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Use 3 bits of PipelineKey to store MSAA sample count (#5826)
Sample count always power of two. Thus, it is enough to store `log2(sample_count)`. This can be implemented using [u32::trailing_zeros](https://doc.rust-lang.org/stable/std/primitive.u32.html#method.trailing_zeros). Then we can restore sample count with the `1 << stored`. You get 3 bits instead of 6 and up to 128x MSAA. This is more than is supported by any common hardware. Full table of possible variations: ``` original MSAA sample count stored loaded * 00000000000000000000000000000000 -> 000 -> 00000001 1 00000000000000000000000000000001 -> 000 -> 00000001 1 00000000000000000000000000000010 -> 001 -> 00000010 2 00000000000000000000000000000100 -> 010 -> 00000100 4 00000000000000000000000000001000 -> 011 -> 00001000 8 00000000000000000000000000010000 -> 100 -> 00010000 16 00000000000000000000000000100000 -> 101 -> 00100000 32 00000000000000000000000001000000 -> 110 -> 01000000 64 00000000000000000000000010000000 -> 111 -> 10000000 128 * 00000000000000000000000100000000 -> 000 -> 00000001 256 * 00000000000000000000001000000000 -> 001 -> 00000010 512 * 00000000000000000000010000000000 -> 010 -> 00000100 1024 * 00000000000000000000100000000000 -> 011 -> 00001000 2048 * 00000000000000000001000000000000 -> 100 -> 00010000 4096 * 00000000000000000010000000000000 -> 101 -> 00100000 8192 * 00000000000000000100000000000000 -> 110 -> 01000000 16384 * 00000000000000001000000000000000 -> 111 -> 10000000 32768 * 00000000000000010000000000000000 -> 000 -> 00000001 65536 * 00000000000000100000000000000000 -> 001 -> 00000010 131072 * 00000000000001000000000000000000 -> 010 -> 00000100 262144 * 00000000000010000000000000000000 -> 011 -> 00001000 524288 * 00000000000100000000000000000000 -> 100 -> 00010000 1048576 * 00000000001000000000000000000000 -> 101 -> 00100000 2097152 * 00000000010000000000000000000000 -> 110 -> 01000000 4194304 * 00000000100000000000000000000000 -> 111 -> 10000000 8388608 * 00000001000000000000000000000000 -> 000 -> 00000001 16777216 * 00000010000000000000000000000000 -> 001 -> 00000010 33554432 * 00000100000000000000000000000000 -> 010 -> 00000100 67108864 * 00001000000000000000000000000000 -> 011 -> 00001000 134217728 * 00010000000000000000000000000000 -> 100 -> 00010000 268435456 * 00100000000000000000000000000000 -> 101 -> 00100000 536870912 * 01000000000000000000000000000000 -> 110 -> 01000000 1073741824 * 10000000000000000000000000000000 -> 111 -> 10000000 2147483648 ```
This commit is contained in:
Lain-dono
parent
9dd5b5354f
commit
24e5e10cd4
3 changed files with 29 additions and 26 deletions
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@ -500,35 +500,36 @@ impl MeshPipeline {
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bitflags::bitflags! {
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#[repr(transparent)]
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// NOTE: Apparently quadro drivers support up to 64x MSAA.
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/// MSAA uses the highest 6 bits for the MSAA sample count - 1 to support up to 64x MSAA.
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/// MSAA uses the highest 3 bits for the MSAA log2(sample count) to support up to 128x MSAA.
