Component shuffling for RGB(A)-like formats with SIMD Intrinsics

[antonfirsov]

We need cheap bulk-conversion between the following formats:
Argb32, Bgra32, Rgba32, Bgr24, Rgb24

We are especially interested in Rgb24, Bgr24 <=> Rgba32. I'm having sweat dreams about a community PR dealing with this problem. Should be easy for anyone having basic knowledge of System.Runtime.Intrinsics.

Implementation should be added to new span-based methods in PixelConverter.cs, those could be invoked than from T4 generated PixelOperations<TPixel> implementors like here:
https://github.com/SixLabors/ImageSharp/blob/78a584e8482b052d7a9885682299e2f37518d83d/src/ImageSharp/PixelFormats/PixelImplementations/Generated/Rgb24.PixelOperations.Generated.cs

If a PR would only add the PixelConverter helpers + tests, I'm happy to provide guidance or even finish the code for the rest of the work.

@john-h-k @Sergio0694 any chance you are interested?

Tasks:

• Add 4=>4 channel shuffling methods to SimdUtils
• Add 3=>4 channel shuffling methods to SimdUtils
• Add 4=>3 channel shuffling methods to SimdUtils
• Update Rgba32 compatible pixel operations to utilize new shuffle methods.
• Update Rgb24 compatible pixel operations to utilize new shuffle methods.

[JimBobSquarePants]

I'm gonna have a look at this.

[antonfirsov]

Btw, the Span<Vector4> <=> Span<TPixel> conversions are delegating the (pad/slice) shuffle work to PixelOperations<TPixel> conversion methods:

https://github.com/SixLabors/ImageSharp/blob/78a584e8482b052d7a9885682299e2f37518d83d/src/ImageSharp/PixelFormats/Utils/Vector4Converters.RgbaCompatible.cs

Which means that the last two steps will be done automatically, if I'm not missing anything. Can't wait to see the Vector4 <=> Rgb24 before/after comparison. (Which is the main goal of this issue because of the conversion steps in Jpeg decoder and ResizeProcessor.)

[JimBobSquarePants]

@antonfirsov need to add a specific benchmark for that but I know for certain that even my Rgba32 <==> Rgb24 fallback is a lot faster than the original.

[JimBobSquarePants]

@antonfirsov Here you go!

ToVector4_Rgb24

BenchmarkDotNet=v0.12.1, OS=Windows 10.0.19041.572 (2004/?/20H1)
Intel Core i7-8650U CPU 1.90GHz (Kaby Lake R), 1 CPU, 8 logical and 4 physical cores
.NET Core SDK=3.1.403
  [Host]     : .NET Core 3.1.9 (CoreCLR 4.700.20.47201, CoreFX 4.700.20.47203), X64 RyuJIT
  Job-OIBEDX : .NET Framework 4.8 (4.8.4250.0), X64 RyuJIT
  Job-OPAORC : .NET Core 2.1.23 (CoreCLR 4.6.29321.03, CoreFX 4.6.29321.01), X64 RyuJIT
  Job-VPSIRL : .NET Core 3.1.9 (CoreCLR 4.700.20.47201, CoreFX 4.700.20.47203), X64 RyuJIT

