render: Implement PixelBender Operation::Select (renamed from Loop) (#14503)

render/naga-pixelbender/src/lib.rs

@@ -1388,8 +1388,44 @@ impl<'a> ShaderBuilder<'a> {
                         }
                     }
                 }
-                Operation::Loop { unknown } => {
-                    tracing::warn!("Unimplemented Loop opcode with data: {unknown:?}")
+                Operation::Select {
+                    src1,
+                    src2,
+                    dst,
+                    condition,
+                } => {
+                    let src1_expr = self.load_src_register(src1)?;
+                    let src2_expr = self.load_src_register(src2)?;
+
+                    let expr_zero: Handle<Expression> = match condition.kind {
+                        PixelBenderRegKind::Float => self.zerof32,
+                        PixelBenderRegKind::Int => self.zeroi32,
+                    };
+                    if condition.channels.len() != 1 {
+                        panic!("'Select' condition must be a scalar: {condition:?}");
+                    }
+
+                    // FIXME - `load_src_register` always gives us a vec4 - ideally, we would
+                    // have a flag to avoid this pointless splat-and-extract.
+                    let cond_expr = self.load_src_register(condition)?;
+                    let first_component = self.evaluate_expr(Expression::AccessIndex {
+                        base: cond_expr,
+                        index: 0,
+                    });
+
+                    let is_true = self.evaluate_expr(Expression::Binary {
+                        op: BinaryOperator::NotEqual,
+                        left: first_component,
+                        right: expr_zero,
+                    });
+
+                    let select_expr = self.evaluate_expr(Expression::Select {
+                        condition: is_true,
+                        accept: src1_expr,
+                        reject: src2_expr,
+                    });
+
+                    self.emit_dest_store(select_expr, dst)?;
                 }
                 Operation::Nop => {}
             }

render/src/pixel_bender.rs

@@ -199,7 +199,7 @@ pub enum Opcode {
     SampleNearest = 0x30,
     SampleLinear = 0x31,
     LoadIntOrFloat = 0x32,
-    Loop = 0x33,
+    Select = 0x33,
     If = 0x34,
     Else = 0x35,
     EndIf = 0x36,
@@ -250,8 +250,11 @@ pub enum Operation {
     },
     Else,
     EndIf,
-    Loop {
-        unknown: Box<[u8]>,
+    Select {
+        src1: PixelBenderReg,
+        src2: PixelBenderReg,
+        condition: PixelBenderReg,
+        dst: PixelBenderReg,
     },
 }
 
@@ -585,11 +588,29 @@ fn read_op<R: Read>(
                 _ => unreachable!(),
             }
         }
-        Opcode::Loop => {
-            let mut unknown = vec![0u8; 23];
-            data.read_exact(&mut unknown)?;
-            shader.operations.push(Operation::Loop {
-                unknown: unknown.into(),
+        Opcode::Select => {
+            let dst = data.read_u16::<LittleEndian>()?;
+            let mask = data.read_u8()?;
+            assert_eq!(mask & 0xF, 0);
+            let dst_reg = read_dst_reg(dst, mask >> 4)?;
+
+            let condition = read_uint24(data)?;
+            assert_eq!(data.read_u8()?, 0);
+            let condition_reg = read_src_reg(condition, 1)?;
+
+            let src1 = read_uint24(data)?;
+            assert_eq!(data.read_u8()?, 0);
+            let src_reg1 = read_src_reg(src1, 1)?;
+
+            let src2 = read_uint24(data)?;
+            assert_eq!(data.read_u8()?, 0);
+            let src_reg2 = read_src_reg(src2, 1)?;
+
+            shader.operations.push(Operation::Select {
+                condition: condition_reg,
+                src1: src_reg1,
+                src2: src_reg2,
+                dst: dst_reg,
             });
         }
         _ => {

tests/tests/swfs/avm2/pixelbender_dithering/output.txt

@@ -0,0 +1,8 @@
+Shader metadata: description Value: Ordered Dithering
+Shader parameter: matrixHeight Value: 4
+Shader parameter: matrixWidth Value: 4
+Shader metadata: name Value: OrderDithering
+Shader metadata: namespace Value: YourNamespace
+Shader input: src Value: null
+Shader metadata: vendor Value: YourVendor
+Shader metadata: version Value: 1

tests/tests/swfs/avm2/pixelbender_dithering/test.toml

@@ -0,0 +1,10 @@
+# Based on https://github.com/FlashBacks1998/Custom-Pixel-Bender-Example-Ordered-Dithering-
+# The prints were sorted to avoid relying on object iteration order
+num_ticks = 1
+
+[image_comparisons.output]
+tolerance = 1
+max_outliers = 19813
+
+[player_options]
+with_renderer = { optional = false, sample_count = 1 }