[naga/wgsl-out]: polyfill inverse function

CHANGELOG.md

@@ -84,6 +84,7 @@ By @bradwerth [#6216](https://github.com/gfx-rs/wgpu/pull/6216).
 - Support for more atomic ops in the SPIR-V frontend. By @schell in [#5824](https://github.com/gfx-rs/wgpu/pull/5824).
 - Support local `const` declarations in WGSL. By @sagudev in [#6156](https://github.com/gfx-rs/wgpu/pull/6156).
 - Implemented `const_assert` in WGSL. By @sagudev in [#6198](https://github.com/gfx-rs/wgpu/pull/6198).
+- Support polyfilling `inverse` in WGSL. By @chyyran in [#6385](https://github.com/gfx-rs/wgpu/pull/6385).
 
 #### General
 

naga/src/back/wgsl/mod.rs

@@ -4,6 +4,7 @@ Backend for [WGSL][wgsl] (WebGPU Shading Language).
 [wgsl]: https://gpuweb.github.io/gpuweb/wgsl.html
 */
 
+mod polyfill;
 mod writer;
 
 use thiserror::Error;

naga/src/back/wgsl/polyfill/inverse/inverse_2x2_f16.wgsl

@@ -0,0 +1,10 @@
+fn _naga_inverse_2x2_f16(m: mat2x2<f16>) -> mat2x2<f16> {
+    var adj: mat2x2<f16>;
+    adj[0][0] = m[1][1];
+    adj[0][1] = -m[0][1];
+    adj[1][0] = -m[1][0];
+    adj[1][1] = m[0][0];
+
+    let det: f16 = m[0][0] * m[1][1] - m[1][0] * m[0][1];
+    return adj * (1 / det);
+}

naga/src/back/wgsl/polyfill/inverse/inverse_2x2_f32.wgsl

@@ -0,0 +1,10 @@
+fn _naga_inverse_2x2_f32(m: mat2x2<f32>) -> mat2x2<f32> {
+    var adj: mat2x2<f32>;
+    adj[0][0] = m[1][1];
+    adj[0][1] = -m[0][1];
+    adj[1][0] = -m[1][0];
+    adj[1][1] = m[0][0];
+
+    let det: f32 = m[0][0] * m[1][1] - m[1][0] * m[0][1];
+    return adj * (1 / det);
+}

naga/src/back/wgsl/polyfill/inverse/inverse_3x3_f16.wgsl

@@ -0,0 +1,19 @@
+fn _naga_inverse_3x3_f16(m: mat3x3<f16>) -> mat3x3<f16> {
+    var adj: mat3x3<f16>;
+
+    adj[0][0] =   (m[1][1] * m[2][2] - m[2][1] * m[1][2]);
+    adj[1][0] = - (m[1][0] * m[2][2] - m[2][0] * m[1][2]);
+    adj[2][0] =   (m[1][0] * m[2][1] - m[2][0] * m[1][1]);
+    adj[0][1] = - (m[0][1] * m[2][2] - m[2][1] * m[0][2]);
+    adj[1][1] =   (m[0][0] * m[2][2] - m[2][0] * m[0][2]);
+    adj[2][1] = - (m[0][0] * m[2][1] - m[2][0] * m[0][1]);
+    adj[0][2] =   (m[0][1] * m[1][2] - m[1][1] * m[0][2]);
+    adj[1][2] = - (m[0][0] * m[1][2] - m[1][0] * m[0][2]);
+    adj[2][2] =   (m[0][0] * m[1][1] - m[1][0] * m[0][1]);
+
+    let det: f16 = (m[0][0] * (m[1][1] * m[2][2] - m[1][2] * m[2][1])
+    		- m[0][1] * (m[1][0] * m[2][2] - m[1][2] * m[2][0])
+    		+ m[0][2] * (m[1][0] * m[2][1] - m[1][1] * m[2][0]));
+
+    return adj * (1 / det);
+}

