hlsl: Fix mat3 stores (#1467)

src/back/hlsl/storage.rs

@@ -129,7 +129,6 @@ impl<W: fmt::Write> super::Writer<'_, W> {
  crate::VectorSize::Tri => 4,
  columns => columns as u32,
  };
-
  let row_stride = width as u32 * padded_columns;
  let iter = (0..rows as u32).map(|i| {
  let ty_inner = crate::TypeInner::Vector {
@@ -267,8 +266,15 @@ impl<W: fmt::Write> super::Writer<'_, W> {
  )?;
  self.write_store_value(module, &value, func_ctx)?;
  writeln!(self.out, ";")?;
+
+ // Note: Matrices containing vec3s, due to padding, act like they contain vec4s.
+ let padded_columns = match columns {
+ crate::VectorSize::Tri => 4,
+ columns => columns as u32,
+ };
+ let row_stride = width as u32 * padded_columns;
+
  // then iterate the stores
- let row_stride = width as u32 * columns as u32;
  for i in 0..rows as u32 {
  self.temp_access_chain
  .push(SubAccess::Offset(i * row_stride));