From 030b924e2a973508abe66a6074fb135c3572c03b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jo=C3=A3o=20Capucho?= <jcapucho7@gmail.com>
Date: Mon, 11 Apr 2022 22:01:51 +0100
Subject: [PATCH] glsl-in: Add tests for constants NaN handling

---
 src/front/glsl/constants.rs | 26 +++++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

diff --git a/src/front/glsl/constants.rs b/src/front/glsl/constants.rs
index e537370858..0c7c4ed6ae 100644
--- a/src/front/glsl/constants.rs
+++ b/src/front/glsl/constants.rs
@@ -234,9 +234,7 @@ impl<'a> ConstantSolver<'a> {
                                         ScalarValue::Float(a),
                                         ScalarValue::Float(b),
                                         ScalarValue::Float(c),
-                                    ) => {
-                                        ScalarValue::Float(glsl_float_min(glsl_float_max(a, b), c))
-                                    }
+                                    ) => ScalarValue::Float(glsl_float_clamp(a, b, c)),
                                     _ => return Err(ConstantSolvingError::InvalidMathArg),
                                 },
                                 width,
@@ -599,6 +597,15 @@ fn glsl_float_min(x: f64, y: f64) -> f64 {
     }
 }
 
+/// Helper function to implement the GLSL `clamp` function for floats.
+///
+/// While Rust does provide a `f64::clamp` method, it requires a version of rust
+/// above our MSRV and it also panics if either `min` or `max` are `NaN`s which
+/// is not the behavior specified by the glsl specification.
+fn glsl_float_clamp(value: f64, min: f64, max: f64) -> f64 {
+    glsl_float_min(glsl_float_max(value, min), max)
+}
+
 #[cfg(test)]
 mod tests {
     use std::vec;
@@ -610,6 +617,19 @@ mod tests {
 
     use super::ConstantSolver;
 
+    #[test]
+    fn nan_handling() {
+        assert!(super::glsl_float_max(f64::NAN, 2.0).is_nan());
+        assert!(!super::glsl_float_max(2.0, f64::NAN).is_nan());
+
+        assert!(super::glsl_float_min(f64::NAN, 2.0).is_nan());
+        assert!(!super::glsl_float_min(2.0, f64::NAN).is_nan());
+
+        assert!(super::glsl_float_clamp(f64::NAN, 1.0, 2.0).is_nan());
+        assert!(!super::glsl_float_clamp(1.0, f64::NAN, 2.0).is_nan());
+        assert!(!super::glsl_float_clamp(1.0, 2.0, f64::NAN).is_nan());
+    }
+
     #[test]
     fn unary_op() {
         let mut types = UniqueArena::new();