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Reduce additions and use Unsafe.As

af/merge-core
James Jackson-South 8 years ago
parent
07d52846f3
commit
ef8610e835
2 changed files with 87 additions and 43 deletions
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  1. 102
      src/ImageSharp/Formats/Jpeg/PdfJsPort/Components/PdfJsIDCT.cs
  2. 28
      tests/ImageSharp.Benchmarks/General/StructCasting.cs

102
src/ImageSharp/Formats/Jpeg/PdfJsPort/Components/PdfJsIDCT.cs
View File

@ -43,15 +43,23 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
// inverse DCT on rows
for (int row = 0; row < 64; row += 8)
{
int r1 = row + 1;
int r2 = row + 2;
int r3 = row + 3;
int r4 = row + 4;
int r5 = row + 5;
int r6 = row + 6;
int r7 = row + 7;
// gather block data
p0 = Unsafe.Add(ref blockDataRef, row);
p1 = Unsafe.Add(ref blockDataRef, row + 1);
p2 = Unsafe.Add(ref blockDataRef, row + 2);
p3 = Unsafe.Add(ref blockDataRef, row + 3);
p4 = Unsafe.Add(ref blockDataRef, row + 4);
p5 = Unsafe.Add(ref blockDataRef, row + 5);
p6 = Unsafe.Add(ref blockDataRef, row + 6);
p7 = Unsafe.Add(ref blockDataRef, row + 7);
p1 = Unsafe.Add(ref blockDataRef, r1);
p2 = Unsafe.Add(ref blockDataRef, r2);
p3 = Unsafe.Add(ref blockDataRef, r3);
p4 = Unsafe.Add(ref blockDataRef, r4);
p5 = Unsafe.Add(ref blockDataRef, r5);
p6 = Unsafe.Add(ref blockDataRef, r6);
p7 = Unsafe.Add(ref blockDataRef, r7);
// dequant p0
p0 *= Unsafe.Add(ref quantizationTableRef, row);
@ -62,24 +70,24 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
t = ((DctSqrt2 * p0) + 512) >> 10;
short st = (short)t;
Unsafe.Add(ref computationBufferRef, row) = st;
Unsafe.Add(ref computationBufferRef, row + 1) = st;
Unsafe.Add(ref computationBufferRef, row + 2) = st;
Unsafe.Add(ref computationBufferRef, row + 3) = st;
Unsafe.Add(ref computationBufferRef, row + 4) = st;
Unsafe.Add(ref computationBufferRef, row + 5) = st;
Unsafe.Add(ref computationBufferRef, row + 6) = st;
Unsafe.Add(ref computationBufferRef, row + 7) = st;
Unsafe.Add(ref computationBufferRef, r1) = st;
Unsafe.Add(ref computationBufferRef, r2) = st;
Unsafe.Add(ref computationBufferRef, r3) = st;
Unsafe.Add(ref computationBufferRef, r4) = st;
Unsafe.Add(ref computationBufferRef, r5) = st;
Unsafe.Add(ref computationBufferRef, r6) = st;
Unsafe.Add(ref computationBufferRef, r7) = st;
continue;
}
// dequant p1 ... p7
p1 *= Unsafe.Add(ref quantizationTableRef, row + 1);
p2 *= Unsafe.Add(ref quantizationTableRef, row + 2);
p3 *= Unsafe.Add(ref quantizationTableRef, row + 3);
p4 *= Unsafe.Add(ref quantizationTableRef, row + 4);
p5 *= Unsafe.Add(ref quantizationTableRef, row + 5);
p6 *= Unsafe.Add(ref quantizationTableRef, row + 6);
p7 *= Unsafe.Add(ref quantizationTableRef, row + 7);
p1 *= Unsafe.Add(ref quantizationTableRef, r1);
p2 *= Unsafe.Add(ref quantizationTableRef, r2);
p3 *= Unsafe.Add(ref quantizationTableRef, r3);
p4 *= Unsafe.Add(ref quantizationTableRef, r4);
p5 *= Unsafe.Add(ref quantizationTableRef, r5);
p6 *= Unsafe.Add(ref quantizationTableRef, r6);
p7 *= Unsafe.Add(ref quantizationTableRef, r7);
// stage 4
v0 = ((DctSqrt2 * p0) + CenterJSample) >> 8;
@ -128,14 +136,22 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
// inverse DCT on columns
for (int col = 0; col < 8; ++col)
{
int c8 = col + 8;
int c16 = col + 16;
int c24 = col + 24;
int c32 = col + 32;
int c40 = col + 40;
int c48 = col + 48;
