glsl-in: Fix using swizzle as out arguments (#1632)

This worked at one point but because of some changes to the IR it was
temporarily broken.

src/front/glsl/functions.rs

@@ -756,8 +756,6 @@ impl Parser {
  // If the argument is to be passed as a pointer but the type of the
  // expression returns a vector it must mean that it was for example
  // swizzled and it must be spilled into a local before calling
- // TODO: this part doesn't work because of #1385 once that's sorted out
- // revisit this part.
  TypeInner::Vector { size, kind, width } => (
  self.module.types.insert(
  Type {
@@ -829,7 +827,40 @@ impl Parser {
  arguments.push(temp_expr);
  // Register the temporary local to be written back to it's original
  // place after the function call
- proxy_writes.push((handle, temp_expr));
+ if let Expression::Swizzle {
+ size,
+ mut vector,
+ pattern,
+ } = ctx.expressions[value]
+ {
+ if let Expression::Load { pointer } = ctx.expressions[vector] {
+ vector = pointer;
+ }
+
+ for (i, component) in pattern.iter().take(size as usize).enumerate() {
+ let original = ctx.add_expression(
+ Expression::AccessIndex {
+ base: vector,
+ index: *component as u32,
+ },
+ Span::default(),
+ body,
+ );
+
+ let temp = ctx.add_expression(
+ Expression::AccessIndex {
+ base: temp_expr,
+ index: i as u32,
+ },
+ Span::default(),
+ body,
+ );
+
+ proxy_writes.push((original, temp));
+ }
+ } else {
+ proxy_writes.push((handle, temp_expr));
+ }
  continue;
  }
 

tests/in/glsl/swizzle_write.frag

@@ -1,9 +1,11 @@
 #version 450
 
+void foo(inout vec2 p) {}
 
 void main() {
  vec3 x = vec3(2.0);
  x.zxy.xy = vec2(3.0, 4.0);
  x.rg *= 5.0;
  x.zy++;
+ foo(x.xz);
 }

tests/out/wgsl/swizzle_write-frag.wgsl

@@ -1,5 +1,10 @@
+fn foo(p: ptr<function, vec2<f32>>) {
+ return;
+}
+
 fn main_1() {
  var x: vec3<f32> = vec3<f32>(2.0, 2.0, 2.0);
+ var local: vec2<f32>;
 
  let _e3 = x;
  let _e8 = vec2<f32>(3.0, 4.0);
@@ -14,6 +19,14 @@ fn main_1() {
  let _e27 = (_e23.zy + vec2<f32>(1.0));
  x.z = _e27.x;
  x.y = _e27.y;
+ let _e32 = x;
+ let _e34 = x;
+ local = _e34.xz;
+ foo((&local));
+ let _e41 = local.x;
+ x.x = _e41;
+ let _e42 = local.y;
+ x.z = _e42;
  return;
 }