IterationCount=3  LaunchCount=1  WarmupCount=3

Master

Method	Job	Runtime	Count	Mean	Error	StdDev	Ratio	RatioSD	Gen 0	Gen 1	Gen 2	Allocated
PixelOperations_Base	Job-BPVKME	.NET 4.7.2	64	278.4 ns	6.89 ns	0.38 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-BPVKME	.NET 4.7.2	64	310.2 ns	87.58 ns	4.80 ns	1.11	0.02	-	-	-	-
PixelOperations_Base	Job-FBIBGB	.NET Core 2.1	64	231.9 ns	254.31 ns	13.94 ns	1.00	0.00	0.0052	-	-	24 B
PixelOperations_Specialized	Job-FBIBGB	.NET Core 2.1	64	230.2 ns	27.06 ns	1.48 ns	0.99	0.05	-	-	-	-
PixelOperations_Base	Job-CETXPV	.NET Core 3.1	64	215.5 ns	52.24 ns	2.86 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-CETXPV	.NET Core 3.1	64	236.7 ns	553.01 ns	30.31 ns	1.10	0.13	-	-	-	-
PixelOperations_Base	Job-BPVKME	.NET 4.7.2	256	1,022.3 ns	3,570.70 ns	195.72 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-BPVKME	.NET 4.7.2	256	622.5 ns	26.76 ns	1.47 ns	0.62	0.11	-	-	-	-
PixelOperations_Base	Job-FBIBGB	.NET Core 2.1	256	762.3 ns	103.78 ns	5.69 ns	1.00	0.00	0.0048	-	-	24 B
PixelOperations_Specialized	Job-FBIBGB	.NET Core 2.1	256	498.1 ns	70.87 ns	3.88 ns	0.65	0.00	-	-	-	-
PixelOperations_Base	Job-CETXPV	.NET Core 3.1	256	754.0 ns	37.92 ns	2.08 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-CETXPV	.NET Core 3.1	256	436.8 ns	21.88 ns	1.20 ns	0.58	0.00	-	-	-	-
PixelOperations_Base	Job-BPVKME	.NET 4.7.2	2048	5,679.3 ns	1,454.37 ns	79.72 ns	1.00	0.00	-	-	-	24 B
PixelOperations_Specialized	Job-BPVKME	.NET 4.7.2	2048	3,460.6 ns	273.43 ns	14.99 ns	0.61	0.01	-	-	-	-
PixelOperations_Base	Job-FBIBGB	.NET Core 2.1	2048	6,033.8 ns	8,785.67 ns	481.57 ns	1.00	0.00	-	-	-	24 B
PixelOperations_Specialized	Job-FBIBGB	.NET Core 2.1	2048	3,421.3 ns	376.64 ns	20.64 ns	0.57	0.04	-	-	-	-
PixelOperations_Base	Job-CETXPV	.NET Core 3.1	2048	5,542.3 ns	790.31 ns	43.32 ns	1.00	0.00	-	-	-	24 B
PixelOperations_Specialized	Job-CETXPV	.NET Core 3.1	2048	2,972.2 ns	70.72 ns	3.88 ns	0.54	0.00	-	-	-	-

Branch

Method	Job	Runtime	Count	Mean	Error	StdDev	Ratio	RatioSD	Gen 0	Gen 1	Gen 2	Allocated
PixelOperations_Base	Job-OIBEDX	.NET 4.7.2	64	298.4 ns	33.63 ns	1.84 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-OIBEDX	.NET 4.7.2	64	355.5 ns	908.51 ns	49.80 ns	1.19	0.17	-	-	-	-
PixelOperations_Base	Job-OPAORC	.NET Core 2.1	64	220.1 ns	13.77 ns	0.75 ns	1.00	0.00	0.0055	-	-	24 B
PixelOperations_Specialized	Job-OPAORC	.NET Core 2.1	64	228.5 ns	41.41 ns	2.27 ns	1.04	0.01	-	-	-	-
PixelOperations_Base	Job-VPSIRL	.NET Core 3.1	64	213.6 ns	12.47 ns	0.68 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-VPSIRL	.NET Core 3.1	64	217.0 ns	9.95 ns	0.55 ns	1.02	0.01	-	-	-	-
PixelOperations_Base	Job-OIBEDX	.NET 4.7.2	256	829.0 ns	242.93 ns	13.32 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-OIBEDX	.NET 4.7.2	256	448.9 ns	4.04 ns	0.22 ns	0.54	0.01	-	-	-	-
PixelOperations_Base	Job-OPAORC	.NET Core 2.1	256	863.0 ns	1,253.26 ns	68.70 ns	1.00	0.00	0.0048	-	-	24 B
PixelOperations_Specialized	Job-OPAORC	.NET Core 2.1	256	309.2 ns	66.16 ns	3.63 ns	0.36	0.03	-	-	-	-
PixelOperations_Base	Job-VPSIRL	.NET Core 3.1	256	737.0 ns	253.90 ns	13.92 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-VPSIRL	.NET Core 3.1	256	212.3 ns	1.07 ns	0.06 ns	0.29	0.01	-	-	-	-
PixelOperations_Base	Job-OIBEDX	.NET 4.7.2	2048	5,625.6 ns	404.35 ns	22.16 ns	1.00	0.00	-	-	-	24 B
PixelOperations_Specialized	Job-OIBEDX	.NET 4.7.2	2048	1,974.1 ns	229.84 ns	12.60 ns	0.35	0.00	-	-	-	-
PixelOperations_Base	Job-OPAORC	.NET Core 2.1	2048	5,467.2 ns	537.29 ns	29.45 ns	1.00	0.00	-	-	-	24 B
PixelOperations_Specialized	Job-OPAORC	.NET Core 2.1	2048	1,985.5 ns	4,714.23 ns	258.40 ns	0.36	0.05	-	-	-	-
PixelOperations_Base	Job-VPSIRL	.NET Core 3.1	2048	5,888.2 ns	1,622.23 ns	88.92 ns	1.00	0.00	-	-	-	24 B
PixelOperations_Specialized	Job-VPSIRL	.NET Core 3.1	2048	1,165.0 ns	191.71 ns	10.51 ns	0.20	0.00	-	-	-	-

