Implement ddx, ddy, fwidth
#![no_std]
#![feature(register_attr, repr_simd, core_intrinsics)]
+#![cfg_attr(target_arch = "spirv", feature(asm))]
#![register_attr(spirv)]
// Our standard Clippy lints that we use in Embark projects, we opt out of a few that are not appropriate for the specific crate (yet)
#![warn(
@@ -97,6 +98,68 @@ pointer_addrspace!(incoming_ray_payload_khr, IncomingRayPayloadKHR, true);
pointer_addrspace!(shader_record_buffer_khr, ShaderRecordBufferKHR, true);
pointer_addrspace!(physical_storage_buffer, PhysicalStorageBuffer, true);
+pub trait Derivative {
+ fn ddx(self) -> Self;
+ fn ddx_fine(self) -> Self;
+ fn ddx_coarse(self) -> Self;
+ fn ddy(self) -> Self;
+ fn ddy_fine(self) -> Self;
+ fn ddy_coarse(self) -> Self;
+ fn fwidth(self) -> Self;
+ fn fwidth_fine(self) -> Self;
+ fn fwidth_coarse(self) -> Self;
+}
+
+#[cfg(target_arch = "spirv")]
+macro_rules! deriv_caps {
+ (true) => {
+ asm!("OpCapability DerivativeControl")
+ };
+ (false) => {};
+}
+
+macro_rules! deriv_fn {
+ ($name:ident, $inst:ident, $needs_caps:tt) => {
+ fn $name(self) -> Self {
+ #[cfg(not(target_arch = "spirv"))]
+ panic!(concat!(stringify!($name), " is not supported on the CPU"));
+ #[cfg(target_arch = "spirv")]
+ unsafe {
+ let o;
+ deriv_caps!($needs_caps);
+ asm!(
+ concat!("{1} = ", stringify!($inst), " typeof{0} {0}"),
+ in(reg) self,
+ out(reg) o,
+ );
+ o
+ }
+ }
+ };
+}
+macro_rules! deriv_impl {
+ ($ty:ty) => {
+ impl Derivative for $ty {
+ deriv_fn!(ddx, OpDPdx, false);
+ deriv_fn!(ddx_fine, OpDPdxFine, true);
+ deriv_fn!(ddx_coarse, OpDPdxCoarse, true);
+ deriv_fn!(ddy, OpDPdy, false);
+ deriv_fn!(ddy_fine, OpDPdyFine, true);
+ deriv_fn!(ddy_coarse, OpDPdyCoarse, true);
+ deriv_fn!(fwidth, OpFwidth, false);
+ deriv_fn!(fwidth_fine, OpFwidthFine, true);
+ deriv_fn!(fwidth_coarse, OpFwidthCoarse, true);
+ }
+ };
+}
+
+// "must be a scalar or vector of floating-point type. The component width must be 32 bits."
+deriv_impl!(f32);
+// TODO: Fix rustc to support these
+// deriv_impl!(glam::Vec2);
+// deriv_impl!(glam::Vec3);
+// deriv_impl!(glam::Vec4);
+
/// libcore requires a few external symbols to be defined:
/// <https://github.com/rust-lang/rust/blob/c2bc344eb23d8c1d18e803b3f1e631cf99926fbb/library/core/src/lib.rs#L23-L27>
/// TODO: This is copied from `compiler_builtins/mem.rs`. Can we use that one instead? The note in the above link says