naga/src/back/wgsl/polyfill/inverse/inverse_3x3_f32.wgsl

@@ -0,0 +1,19 @@
+fn _naga_inverse_3x3_f32(m: mat3x3<f32>) -> mat3x3<f32> {
+    var adj: mat3x3<f32>;
+
+    adj[0][0] =   (m[1][1] * m[2][2] - m[2][1] * m[1][2]);
+    adj[1][0] = - (m[1][0] * m[2][2] - m[2][0] * m[1][2]);
+    adj[2][0] =   (m[1][0] * m[2][1] - m[2][0] * m[1][1]);
+    adj[0][1] = - (m[0][1] * m[2][2] - m[2][1] * m[0][2]);
+    adj[1][1] =   (m[0][0] * m[2][2] - m[2][0] * m[0][2]);
+    adj[2][1] = - (m[0][0] * m[2][1] - m[2][0] * m[0][1]);
+    adj[0][2] =   (m[0][1] * m[1][2] - m[1][1] * m[0][2]);
+    adj[1][2] = - (m[0][0] * m[1][2] - m[1][0] * m[0][2]);
+    adj[2][2] =   (m[0][0] * m[1][1] - m[1][0] * m[0][1]);
+
+    let det: f32 = (m[0][0] * (m[1][1] * m[2][2] - m[1][2] * m[2][1])
+    		- m[0][1] * (m[1][0] * m[2][2] - m[1][2] * m[2][0])
+    		+ m[0][2] * (m[1][0] * m[2][1] - m[1][1] * m[2][0]));
+
+    return adj * (1 / det);
+}

naga/src/back/wgsl/polyfill/inverse/inverse_4x4_f16.wgsl

@@ -0,0 +1,43 @@
+fn _naga_inverse_4x4_f16(m: mat4x4<f16>) -> mat4x4<f16> {
+   let sub_factor00: f16 = m[2][2] * m[3][3] - m[3][2] * m[2][3];
+   let sub_factor01: f16 = m[2][1] * m[3][3] - m[3][1] * m[2][3];
+   let sub_factor02: f16 = m[2][1] * m[3][2] - m[3][1] * m[2][2];
+   let sub_factor03: f16 = m[2][0] * m[3][3] - m[3][0] * m[2][3];
+   let sub_factor04: f16 = m[2][0] * m[3][2] - m[3][0] * m[2][2];
+   let sub_factor05: f16 = m[2][0] * m[3][1] - m[3][0] * m[2][1];
+   let sub_factor06: f16 = m[1][2] * m[3][3] - m[3][2] * m[1][3];
+   let sub_factor07: f16 = m[1][1] * m[3][3] - m[3][1] * m[1][3];
+   let sub_factor08: f16 = m[1][1] * m[3][2] - m[3][1] * m[1][2];
+   let sub_factor09: f16 = m[1][0] * m[3][3] - m[3][0] * m[1][3];
+   let sub_factor10: f16 = m[1][0] * m[3][2] - m[3][0] * m[1][2];
+   let sub_factor11: f16 = m[1][1] * m[3][3] - m[3][1] * m[1][3];
+   let sub_factor12: f16 = m[1][0] * m[3][1] - m[3][0] * m[1][1];
+   let sub_factor13: f16 = m[1][2] * m[2][3] - m[2][2] * m[1][3];
+   let sub_factor14: f16 = m[1][1] * m[2][3] - m[2][1] * m[1][3];
+   let sub_factor15: f16 = m[1][1] * m[2][2] - m[2][1] * m[1][2];
+   let sub_factor16: f16 = m[1][0] * m[2][3] - m[2][0] * m[1][3];
+   let sub_factor17: f16 = m[1][0] * m[2][2] - m[2][0] * m[1][2];
+   let sub_factor18: f16 = m[1][0] * m[2][1] - m[2][0] * m[1][1];
+
+   var adj: mat4x4<f16>;
+   adj[0][0] =   (m[1][1] * sub_factor00 - m[1][2] * sub_factor01 + m[1][3] * sub_factor02);
+   adj[1][0] = - (m[1][0] * sub_factor00 - m[1][2] * sub_factor03 + m[1][3] * sub_factor04);
+   adj[2][0] =   (m[1][0] * sub_factor01 - m[1][1] * sub_factor03 + m[1][3] * sub_factor05);
+   adj[3][0] = - (m[1][0] * sub_factor02 - m[1][1] * sub_factor04 + m[1][2] * sub_factor05);
+   adj[0][1] = - (m[0][1] * sub_factor00 - m[0][2] * sub_factor01 + m[0][3] * sub_factor02);
+   adj[1][1] =   (m[0][0] * sub_factor00 - m[0][2] * sub_factor03 + m[0][3] * sub_factor04);
+   adj[2][1] = - (m[0][0] * sub_factor01 - m[0][1] * sub_factor03 + m[0][3] * sub_factor05);
+   adj[3][1] =   (m[0][0] * sub_factor02 - m[0][1] * sub_factor04 + m[0][2] * sub_factor05);
+   adj[0][2] =   (m[0][1] * sub_factor06 - m[0][2] * sub_factor07 + m[0][3] * sub_factor08);
+   adj[1][2] = - (m[0][0] * sub_factor06 - m[0][2] * sub_factor09 + m[0][3] * sub_factor10);
+   adj[2][2] =   (m[0][0] * sub_factor11 - m[0][1] * sub_factor09 + m[0][3] * sub_factor12);
+   adj[3][2] = - (m[0][0] * sub_factor08 - m[0][1] * sub_factor10 + m[0][2] * sub_factor12);
+   adj[0][3] = - (m[0][1] * sub_factor13 - m[0][2] * sub_factor14 + m[0][3] * sub_factor15);
+   adj[1][3] =   (m[0][0] * sub_factor13 - m[0][2] * sub_factor16 + m[0][3] * sub_factor17);
+   adj[2][3] = - (m[0][0] * sub_factor14 - m[0][1] * sub_factor16 + m[0][3] * sub_factor18);
+   adj[3][3] =   (m[0][0] * sub_factor15 - m[0][1] * sub_factor17 + m[0][2] * sub_factor18);
+
+   let det = (m[0][0] * adj[0][0] + m[0][1] * adj[1][0] + m[0][2] * adj[2][0] + m[0][3] * adj[3][0]);
+
+   return adj * (1 / det);
+}