FromVector4_Rgb24

BenchmarkDotNet=v0.12.1, OS=Windows 10.0.19041.572 (2004/?/20H1)
Intel Core i7-8650U CPU 1.90GHz (Kaby Lake R), 1 CPU, 8 logical and 4 physical cores
.NET Core SDK=3.1.403
  [Host]     : .NET Core 3.1.9 (CoreCLR 4.700.20.47201, CoreFX 4.700.20.47203), X64 RyuJIT
  Job-XYEQXL : .NET Framework 4.8 (4.8.4250.0), X64 RyuJIT
  Job-HSXNJV : .NET Core 2.1.23 (CoreCLR 4.6.29321.03, CoreFX 4.6.29321.01), X64 RyuJIT
  Job-YUREJO : .NET Core 3.1.9 (CoreCLR 4.700.20.47201, CoreFX 4.700.20.47203), X64 RyuJIT

IterationCount=3  LaunchCount=1  WarmupCount=3

Master

Method	Job	Runtime	Count	Mean	Error	StdDev	Ratio	RatioSD	Gen 0	Gen 1	Gen 2	Allocated
PixelOperations_Base	Job-BPNZYS	.NET 4.7.2	64	317.7 ns	125.40 ns	6.87 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-BPNZYS	.NET 4.7.2	64	316.4 ns	70.42 ns	3.86 ns	1.00	0.03	-	-	-	-
PixelOperations_Base	Job-NYROHY	.NET Core 2.1	64	232.7 ns	82.61 ns	4.53 ns	1.00	0.00	0.0055	-	-	24 B
PixelOperations_Specialized	Job-NYROHY	.NET Core 2.1	64	238.9 ns	106.11 ns	5.82 ns	1.03	0.01	-	-	-	-
PixelOperations_Base	Job-LSNAID	.NET Core 3.1	64	228.4 ns	15.16 ns	0.83 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-LSNAID	.NET Core 3.1	64	250.3 ns	22.79 ns	1.25 ns	1.10	0.01	-	-	-	-
PixelOperations_Base	Job-BPNZYS	.NET 4.7.2	256	975.5 ns	1,646.67 ns	90.26 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-BPNZYS	.NET 4.7.2	256	1,051.3 ns	170.43 ns	9.34 ns	1.08	0.11	0.0172	-	-	72 B
PixelOperations_Base	Job-NYROHY	.NET Core 2.1	256	793.0 ns	69.24 ns	3.80 ns	1.00	0.00	0.0048	-	-	24 B
PixelOperations_Specialized	Job-NYROHY	.NET Core 2.1	256	846.8 ns	117.07 ns	6.42 ns	1.07	0.01	0.0172	-	-	72 B
PixelOperations_Base	Job-LSNAID	.NET Core 3.1	256	797.2 ns	342.02 ns	18.75 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-LSNAID	.NET Core 3.1	256	640.2 ns	19.74 ns	1.08 ns	0.80	0.02	0.0172	-	-	72 B
PixelOperations_Base	Job-BPNZYS	.NET 4.7.2	2048	6,178.4 ns	1,537.81 ns	84.29 ns	1.00	0.00	-	-	-	24 B
PixelOperations_Specialized	Job-BPNZYS	.NET 4.7.2	2048	4,551.2 ns	257.65 ns	14.12 ns	0.74	0.01	0.0153	-	-	72 B
PixelOperations_Base	Job-NYROHY	.NET Core 2.1	2048	6,621.8 ns	13,533.62 ns	741.82 ns	1.00	0.00	-	-	-	24 B
PixelOperations_Specialized	Job-NYROHY	.NET Core 2.1	2048	4,390.4 ns	184.24 ns	10.10 ns	0.67	0.07	0.0153	-	-	72 B
PixelOperations_Base	Job-LSNAID	.NET Core 3.1	2048	6,357.9 ns	964.20 ns	52.85 ns	1.00	0.00	-	-	-	24 B
PixelOperations_Specialized	Job-LSNAID	.NET Core 3.1	2048	2,979.4 ns	132.81 ns	7.28 ns	0.47	0.00	0.0153	-	-	72 B