int c56 = col + 56;
p0 = Unsafe.Add(ref computationBufferRef, col);
p1 = Unsafe.Add(ref computationBufferRef, col + 8);
p2 = Unsafe.Add(ref computationBufferRef, col + 16);
p3 = Unsafe.Add(ref computationBufferRef, col + 24);
p4 = Unsafe.Add(ref computationBufferRef, col + 32);
p5 = Unsafe.Add(ref computationBufferRef, col + 40);
p6 = Unsafe.Add(ref computationBufferRef, col + 48);
p7 = Unsafe.Add(ref computationBufferRef, col + 56);
p1 = Unsafe.Add(ref computationBufferRef, c8);
p2 = Unsafe.Add(ref computationBufferRef, c16);
p3 = Unsafe.Add(ref computationBufferRef, c24);
p4 = Unsafe.Add(ref computationBufferRef, c32);
p5 = Unsafe.Add(ref computationBufferRef, c40);
p6 = Unsafe.Add(ref computationBufferRef, c48);
p7 = Unsafe.Add(ref computationBufferRef, c56);
// check for all-zero AC coefficients
if ((p1 | p2 | p3 | p4 | p5 | p6 | p7) == 0)
@ -147,13 +163,13 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
short st = (short)t;
Unsafe.Add(ref blockDataRef, col) = st;
Unsafe.Add(ref blockDataRef, col + 8) = st;
Unsafe.Add(ref blockDataRef, col + 16) = st;
Unsafe.Add(ref blockDataRef, col + 24) = st;
Unsafe.Add(ref blockDataRef, col + 32) = st;
Unsafe.Add(ref blockDataRef, col + 40) = st;
Unsafe.Add(ref blockDataRef, col + 48) = st;
Unsafe.Add(ref blockDataRef, col + 56) = st;
Unsafe.Add(ref blockDataRef, c8) = st;
Unsafe.Add(ref blockDataRef, c16) = st;
Unsafe.Add(ref blockDataRef, c24) = st;
Unsafe.Add(ref blockDataRef, c32) = st;
Unsafe.Add(ref blockDataRef, c40) = st;
Unsafe.Add(ref blockDataRef, c48) = st;
Unsafe.Add(ref blockDataRef, c56) = st;
continue;
}
@ -213,14 +229,14 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
p7 = (p7 < 16) ? 0 : (p7 >= 4080) ? MaxJSample : p7 >> 4;
// store block data
Unsafe.Add(ref blockDataRef, col) = (short)p0;
Unsafe.Add(ref blockDataRef, col + 8) = (short)p1;
Unsafe.Add(ref blockDataRef, col + 16) = (short)p2;
Unsafe.Add(ref blockDataRef, col + 24) = (short)p3;
Unsafe.Add(ref blockDataRef, col + 32) = (short)p4;
Unsafe.Add(ref blockDataRef, col + 40) = (short)p5;
Unsafe.Add(ref blockDataRef, col + 48) = (short)p6;
Unsafe.Add(ref blockDataRef, col + 56) = (short)p7;
Unsafe.Add(ref blockDataRef, col) = Unsafe.As<int, short>(ref Unsafe.AsRef(p0));
Unsafe.Add(ref blockDataRef, c8) = Unsafe.As<int, short>(ref Unsafe.AsRef(p1));
Unsafe.Add(ref blockDataRef, c16) = Unsafe.As<int, short>(ref Unsafe.AsRef(p2));
Unsafe.Add(ref blockDataRef, c24) = Unsafe.As<int, short>(ref Unsafe.AsRef(p3));
Unsafe.Add(ref blockDataRef, c32) = Unsafe.As<int, short>(ref Unsafe.AsRef(p4));
Unsafe.Add(ref blockDataRef, c40) = Unsafe.As<int, short>(ref Unsafe.AsRef(p5));
Unsafe.Add(ref blockDataRef, c48) = Unsafe.As<int, short>(ref Unsafe.AsRef(p6));
Unsafe.Add(ref blockDataRef, c56) = Unsafe.As<int, short>(ref Unsafe.AsRef(p7));
}
}
}

28
tests/ImageSharp.Benchmarks/General/StructCasting.cs
View File

@ -0,0 +1,28 @@
using System.Runtime.CompilerServices;
using BenchmarkDotNet.Attributes;
namespace SixLabors.ImageSharp.Benchmarks.General
{
public class StructCasting
{
[Benchmark(Baseline = true)]
public short ExplicitCast()
{
int x = 5 * 2;
return (short)x;
}
[Benchmark]
public short UnsafeCast()
{
int x = 5 * 2;
return Unsafe.As<int, short>(ref x);
}
[Benchmark]
public short UnsafeCastRef()
{
return Unsafe.As<int, short>(ref Unsafe.AsRef(5 * 2));
}
}
}
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