Add FMA feature to glsl backend

- I think this is right. Just iterate all known expressions in all functions and entry points to locate any `fma` function call. Should not need to walk the statement DAG.
gfx-rs · Dec 7, 2021 · 5cec686 · 5cec686
1 parent beddc71
commit 5cec686
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Showing 2 changed files with 30 additions and 2 deletions.
diff --git a/src/back/glsl/features.rs b/src/back/glsl/features.rs
@@ -1,7 +1,7 @@
 use super::{BackendResult, Error, Version, Writer};
 use crate::{
-    Binding, Bytes, Handle, ImageClass, ImageDimension, Interpolation, Sampling, ScalarKind,
-    ShaderStage, StorageClass, StorageFormat, Type, TypeInner,
+    Binding, Bytes, Expression, Handle, ImageClass, ImageDimension, Interpolation, MathFunction,
+    Sampling, ScalarKind, ShaderStage, StorageClass, StorageFormat, Type, TypeInner,
 };
 use std::fmt::Write;
 
@@ -33,6 +33,8 @@ bitflags::bitflags! {
         /// Arrays with a dynamic length
         const DYNAMIC_ARRAY_SIZE = 1 << 16;
         const MULTI_VIEW = 1 << 17;
+        /// Adds support for fused multiply-add
+        const FMA = 1 << 18;
     }
 }
 
@@ -98,6 +100,7 @@ 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);
 
         // Return an error if there are missing features
         if missing.is_empty() {
@@ -201,6 +204,11 @@ impl FeaturesManager {
             writeln!(out, "#extension GL_EXT_multiview : require")?;
         }
 
+        if self.0.contains(Features::FMA) && version.is_es() {
+            // https://www.khronos.org/registry/OpenGL/extensions/EXT/EXT_gpu_shader5.txt
+            writeln!(out, "#extension GL_EXT_gpu_shader5 : require")?;
+        }
+
         Ok(())
     }
 }
@@ -347,6 +355,25 @@ impl<'a, W> Writer<'a, W> {
             }
         }
 
+        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);
+        }
+
         self.features.check_availability(self.options.version)
     }
 

diff --git a/tests/out/glsl/functions.main.Compute.glsl b/tests/out/glsl/functions.main.Compute.glsl
@@ -1,4 +1,5 @@
 #version 310 es
+#extension GL_EXT_gpu_shader5 : require
 
 precision highp float;
 precision highp int;