Branch

Method	Job	Runtime	Count	Mean	Error	StdDev	Ratio	RatioSD	Gen 0	Gen 1	Gen 2	Allocated
PixelOperations_Base	Job-XYEQXL	.NET 4.7.2	64	343.2 ns	305.91 ns	16.77 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-XYEQXL	.NET 4.7.2	64	320.8 ns	19.93 ns	1.09 ns	0.94	0.05	-	-	-	-
PixelOperations_Base	Job-HSXNJV	.NET Core 2.1	64	234.3 ns	17.98 ns	0.99 ns	1.00	0.00	0.0052	-	-	24 B
PixelOperations_Specialized	Job-HSXNJV	.NET Core 2.1	64	246.0 ns	82.34 ns	4.51 ns	1.05	0.02	-	-	-	-
PixelOperations_Base	Job-YUREJO	.NET Core 3.1	64	222.3 ns	39.46 ns	2.16 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-YUREJO	.NET Core 3.1	64	243.4 ns	33.58 ns	1.84 ns	1.09	0.01	-	-	-	-
PixelOperations_Base	Job-XYEQXL	.NET 4.7.2	256	824.9 ns	32.77 ns	1.80 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-XYEQXL	.NET 4.7.2	256	967.0 ns	39.09 ns	2.14 ns	1.17	0.01	0.0172	-	-	72 B
PixelOperations_Base	Job-HSXNJV	.NET Core 2.1	256	756.9 ns	94.43 ns	5.18 ns	1.00	0.00	0.0048	-	-	24 B
PixelOperations_Specialized	Job-HSXNJV	.NET Core 2.1	256	1,003.3 ns	3,192.09 ns	174.97 ns	1.32	0.22	0.0172	-	-	72 B
PixelOperations_Base	Job-YUREJO	.NET Core 3.1	256	748.6 ns	248.03 ns	13.60 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-YUREJO	.NET Core 3.1	256	437.0 ns	36.48 ns	2.00 ns	0.58	0.01	0.0172	-	-	72 B
PixelOperations_Base	Job-XYEQXL	.NET 4.7.2	2048	5,751.6 ns	704.24 ns	38.60 ns	1.00	0.00	-	-	-	24 B
PixelOperations_Specialized	Job-XYEQXL	.NET 4.7.2	2048	4,391.6 ns	718.17 ns	39.37 ns	0.76	0.00	0.0153	-	-	72 B
PixelOperations_Base	Job-HSXNJV	.NET Core 2.1	2048	6,202.0 ns	1,815.18 ns	99.50 ns	1.00	0.00	-	-	-	24 B
PixelOperations_Specialized	Job-HSXNJV	.NET Core 2.1	2048	4,225.6 ns	1,004.03 ns	55.03 ns	0.68	0.01	0.0153	-	-	72 B
PixelOperations_Base	Job-YUREJO	.NET Core 3.1	2048	6,157.1 ns	2,516.98 ns	137.96 ns	1.00	0.00	-	-	-	24 B
PixelOperations_Specialized	Job-YUREJO	.NET Core 3.1	2048	1,822.7 ns	1,764.43 ns	96.71 ns	0.30	0.02	0.0172	-	-	72 B

