glsl-out: Fix feature search in expressions

The fma wasn't being searched in case it wasn't supported which is the
opposite of what we want since if it's used we want to error if it isn't
supported.

It was also searching in all entry points instead of only in the current
one.

All samples queries need the ARB_shader_texture_image_samples extension
so we need to check if any samples queries are made and if so request
the extension.

src/back/glsl/features.rs

@@ -36,6 +36,8 @@ bitflags::bitflags! {
         const MULTI_VIEW = 1 << 17;
         /// Fused multiply-add.
         const FMA = 1 << 18;
+        /// Texture samples query
+        const TEXTURE_SAMPLES = 1 << 19;
     }
 }
 
@@ -101,7 +103,10 @@ impl FeaturesManager {
         check_feature!(SAMPLE_VARIABLES, 400, 300);
         check_feature!(DYNAMIC_ARRAY_SIZE, 430, 310);
         check_feature!(MULTI_VIEW, 140, 310);
-        check_feature!(FMA, 400, 310);
+        // Only available on glsl core, this means that opengl es can't query the number
+        // of samples in a image and neither do bound checks on the sample argument
+        // of texelFecth
+        check_feature!(TEXTURE_SAMPLES, 150);
 
         // Return an error if there are missing features
         if missing.is_empty() {
@@ -210,6 +215,14 @@ impl FeaturesManager {
             writeln!(out, "#extension GL_EXT_gpu_shader5 : require")?;
         }
 
+        if self.0.contains(Features::TEXTURE_SAMPLES) {
+            // https://www.khronos.org/registry/OpenGL/extensions/ARB/ARB_shader_texture_image_samples.txt
+            writeln!(
+                out,
+                "#extension GL_ARB_shader_texture_image_samples : require"
+            )?;
+        }
+
         Ok(())
     }
 }
@@ -363,24 +376,26 @@ impl<'a, W> Writer<'a, W> {
             }
         }
 
-        if self.options.version.supports_fma_function() {
-            let has_fma = self
-                .module
-                .functions
-                .iter()
-                .flat_map(|(_, f)| f.expressions.iter())
-                .chain(
-                    self.module
-                        .entry_points
-                        .iter()
-                        .flat_map(|e| e.function.expressions.iter()),
-                )
-                .any(|(_, e)| match *e {
-                    Expression::Math { fun, .. } if fun == MathFunction::Fma => true,
-                    _ => false,
-                });
-            if has_fma {
-                self.features.request(Features::FMA);
+        // Loop trough all expressions in both functions and entry points
+        // to check for needed features
+        for (_, expr) in self
+            .module
+            .functions
+            .iter()
+            .flat_map(|(_, f)| f.expressions.iter())
+            .chain(self.entry_point.function.expressions.iter())
+        {
+            match *expr {
+                // Check for fused multiply add use
+                Expression::Math { fun, .. } if fun == MathFunction::Fma => {
+                    self.features.request(Features::FMA)
+                }
+                // Check for samples query
+                Expression::ImageQuery {
+                    query: crate::ImageQuery::NumSamples,
+                    ..
+                } => self.features.request(Features::TEXTURE_SAMPLES),
+                _ => {}
             }
         }
 

src/back/glsl/mod.rs

@@ -2433,7 +2433,6 @@ impl<'a, W: Write> Writer<'a, W> {
                         }
                     }
                     crate::ImageQuery::NumSamples => {
-                        // assumes ARB_shader_texture_image_samples
                         let fun_name = match class {
                             ImageClass::Sampled { .. } | ImageClass::Depth { .. } => {
                                 "textureSamples"

tests/out/glsl/functions-webgl.main.Vertex.glsl

@@ -1,4 +1,5 @@
 #version 300 es
+#extension GL_EXT_gpu_shader5 : require
 
 precision highp float;
 precision highp int;