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In order to preserve padding properly for MSL, we need to use its packed_vec type for all vec3 types in storage buffers, not just struct members. This commit includes a complete rewrite of the PackedVec3 transform to achieve this. The key details are: * An internal `__packed_vec3<>` type was added, which corresponds to a `type::Vector` with an additional flag to indicate that it will be emitted as packed vector. * The `PackedVec3` transform replaces all vec3 types used in host-shareable address spaces with the internal `__packed_vec3` type. This includes vec3 types that appear as the store type of a pointer. * When used as an array element, these `__packed_vec3` types are wrapped in a struct that contains a single `__packed_vec3` member. This allows us to add an `@align()` attribute that ensures that `array<vec3<T>>` still has the correct array element stride. * When the `vec3<T>` appears as a struct member in the input program, we apply the `@align()` to that member to ensure that we do not change its offset. * Matrix types with three rows that are used in memory are replaced with an array of columns, where each column uses a `__packed_vec3` inside an aligned wrapper structure as above. * Accesses to host-shareable memory that involve any of these types invoke a "pack" or "unpack" helper function to convert them to the equivalent type that uses `__packed_vec3` or a regular `vec3` as required. * The `chromium_internal_relaxed_uniform_layout` extension is used to avoid issues where modifying a type in the uniform address space triggers stricter layout validation rules. Bug: tint:1571 Fixed: tint:1837 Change-Id: Idaf2da2f5bcb2be00c85ec657edfb614186476bb Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/121200 Reviewed-by: Ben Clayton <bclayton@google.com> Commit-Queue: James Price <jrprice@google.com> Kokoro: Kokoro <noreply+kokoro@google.com> |
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