[JimBobSquarePants]

@antonfirsov Pushed an update that affects FromVector4_Rgb24 based on a suggestion by @Sergio0694 and It's squeezed a few more percentage performance.

Method	Job	Runtime	Count	Mean	Error	StdDev	Ratio	RatioSD	Gen 0	Gen 1	Gen 2	Allocated
PixelOperations_Base	Job-RPFDIH	.NET 4.7.2	64	327.7 ns	179.42 ns	9.83 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-RPFDIH	.NET 4.7.2	64	320.8 ns	21.37 ns	1.17 ns	0.98	0.03	-	-	-	-
PixelOperations_Base	Job-QSMZGQ	.NET Core 2.1	64	254.8 ns	337.29 ns	18.49 ns	1.00	0.00	0.0052	-	-	24 B
PixelOperations_Specialized	Job-QSMZGQ	.NET Core 2.1	64	245.3 ns	37.22 ns	2.04 ns	0.97	0.07	-	-	-	-
PixelOperations_Base	Job-YJZMFY	.NET Core 3.1	64	232.2 ns	189.28 ns	10.37 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-YJZMFY	.NET Core 3.1	64	255.4 ns	52.39 ns	2.87 ns	1.10	0.04	-	-	-	-
PixelOperations_Base	Job-RPFDIH	.NET 4.7.2	256	910.1 ns	293.07 ns	16.06 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-RPFDIH	.NET 4.7.2	256	974.4 ns	490.48 ns	26.89 ns	1.07	0.05	0.0172	-	-	72 B
PixelOperations_Base	Job-QSMZGQ	.NET Core 2.1	256	849.7 ns	1,654.73 ns	90.70 ns	1.00	0.00	0.0048	-	-	24 B
PixelOperations_Specialized	Job-QSMZGQ	.NET Core 2.1	256	759.9 ns	77.06 ns	4.22 ns	0.90	0.09	0.0172	-	-	72 B
PixelOperations_Base	Job-YJZMFY	.NET Core 3.1	256	816.1 ns	56.07 ns	3.07 ns	1.00	0.00	0.0057	-	-	24 B
PixelOperations_Specialized	Job-YJZMFY	.NET Core 3.1	256	493.0 ns	216.79 ns	11.88 ns	0.60	0.01	0.0172	-	-	72 B
PixelOperations_Base	Job-RPFDIH	.NET 4.7.2	2048	6,394.6 ns	2,077.05 ns	113.85 ns	1.00	0.00	-	-	-	24 B
PixelOperations_Specialized	Job-RPFDIH	.NET 4.7.2	2048	4,139.6 ns	276.41 ns	15.15 ns	0.65	0.01	0.0153	-	-	72 B
PixelOperations_Base	Job-QSMZGQ	.NET Core 2.1	2048	6,249.9 ns	799.28 ns	43.81 ns	1.00	0.00	-	-	-	24 B
PixelOperations_Specialized	Job-QSMZGQ	.NET Core 2.1	2048	4,020.5 ns	3,211.19 ns	176.02 ns	0.64	0.03	0.0153	-	-	72 B
PixelOperations_Base	Job-YJZMFY	.NET Core 3.1	2048	6,403.5 ns	4,626.86 ns	253.61 ns	1.00	0.00	-	-	-	24 B
PixelOperations_Specialized	Job-YJZMFY	.NET Core 3.1	2048	1,588.3 ns	912.20 ns	50.00 ns	0.25	0.01	0.0172	-	-	72 B