naga/src/back/wgsl/polyfill/inverse/inverse_4x4_f32.wgsl

@@ -0,0 +1,43 @@
+fn _naga_inverse_4x4_f32(m: mat4x4<f32>) -> mat4x4<f32> {
+   let sub_factor00: f32 = m[2][2] * m[3][3] - m[3][2] * m[2][3];
+   let sub_factor01: f32 = m[2][1] * m[3][3] - m[3][1] * m[2][3];
+   let sub_factor02: f32 = m[2][1] * m[3][2] - m[3][1] * m[2][2];
+   let sub_factor03: f32 = m[2][0] * m[3][3] - m[3][0] * m[2][3];
+   let sub_factor04: f32 = m[2][0] * m[3][2] - m[3][0] * m[2][2];
+   let sub_factor05: f32 = m[2][0] * m[3][1] - m[3][0] * m[2][1];
+   let sub_factor06: f32 = m[1][2] * m[3][3] - m[3][2] * m[1][3];
+   let sub_factor07: f32 = m[1][1] * m[3][3] - m[3][1] * m[1][3];
+   let sub_factor08: f32 = m[1][1] * m[3][2] - m[3][1] * m[1][2];
+   let sub_factor09: f32 = m[1][0] * m[3][3] - m[3][0] * m[1][3];
+   let sub_factor10: f32 = m[1][0] * m[3][2] - m[3][0] * m[1][2];
+   let sub_factor11: f32 = m[1][1] * m[3][3] - m[3][1] * m[1][3];
+   let sub_factor12: f32 = m[1][0] * m[3][1] - m[3][0] * m[1][1];
+   let sub_factor13: f32 = m[1][2] * m[2][3] - m[2][2] * m[1][3];
+   let sub_factor14: f32 = m[1][1] * m[2][3] - m[2][1] * m[1][3];
+   let sub_factor15: f32 = m[1][1] * m[2][2] - m[2][1] * m[1][2];
+   let sub_factor16: f32 = m[1][0] * m[2][3] - m[2][0] * m[1][3];
+   let sub_factor17: f32 = m[1][0] * m[2][2] - m[2][0] * m[1][2];
+   let sub_factor18: f32 = m[1][0] * m[2][1] - m[2][0] * m[1][1];
+
+   var adj: mat4x4<f32>;
+   adj[0][0] =   (m[1][1] * sub_factor00 - m[1][2] * sub_factor01 + m[1][3] * sub_factor02);
+   adj[1][0] = - (m[1][0] * sub_factor00 - m[1][2] * sub_factor03 + m[1][3] * sub_factor04);
+   adj[2][0] =   (m[1][0] * sub_factor01 - m[1][1] * sub_factor03 + m[1][3] * sub_factor05);
+   adj[3][0] = - (m[1][0] * sub_factor02 - m[1][1] * sub_factor04 + m[1][2] * sub_factor05);
+   adj[0][1] = - (m[0][1] * sub_factor00 - m[0][2] * sub_factor01 + m[0][3] * sub_factor02);
+   adj[1][1] =   (m[0][0] * sub_factor00 - m[0][2] * sub_factor03 + m[0][3] * sub_factor04);
+   adj[2][1] = - (m[0][0] * sub_factor01 - m[0][1] * sub_factor03 + m[0][3] * sub_factor05);
+   adj[3][1] =   (m[0][0] * sub_factor02 - m[0][1] * sub_factor04 + m[0][2] * sub_factor05);
+   adj[0][2] =   (m[0][1] * sub_factor06 - m[0][2] * sub_factor07 + m[0][3] * sub_factor08);
+   adj[1][2] = - (m[0][0] * sub_factor06 - m[0][2] * sub_factor09 + m[0][3] * sub_factor10);
+   adj[2][2] =   (m[0][0] * sub_factor11 - m[0][1] * sub_factor09 + m[0][3] * sub_factor12);
+   adj[3][2] = - (m[0][0] * sub_factor08 - m[0][1] * sub_factor10 + m[0][2] * sub_factor12);
+   adj[0][3] = - (m[0][1] * sub_factor13 - m[0][2] * sub_factor14 + m[0][3] * sub_factor15);
+   adj[1][3] =   (m[0][0] * sub_factor13 - m[0][2] * sub_factor16 + m[0][3] * sub_factor17);
+   adj[2][3] = - (m[0][0] * sub_factor14 - m[0][1] * sub_factor16 + m[0][3] * sub_factor18);
+   adj[3][3] =   (m[0][0] * sub_factor15 - m[0][1] * sub_factor17 + m[0][2] * sub_factor18);
+
+   let det = (m[0][0] * adj[0][0] + m[0][1] * adj[1][0] + m[0][2] * adj[2][0] + m[0][3] * adj[3][0]);
+
+   return adj * (1 / det);
+}

