0 - floor(log(float(")?;
+                                write!(self.out, "31.0 - floor(log2(float(")?;
                                 self.write_expr(arg, ctx)?;
-                                write!(self.out, ") + 0.5) * {LOG2_E})))")?;
+                                write!(self.out, ") + 0.5))))")?;
                             }
                             _ => unreachable!(),
                         };

diff --git a/tests/out/glsl/math-functions.main.Vertex.glsl b/tests/out/glsl/math-functions.main.Vertex.glsl
@@ -14,11 +14,11 @@ void main() {
     vec4 g = refract(v, v, 1.0);
     int const_dot = ( + ivec2(0, 0).x * ivec2(0, 0).x + ivec2(0, 0).y * ivec2(0, 0).y);
     uint first_leading_bit_abs = uint(findMSB(uint(abs(int(0u)))));
-    int clz_a = (-1 <= 0 ? (-1 == 0 ? 32 : 0) : int(31.0 - floor(log(float(-1) + 0.5) * 1.442695)));
-    uint clz_b = (1u == 0u ? 32u : uint(31.0 - floor(log(float(1u) + 0.5) * 1.442695)));
+    int clz_a = (-1 <= 0 ? (-1 == 0 ? 32 : 0) : int(31.0 - floor(log2(float(-1) + 0.5))));
+    uint clz_b = (1u == 0u ? 32u : uint(31.0 - floor(log2(float(1u) + 0.5))));
     ivec2 _e20 = ivec2(-1);
-    ivec2 clz_c = ivec2(mix(vec2(31.0) - floor(log(vec2(_e20) + 0.5) * 1.442695), mix(vec2(0.0), vec2(32.0), equal(_e20, ivec2(0))), lessThanEqual(_e20, ivec2(0))));
+    ivec2 clz_c = ivec2(mix(vec2(31.0) - floor(log2(vec2(_e20) + 0.5)), mix(vec2(0.0), vec2(32.0), equal(_e20, ivec2(0))), lessThanEqual(_e20, ivec2(0))));
     uvec2 _e23 = uvec2(1u);
-    uvec2 clz_d = uvec2(mix(vec2(31.0) - floor(log(vec2(_e23) + 0.5) * 1.442695), vec2(32.0), lessThanEqual(_e23, uvec2(0u))));
+    uvec2 clz_d = uvec2(mix(vec2(31.0) - floor(log2(vec2(_e23) + 0.5)), vec2(32.0), lessThanEqual(_e23, uvec2(0u))));
 }