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pub struct MeshPipelineKey: u32 {
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const NONE = 0;
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const TRANSPARENT_MAIN_PASS = (1 << 0);
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const MSAA_RESERVED_BITS = MeshPipelineKey::MSAA_MASK_BITS << MeshPipelineKey::MSAA_SHIFT_BITS;
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const PRIMITIVE_TOPOLOGY_RESERVED_BITS = MeshPipelineKey::PRIMITIVE_TOPOLOGY_MASK_BITS << MeshPipelineKey::PRIMITIVE_TOPOLOGY_SHIFT_BITS;
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const MSAA_RESERVED_BITS = Self::MSAA_MASK_BITS << Self::MSAA_SHIFT_BITS;
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const PRIMITIVE_TOPOLOGY_RESERVED_BITS = Self::PRIMITIVE_TOPOLOGY_MASK_BITS << Self::PRIMITIVE_TOPOLOGY_SHIFT_BITS;
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}
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}
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impl MeshPipelineKey {
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const MSAA_MASK_BITS: u32 = 0b111111;
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const MSAA_SHIFT_BITS: u32 = 32 - 6;
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const MSAA_MASK_BITS: u32 = 0b111;
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const MSAA_SHIFT_BITS: u32 = 32 - Self::MSAA_MASK_BITS.count_ones();
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const PRIMITIVE_TOPOLOGY_MASK_BITS: u32 = 0b111;
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const PRIMITIVE_TOPOLOGY_SHIFT_BITS: u32 = Self::MSAA_SHIFT_BITS - 3;
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pub fn from_msaa_samples(msaa_samples: u32) -> Self {
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let msaa_bits = ((msaa_samples - 1) & Self::MSAA_MASK_BITS) << Self::MSAA_SHIFT_BITS;
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MeshPipelineKey::from_bits(msaa_bits).unwrap()
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let msaa_bits =
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(msaa_samples.trailing_zeros() & Self::MSAA_MASK_BITS) << Self::MSAA_SHIFT_BITS;
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Self::from_bits(msaa_bits).unwrap()
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}
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pub fn msaa_samples(&self) -> u32 {
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((self.bits >> Self::MSAA_SHIFT_BITS) & Self::MSAA_MASK_BITS) + 1
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1 << ((self.bits >> Self::MSAA_SHIFT_BITS) & Self::MSAA_MASK_BITS)
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}
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pub fn from_primitive_topology(primitive_topology: PrimitiveTopology) -> Self {
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let primitive_topology_bits = ((primitive_topology as u32)
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& Self::PRIMITIVE_TOPOLOGY_MASK_BITS)
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<< Self::PRIMITIVE_TOPOLOGY_SHIFT_BITS;
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MeshPipelineKey::from_bits(primitive_topology_bits).unwrap()
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Self::from_bits(primitive_topology_bits).unwrap()
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}
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pub fn primitive_topology(&self) -> PrimitiveTopology {
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@ -923,7 +924,7 @@ mod tests {
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use super::MeshPipelineKey;
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#[test]
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fn mesh_key_msaa_samples() {
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for i in 1..=64 {
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for i in [1, 2, 4, 8, 16, 32, 64, 128] {
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assert_eq!(MeshPipelineKey::from_msaa_samples(i).msaa_samples(), i);
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}
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}
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@ -269,35 +269,36 @@ impl Mesh2dPipeline {
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bitflags::bitflags! {
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#[repr(transparent)]
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// NOTE: Apparently quadro drivers support up to 64x MSAA.
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// MSAA uses the highest 6 bits for the MSAA sample count - 1 to support up to 64x MSAA.
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// MSAA uses the highest 3 bits for the MSAA log2(sample count) to support up to 128x MSAA.
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// FIXME: make normals optional?