naga/src/back/wgsl/polyfill/mod.rs

@@ -0,0 +1,66 @@
+use crate::{ScalarKind, TypeInner, VectorSize};
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub struct InversePolyfill {
+    pub fun_name: &'static str,
+    pub source: &'static str,
+}
+
+impl InversePolyfill {
+    pub fn find_overload(ty: &TypeInner) -> Option<InversePolyfill> {
+        let &TypeInner::Matrix {
+            columns,
+            rows,
+            scalar,
+        } = ty
+        else {
+            return None;
+        };
+
+        if columns != rows || scalar.kind != ScalarKind::Float {
+            return None;
+        };
+
+        Self::polyfill_overload(columns, scalar.width)
+    }
+
+    const fn polyfill_overload(
+        dimension: VectorSize,
+        width: crate::Bytes,
+    ) -> Option<InversePolyfill> {
+        const INVERSE_2X2_F32: &str = include_str!("inverse/inverse_2x2_f32.wgsl");
+        const INVERSE_3X3_F32: &str = include_str!("inverse/inverse_3x3_f32.wgsl");
+        const INVERSE_4X4_F32: &str = include_str!("inverse/inverse_4x4_f32.wgsl");
+        const INVERSE_2X2_F16: &str = include_str!("inverse/inverse_2x2_f16.wgsl");
+        const INVERSE_3X3_F16: &str = include_str!("inverse/inverse_3x3_f16.wgsl");
+        const INVERSE_4X4_F16: &str = include_str!("inverse/inverse_4x4_f16.wgsl");
+
+        match (dimension, width) {
+            (VectorSize::Bi, 4) => Some(InversePolyfill {
+                fun_name: "_naga_inverse_2x2_f32",
+                source: INVERSE_2X2_F32,
+            }),
+            (VectorSize::Tri, 4) => Some(InversePolyfill {
+                fun_name: "_naga_inverse_3x3_f32",
+                source: INVERSE_3X3_F32,
+            }),
+            (VectorSize::Quad, 4) => Some(InversePolyfill {
+                fun_name: "_naga_inverse_4x4_f32",
+                source: INVERSE_4X4_F32,
+            }),
+            (VectorSize::Bi, 2) => Some(InversePolyfill {
+                fun_name: "_naga_inverse_2x2_f16",
+                source: INVERSE_2X2_F16,
+            }),
+            (VectorSize::Tri, 2) => Some(InversePolyfill {
+                fun_name: "_naga_inverse_3x3_f16",
+                source: INVERSE_3X3_F16,
+            }),
+            (VectorSize::Quad, 2) => Some(InversePolyfill {
+                fun_name: "_naga_inverse_4x4_f16",
+                source: INVERSE_4X4_F16,
+            }),
+            _ => None,
+        }
+    }
+}