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pub struct Mesh2dPipelineKey: u32 {
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const NONE = 0;
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const MSAA_RESERVED_BITS = Mesh2dPipelineKey::MSAA_MASK_BITS << Mesh2dPipelineKey::MSAA_SHIFT_BITS;
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const PRIMITIVE_TOPOLOGY_RESERVED_BITS = Mesh2dPipelineKey::PRIMITIVE_TOPOLOGY_MASK_BITS << Mesh2dPipelineKey::PRIMITIVE_TOPOLOGY_SHIFT_BITS;
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const MSAA_RESERVED_BITS = Self::MSAA_MASK_BITS << Self::MSAA_SHIFT_BITS;
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const PRIMITIVE_TOPOLOGY_RESERVED_BITS = Self::PRIMITIVE_TOPOLOGY_MASK_BITS << Self::PRIMITIVE_TOPOLOGY_SHIFT_BITS;
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}
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}
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impl Mesh2dPipelineKey {
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const MSAA_MASK_BITS: u32 = 0b111111;
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const MSAA_SHIFT_BITS: u32 = 32 - 6;
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const MSAA_MASK_BITS: u32 = 0b111;
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const MSAA_SHIFT_BITS: u32 = 32 - Self::MSAA_MASK_BITS.count_ones();
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const PRIMITIVE_TOPOLOGY_MASK_BITS: u32 = 0b111;
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const PRIMITIVE_TOPOLOGY_SHIFT_BITS: u32 = Self::MSAA_SHIFT_BITS - 3;
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pub fn from_msaa_samples(msaa_samples: u32) -> Self {
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let msaa_bits = ((msaa_samples - 1) & Self::MSAA_MASK_BITS) << Self::MSAA_SHIFT_BITS;
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Mesh2dPipelineKey::from_bits(msaa_bits).unwrap()
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let msaa_bits =
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(msaa_samples.trailing_zeros() & Self::MSAA_MASK_BITS) << Self::MSAA_SHIFT_BITS;
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Self::from_bits(msaa_bits).unwrap()
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}
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pub fn msaa_samples(&self) -> u32 {
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((self.bits >> Self::MSAA_SHIFT_BITS) & Self::MSAA_MASK_BITS) + 1
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1 << ((self.bits >> Self::MSAA_SHIFT_BITS) & Self::MSAA_MASK_BITS)
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}
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pub fn from_primitive_topology(primitive_topology: PrimitiveTopology) -> Self {
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let primitive_topology_bits = ((primitive_topology as u32)
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& Self::PRIMITIVE_TOPOLOGY_MASK_BITS)
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<< Self::PRIMITIVE_TOPOLOGY_SHIFT_BITS;
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Mesh2dPipelineKey::from_bits(primitive_topology_bits).unwrap()
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Self::from_bits(primitive_topology_bits).unwrap()
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}
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pub fn primitive_topology(&self) -> PrimitiveTopology {
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@ -90,25 +90,26 @@ impl FromWorld for SpritePipeline {
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bitflags::bitflags! {
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#[repr(transparent)]
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// NOTE: Apparently quadro drivers support up to 64x MSAA.
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// MSAA uses the highest 6 bits for the MSAA sample count - 1 to support up to 64x MSAA.
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// MSAA uses the highest 3 bits for the MSAA log2(sample count) to support up to 128x MSAA.
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pub struct SpritePipelineKey: u32 {
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const NONE = 0;
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const COLORED = (1 << 0);
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const MSAA_RESERVED_BITS = SpritePipelineKey::MSAA_MASK_BITS << SpritePipelineKey::MSAA_SHIFT_BITS;
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const MSAA_RESERVED_BITS = Self::MSAA_MASK_BITS << Self::MSAA_SHIFT_BITS;
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}
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}
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impl SpritePipelineKey {
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const MSAA_MASK_BITS: u32 = 0b111111;
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const MSAA_SHIFT_BITS: u32 = 32 - 6;
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const MSAA_MASK_BITS: u32 = 0b111;
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const MSAA_SHIFT_BITS: u32 = 32 - Self::MSAA_MASK_BITS.count_ones();
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pub fn from_msaa_samples(msaa_samples: u32) -> Self {
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let msaa_bits = ((msaa_samples - 1) & Self::MSAA_MASK_BITS) << Self::MSAA_SHIFT_BITS;
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SpritePipelineKey::from_bits(msaa_bits).unwrap()
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let msaa_bits =
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(msaa_samples.trailing_zeros() & Self::MSAA_MASK_BITS) << Self::MSAA_SHIFT_BITS;
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Self::from_bits(msaa_bits).unwrap()
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}
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pub fn msaa_samples(&self) -> u32 {
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((self.bits >> Self::MSAA_SHIFT_BITS) & Self::MSAA_MASK_BITS) + 1
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1 << ((self.bits >> Self::MSAA_SHIFT_BITS) & Self::MSAA_MASK_BITS)
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}
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}
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