naga/src/back/wgsl/writer.rs

@@ -1,4 +1,5 @@
 use super::Error;
+use crate::back::wgsl::polyfill::InversePolyfill;
 use crate::{
     back::{self, Baked},
     proc::{self, ExpressionKindTracker, NameKey},
@@ -68,6 +69,7 @@ pub struct Writer<W> {
     namer: proc::Namer,
     named_expressions: crate::NamedExpressions,
     ep_results: Vec<(ShaderStage, Handle<crate::Type>)>,
+    required_polyfills: crate::FastIndexSet<InversePolyfill>,
 }
 
 impl<W: Write> Writer<W> {
@@ -79,6 +81,7 @@ impl<W: Write> Writer<W> {
             namer: proc::Namer::default(),
             named_expressions: crate::NamedExpressions::default(),
             ep_results: vec![],
+            required_polyfills: crate::FastIndexSet::default(),
         }
     }
 
@@ -90,11 +93,12 @@ impl<W: Write> Writer<W> {
             // an identifier must not start with two underscore
             &[],
             &[],
-            &["__"],
+            &["__", "_naga"],
             &mut self.names,
         );
         self.named_expressions.clear();
         self.ep_results.clear();
+        self.required_polyfills.clear();
     }
 
     fn is_builtin_wgsl_struct(&self, module: &Module, handle: Handle<crate::Type>) -> bool {
@@ -203,6 +207,13 @@ impl<W: Write> Writer<W> {
             }
         }
 
+        // Write any polyfills that were required.
+        for polyfill in &self.required_polyfills {
+            writeln!(self.out)?;
+            write!(self.out, "{}", polyfill.source)?;
+            writeln!(self.out)?;
+        }
+
         Ok(())
     }
 
@@ -1653,6 +1664,7 @@ impl<W: Write> Writer<W> {
 
                 enum Function {
                     Regular(&'static str),
+                    InversePolyfill(InversePolyfill),
                 }
 
                 let function = match fun {
@@ -1736,9 +1748,16 @@ impl<W: Write> Writer<W> {
                     Mf::Unpack2x16float => Function::Regular("unpack2x16float"),
                     Mf::Unpack4xI8 => Function::Regular("unpack4xI8"),
                     Mf::Unpack4xU8 => Function::Regular("unpack4xU8"),
-                    Mf::Inverse | Mf::Outer => {
-                        return Err(Error::UnsupportedMathFunction(fun));
+                    Mf::Inverse => {
+                        let typ = func_ctx.resolve_type(arg, &module.types);
+
+                        let Some(overload) = InversePolyfill::find_overload(typ) else {
+                            return Err(Error::UnsupportedMathFunction(fun));
+                        };
+
+                        Function::InversePolyfill(overload)
                     }
+                    Mf::Outer => return Err(Error::UnsupportedMathFunction(fun)),
                 };
 
                 match function {
@@ -1751,6 +1770,12 @@ impl<W: Write> Writer<W> {
                         }
                         write!(self.out, ")")?
                     }
+                    Function::InversePolyfill(inverse) => {
+                        write!(self.out, "{}(", inverse.fun_name)?;
+                        self.write_expr(module, arg, func_ctx)?;
+                        write!(self.out, ")")?;
+                        self.required_polyfills.insert(inverse);
+                    }
                 }
             }
 

naga/tests/in/glsl/inverse-polyfill.frag

@@ -0,0 +1,17 @@
+#version 450
+
+void main() {
+    vec4 a4 = vec4(1.0);
+    vec4 b4 = vec4(2.0);
+    mat4 m4 = mat4(a4, b4, a4, b4);
+
+    vec3 a3 = vec3(1.0);
+    vec3 b3 = vec3(2.0);
+    mat3 m3 = mat3(a3, b3, a3);
+
+    mat2 m2 = mat2(1.0, 2.0, 3.0, 4.0);
+
+    mat4 m4_inverse = inverse(m4);
+    mat3 m3_inverse = inverse(m3);
+    mat2 m2_inverse = inverse(m2);
+}